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Bogemans, Frieda, Mathieu Boudin, Rindert Janssens e Cecile Baeteman. "New data on the sedimentary processes and timing of the initial inundation of Lower Khuzestan (SW Iran) by the Persian Gulf". Holocene 27, n.º 4 (3 de outubro de 2016): 613–20. http://dx.doi.org/10.1177/0959683616670224.
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The early- and mid-Holocene deposits of the Lower Khuzestan plain at the north-eastern margin of the Persian Gulf have been investigated by means of facies analysis of sediment successions of undisturbed cores. Organic material and molluscs have been selected for dating by radiocarbon whereby possible contamination by hard-water effect is discussed. The results suggest that the Holocene transgression in Mesopotamia may have taken place later than generally accepted. Before ca. 7700–7900 yr cal. BP, the plain was characterized by mud-dominated fluvial systems. During the mid-Holocene, tides invaded the existing valleys, and the sedimentary environment shifted from fluvial to estuarine but not as extensively as has previously been suggested. The estuarine environments lasted for about 2000–2500 years until ca. 4850–5000 yr cal. BP when the seaward part of the plain was again characterized by widespread fluvial sedimentation.
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Gil-Díaz, Teba, Jörg Schäfer, Lionel Dutruch, Cécile Bossy, Frédérique Pougnet, Melina Abdou, Antoine Lerat-Hardy et al. "Tellurium behaviour in a major European fluvial–estuarine system (Gironde, France): fluxes, solid/liquid partitioning and bioaccumulation in wild oysters". Environmental Chemistry 16, n.º 4 (2019): 229. http://dx.doi.org/10.1071/en18226.
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Environmental contextThe environmental behaviour of tellurium is poorly understood. We investigate the transport of tellurium in both dissolved and particulate forms from the river watershed to the Gironde Estuary, where a 30-year historical record provides insight on tellurium bioaccumulation in wild oysters. These results constitute the first comprehensive study on natural tellurium behaviour in a major fluvial-estuarine system, information essential for predictive modelling of tellurium risk assessment. AbstractTellurium (Te) is a technology critical element (TCE) with largely unknown environmental behaviour, especially in continent-ocean interface systems. The unknown behaviour results from the lack of studies in aquatic environments and from analytical challenges limiting the determination of its naturally low (ultra-trace) environmental levels. We performed a comprehensive study of Te in the Lot–Garonne–Gironde fluvial–estuarine system to better understand seasonal variations, solid/liquid partitioning (Kd), gross fluxes, estuarine dynamics, and transfer to wild oysters at the estuary mouth. A temporal record (2014–2017) of dissolved (Ted) and particulate (Tep) Te concentrations at five sites in the Lot–Garonne River system shows little differences between sites, with average ~0.9ngL−1 and ~50µgkg−1 respective concentrations. Watershed Ted and Tep follow parallel seasonal patterns, which result in constant partitioning (log10 Kd ~4.75Lkg−1), with constant annual gross dissolved fluxes (~15.0kgy−1) and variable gross particulate fluxes (from 6.50 to 140kgy−1) entering the Gironde Estuary. Estuarine reactivity in contrasting hydrological conditions (from flood to drought) suggest that grain-size effects and/or estuarine hydrological residence times strongly affect Tep behaviour. Historical records (1984–2017) of Te in wild oysters at the estuary mouth vary from 1.33 to 2.89µgkg−1 dry weight (d.w.), without any clear long-term trend. This study provides rare knowledge on Te environmental dynamics in aquatic systems, and suggests that, although no current anthropogenic sources were identified in the economically developed Lot-Garonne-Gironde fluvial-estuarine system, there is a non-negligible bioaccumulation in wild oysters at the estuary mouth.
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Keough, Brandon, e Kenneth Ridgway. "High-Latitude Depositional Systems, Provenance, and Basinal Setting of the Late Cretaceous Cantwell Basin, Denali National Park and Preserve, Alaska: A Stratigraphic Framework for Paleontological and Paleoclimatic Studies". Geosciences 13, n.º 6 (15 de junho de 2023): 181. http://dx.doi.org/10.3390/geosciences13060181.
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The Cantwell Formation of the central Alaska Range provides a robust archive of high-latitude, Late Cretaceous depositional systems and paleo-floral/faunal assemblages. Our stratigraphic analysis defines two mappable members. The lower member (1500–2000 m thick) represents vegetated alluvial fan and braided fluvial systems that transition up-section to fluvial–estuarine systems that drained into an inland continental seaway. The upper member (~2000 m thick) represents estuarine–marginal marine and lacustrine systems. Previous paleontological studies demonstrate that the Cantwell basin was populated by various dinosaurs, fishes, bivalves, birds, and marginal marine micro-organisms. Integration of new and published geologic mapping allows for reconstruction of depositional systems at the basin scale and provides additional paleogeographic context. The northern basin margin was defined by a previously unrecognized south-verging thrust belt, whereas the southern margin of the basin was defined by a north-verging thrust belt inboard of an active magmatic arc. Sediment sources interpreted from U-Pb detrital zircon geochronology included the coeval magmatic arc and older Cretaceous plutons, and Proterozoic–Mesozoic strata exhumed along the basin margins. Results of our study provide a depositional, stratigraphic, and structural framework that may serve as a guide for future paleontological and paleoclimatic investigations of Late Cretaceous Arctic environments of the Cantwell basin.
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Jalón-Rojas, I., S. Schmidt e A. Sottolichio. "Turbidity in the fluvial Gironde Estuary (S–W France) based on 10 year continuous monitoring: sensitivity to hydrological conditions". Hydrology and Earth System Sciences Discussions 12, n.º 3 (10 de março de 2015): 2843–83. http://dx.doi.org/10.5194/hessd-12-2843-2015.
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Abstract. Climate change and human activities impact the volume and timing of freshwater input to estuaries. These modifications in fluvial discharges are expected to influence estuarine suspended sediment dynamics, and in particular the turbidity maximum zone (TMZ). Located in the southwest France, the Gironde fluvial-estuarine systems has an ideal context to address this issue. It is characterized by a very pronounced TMZ, a decrease in mean annual runoff in the last decade, and it is quite unique in having a long-term and high-frequency monitoring of turbidity. The effect of tide and river flow on turbidity in the fluvial estuary is detailed, focusing on dynamics related to changes in hydrological conditions (river floods, periods of low-water, inter-annual changes). Turbidity shows hysteresis loops at different time scales: during river floods and over the transitional period between the installation and expulsion of the TMZ. These hysteresis patterns, that reveal the origin of sediment, locally resuspended or transported from the watershed, may be a tool to evaluate the presence of remained mud. Statistics on turbidity data bound the range of river flow that promotes the TMZ installation in the fluvial stations. Hydrological indicators of the persistence and turbidity level of the TMZ are also defined. The long-term evolution of these indicators confirms the influence of discharge decrease on the intensification of the TMZ in tidal rivers, and provides a tool to evaluate future scenarios.
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Fitch, Simon, Ken Thomson e Vince Gaffney. "Late Pleistocene and Holocene depositional systems and the palaeogeography of the Dogger Bank, North Sea". Quaternary Research 64, n.º 2 (setembro de 2005): 185–96. http://dx.doi.org/10.1016/j.yqres.2005.03.007.
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Abstract3D seismic data from the Dogger Bank, North Sea, allow the mapping of Late Pleistocene and Holocene depositional systems in unprecedented detail. The data demonstrate that glacial processes resulted in the development of incised tunnel valley systems during the Weichselian and that these were subsequently modified by fluvial processes in a pro-glacial setting. Subsequently, the Dogger Bank formed an emergent plain during the Holocene with a complex meandering river system, associated tributary or distributary channels and lakes, dominating the region. Prior to the sea level rising sufficiently to submerge the Dogger Bank around 7500 yr ago, the meandering river system was replaced by a dendritic channel network of potential fluvial, estuarine or intertidal origin. As the Holocene depositional features bear no systematic relationship to the bathymetry this study demonstrates that previously published bathymetry-based models for the Holocene palaeogeographic development of the North Sea require modification.
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Hayes, Derek A., Scott E. Botterill, Michael J. Ranger e Murray K. Gingras. "Fluvial character and architecture of an outcrop using sedimentology combined with UAV-based modeling, Cretaceous McMurray Formation, NE Alberta, Canada". Journal of Sedimentary Research 93, n.º 5 (23 de maio de 2023): 273–92. http://dx.doi.org/10.2110/jsr.2022.039.
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ABSTRACT It is widely accepted that most occurrences of inclined heterolithic stratification (IHS) in the rock record form by laterally accreting point bars in freshwater fluvial, tidally influenced fluvial, or tidally dominated estuary channels. Despite the widespread distribution of IHS in the subsurface and outcropping strata of the lower Cretaceous McMurray Formation, the large-scale depositional architecture and lateral facies variability of these deposits remains controversial. The relatively limited lateral extent of many of the outcrops is a challenge, particularly when point-bar deposits on the scale of hundreds of meters to kilometers are interpreted in outcrops spanning anywhere from 100 to 300 meters laterally. This has in turn led researchers to leverage other datasets such as 3-D seismic to analyze the large-scale depositional architecture of the IHS, leading to two main interpretations for the IHS in the McMurray Formation: 1) a fluvially dominated environment owing to geomorphological features comparable to those in large modern fluvial systems, or 2) an estuarine environment owing to the presence of trace fossils characteristic of marine-derived faunal colonization in brackish-water settings and strong evidence of tidal modulation. The purpose of this study is to investigate the sedimentology and depositional architecture of IHS in a unique, kilometer-wide outcrop exposure of McMurray Formation strata and compare it to IHS observed at other McMurray Formation outcrops previously interpreted as estuarine channels. This is achieved by combining traditional field-based methods with Unmanned Aerial Vehicle-based outcrop modeling to create a 3-D outcrop model to visualize and analyze large point-bar geobodies deposited in a channel upwards of 25 meters deep and 750 meters wide exposed in outcrop at Crooked Rapids of the Athabasca River, west of the City of Fort McMurray. Importantly, this methodology uses bed orientation trends, paleocurrent data, and sedimentological observations to identify and map architectural elements, which constitute an eastward-accreting point bar crosscut by a southwestward-accreting counter point bar in the outcrop. The results strongly suggest that the IHS at Crooked Rapids was deposited in a freshwater fluvial environment. When compared to IHS deposited in estuarine depositional environments, fluvial IHS is driven by seasonal river discharge as opposed to the interplay between river discharge and the extent of the tidal prism. Therefore, fluvial IHS is: 1) dominantly sandstone with very minor waning-flow siltstone interbeds resulting from erosion by the succeeding freshet phase, and 2) completely devoid of bioturbation until flat-lying bar top or overbank strata is encountered. Using 3-D outcrop modeling to supplement sedimentological and ichnological observations strengthens the interpretation of complex fluvial geobodies and increases the overall understanding of the large-scale depositional architecture of point bars across the tidal–fluvial transition zone.
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Selim, Selim Saber. "Sedimentology and stratigraphic evolution of fluvial–tidal transition reservoirs: an outcrop analog for the hydrocarbon-bearing Bahariya Formation, Western Desert, Egypt". Journal of Sedimentary Research 93, n.º 1 (18 de janeiro de 2023): 50–70. http://dx.doi.org/10.2110/jsr.2021.130.
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ABSTRACT The deposits of the tidal–fluvial transition zone are one of the most significant and complicated components of marginal marine systems. Sedimentological studies of these deposits are necessary due to their heterogeneous nature, which is controlled by competing tidal and fluvial parameters. Outcrop studies are required to understand the architecture, sedimentology, and evolution of tidal–fluvial deposits. The Cenomanian upper unit of the Bahariya Formation in the northern part of the Western Desert of Egypt is a tide-dominated fluvio-estuarine deposit sourced from crystalline basement and Early Cretaceous siliciclastic sedimentary rocks that lie to the southeast and south. Based on sedimentary facies analysis and paleocurrent data, the upper Bahariya Formation is composed of six main architectural elements: 1) river-dominated, tide-influenced point bar, 2) tide-dominated, river-influenced point bar, 3) floodplain, 4) crevasse splay, 5) crevasse channel, and 6) mud plug. These elements are stacked in a multistory tidal–fluvial channel complex and associated depositional elements. The reconstructed paleochannels trend from southeast to northwest, and migrated to the east and southeast. The relative contribution of fluvial processes decreased upwards through the stacked stories, with a corresponding increase in the contribution of tidal processes that were associated with transgression. An understanding of the architecture and sedimentology of the tidal–fluvial transition from outcrop successions allows the improved characterization of tidal–fluvial point-bar reservoirs and associated elements.
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Chalov, R. S., K. M. Berkovich, G. A. Larionov e L. F. Litvin. "Study of erosion-channel systems and its components: theory, history, and practice". Geomorphology RAS, n.º 2 (26 de abril de 2019): 95–108. http://dx.doi.org/10.31857/s0435-42812019295-108.
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The article is dedicated to the 50th anniversary since the N. I. Makkaveev’s Scientific Research Laboratory for soil erosion and channel processes was organized at the Moscow University. The history of scientific school, created by N. I. Makkaveev, establishment is considered, as well as the discipline on integral erosion-depositional process and its evolution to the theory of catchment erosion-fluvial systems. The analysis of the fundamental researches performed by the Laboratory is submitted, and the application tasks in the area of soil erosion, gully erosion, channel and estuarine processes are outlined. Main directions of research are formulated, the prospects for their development are evaluated.
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Mendes, Joana, Rui Ruela, Ana Picado, João Pedro Pinheiro, Américo Soares Ribeiro, Humberto Pereira e João Miguel Dias. "Modeling Dynamic Processes of Mondego Estuary and Óbidos Lagoon Using Delft3D". Journal of Marine Science and Engineering 9, n.º 1 (15 de janeiro de 2021): 91. http://dx.doi.org/10.3390/jmse9010091.
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Estuarine systems currently face increasing pressure due to population growth, rapid economic development, and the effect of climate change, which threatens the deterioration of their water quality. This study uses an open-source model of high transferability (Delft3D), to investigate the physics and water quality dynamics, spatial variability, and interrelation of two estuarine systems of the Portuguese west coast: Mondego Estuary and Óbidos Lagoon. In this context, the Delft3D was successfully implemented and validated for both systems through model-observation comparisons and further explored using realistically forced and process-oriented experiments. Model results show (1) high accuracy to predict the local hydrodynamics and fair accuracy to predict the transport and water quality of both systems; (2) the importance of the local geomorphology and estuary dimensions in the tidal propagation and asymmetry; (3) Mondego Estuary (except for the south arm) has a higher water volume exchange with the adjacent ocean when compared to Óbidos Lagoon, resulting from the highest fluvial discharge that contributes to a better water renewal; (4) the dissolved oxygen (DO) varies with water temperature and salinity differently for both systems. On the one hand, for Mondego Estuary during winter the DO levels mainly fluctuate with salinity. On the other hand, for Óbidos Lagoon, DO distribution is determined by both water temperature and salinity. During summer, the high residence time and water temperature limit the DO levels in both systems. The high transferability and superior stability of Delft3D make this model a foundation for realistic simulation and research of distinct estuarine systems, giving support to their maintenance and restoration.
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Shawler, Justin L., Christopher J. Hein, Elizabeth A. Canuel, James M. Kaste, Gregory G. Fitzsimons, Ioannis Y. Georgiou e Debra A. Willard. "Tidal erosion and upstream sediment trapping modulate records of land-use change in a formerly glaciated New England estuary". Anthropocene Coasts 2, n.º 1 (1 de janeiro de 2019): 340–61. http://dx.doi.org/10.1139/anc-2018-0034.
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Land clearing, river impoundments, and other human modifications to the upland landscape and within estuarine systems can drive coastal change at local to regional scales. However, as compared with mid-latitude coasts, the impacts of human modifications along sediment-starved formerly glaciated coastal landscapes are relatively understudied. To address this gap, we present a late-Holocene record of changing sediment accumulation rates and sediment sources from sediment cores collected across a tidal flat in the Merrimack River estuary (Mass., USA). We pair sedimentology, geochronology, bulk- and stable-isotope organic geochemistry, and hydrodynamic simulations with historical data to evaluate human and natural impacts on coastal sediment fluxes. During the 17th to 19th centuries, accumulation rates increased by an order of magnitude in the central tidal flat, likely in response to enhanced delivery of terrestrial sediment resulting from upland deforestation. However, the overall increase in accumulation (0.56–2.6 mm/year) within the estuary is subtle and spatially variable across the tidal flats because of coincident anthropogenic land clearing and dam building, upland sediment storage, and estuarine hydrodynamics. This study provides insight into the response of formerly glaciated fluvial-coastal systems to human modifications, and underscores the role of estuarine environmental conditions in modifying upland signals of land-use change.
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Nolin, M. C., e L. Lamontagne. "Fiabilité d'une étude pédologique détaillée réalisée en terrain plat". Canadian Journal of Soil Science 71, n.º 3 (1 de agosto de 1991): 339–53. http://dx.doi.org/10.4141/cjss91-033.
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In order to estimate the reliability of soil information presented in a detailed soil survey (1:20 000 scale) conducted in a flat terrain (Vercheres county, Quebec), 35 randomly selected delineations were inspected with 10 sites per delineation. Reliability was evaluated according to parent material (marine, estuarine and fluvial) and kind of map units (simple and compound). As a whole, mineral soils have been mapped and defined reliably for most criteria commonly used in soil interpretation systems. Reliability of soil information differed significatively with parent material. Taxonomic purity of marine, fluvial and estuarine soils delineations were 70, 58 and 28%, respectively. Although less precise, compound map units were more reliable than simple map units. Among the 13 soil variables studied, A and B horizons texture, B horizon designation and depth to carbonates were the more frequently in error. Results finally indicated that reliability is also a function of the delineation area and inspection density. In order to improve reliability of soil information and accelerate soil survey in future projects, it is suggested to adjust inspection density according to parent material, to reduce the number of classes for a few variables and to avoid excessive use of soil series'variants and delineations of small size (< 4 ha). Key words: Reliability, purity, accuracy, soil survey procedures, inspection density
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Phillips, Stephen P., John A. Howell, Adrian J. Hartley e Magda Chmielewska. "Tidal estuarine deposits of the transgressive Naturita Formation (Dakota Sandstone): San Rafael Swell, Utah, U.S.A." Journal of Sedimentary Research 90, n.º 8 (19 de agosto de 2020): 777–95. http://dx.doi.org/10.2110/jsr.2020.51.
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ABSTRACT Thin tidal estuarine deposits of the Naturita Formation (0–23 m) of the San Rafael Swell record the initial flooding of the Cretaceous Western Interior Seaway, Utah, and capture the transition from inland fluvial systems to fully marine conditions over a time period of 5 My or less. A tide-dominated estuarine environment is favored due to the combined presence of mud and/or carbonaceous drapes on ripples and dunes, bidirectional flow indicators, sigmoidal cross-stratification, herring-bone cross-stratification, and bimodal paleocurrent measurements. Facies associations are arranged in a predictable manner. Locally at the base of the Naturita Formation, tidally influenced fluvial channel deposits are present. These are overlain by tidal bars, including subtidal bars and intertidal point bars. Overlying the tidal bars are sand-flat and mud-flat deposits as well as bedded coal and carbonaceous mudstone that represents a supratidal setting in the estuary. The Formation can be capped by a thin transgressive lag composed of shell debris, and/or pebbles, that marks the final transition into the fully marine Tununk Shale Member of the overlying Mancos Shale. Lateral relationships between estuaries and adjacent paleohighs shed light on the influence of foreland-basin tectonics on the location and preservation of tide-dominated estuaries. Estuarine and shoreface deposits are absent along the eastern flank of the San Rafael Swell and eastward for more than 80 km. This zone of nondeposition or erosion is coincident with the location of the forebulge in the developing foreland basin, implying that growth of the forebulge prohibited the development of, or enhanced the later erosion of, estuarine deposits. Conversely, enhanced accommodation in the transition into the foredeep depozone allow the preservation of tide-dominated estuarine deposits along the western flank of the San Rafael Swell. Additionally, the possibility of a pre-Laramide tectonic history for the San Rafael Swell is indicated by a distinct lack of Naturita Formation deposits in an area that is coincident with the modern-day axis of the anticline. Overall, the Naturita records the initial flooding of the Western Interior Seaway in the San Rafael Swell region and provides an excellent case study of the deposits that are laid down in a transgressive system that passes from coastal-plain to offshore deposits.
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Issautier, Benoît, Yves-Michel Le Nindre, Abdullah Memesh, Saleh Dini e Sophie Viseur. "Managing clastic reservoir heterogeneity I: Sedimentology and sequence stratigraphy of the Late Triassic Minjur Sandstone at the Khashm al Khalta type locality, Central Saudi Arabia". GeoArabia 17, n.º 2 (1 de abril de 2012): 17–56. http://dx.doi.org/10.2113/geoarabia170217.
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ABSTRACT The Late Triassic (Norian–Rhaetian) Minjur Sandstone provides a remarkable case study for understanding and modelling the spatial distribution of sand bodies in a fluvial-deltaic system. As such it has been studied in connection with the geological storage of CO2 in complex heterogeneous formations. Detailed sedimentological mapping of the formation’s vertical and lateral variations in and around the type section at Khashm al Khalta (Khashm al Minjur), which is the area of interpreted maximum inlet/outlet activity, has provided a relatively detailed picture of the sequence stratigraphy. As originally described, shallow-marine flooding with the development of tidal mud flats and carbonate facies occurred near the middle of the formation, splitting it into a lower member dominated by subtidal, brackish and scattered fluvial environments, and an upper member marked by the appearance of meandering point bars capped upward by very proximal deposits forming thick (20 m) coarse-grained sandstone bars that can be followed over several kilometers. The general trend at formation scale is thus upward thickening and coarsening sedimentation related to an increasing clastic influx and the development of fluvial systems, with the fluvial upper member being dominated by amalgamated sand bars. The sequence stratigraphy indicates nine depositional sequences involving four depositional environments: sabkha, tidal, estuarine and fluvial-continental. The lower Minjur is a transgressive tract of four sequences of which Sequence 4 reflects maximum flooding and correlates with maximum flooding surface (MFS) Middle Norian Tr80. Sequence 5 corresponds to a meander system at the base of the upper Minjur, and is followed by sequences 6 to 9 reflecting an increasing clastic influx generating amalgamated coarse-grained bars. The upper Minjur thus represents a highstand systems tract.
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Wilmot, R. D. "Mineralogical evidence for sediment derivation and ice movement within the Wash drainage basin, eastern England". Clay Minerals 20, n.º 2 (junho de 1985): 209–20. http://dx.doi.org/10.1180/claymin.1985.020.2.05.
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AbstractThe Wash drainage basin contains four principal river systems. Samples were collected from the freshwater and estuarine reaches of each of these, and silt- and clay-grade fractions were separated and examined by XRD. The clay mineralogy of each of the rivers is different; in the north the Witham sediments contain chlorite, the Welland and Nene samples contain vermiculite, with a higher proportion of kaolinite in the former, while in the south the Ouse sediments contain smectite. The clay fractions of the samples from the estuarine reaches all contain chlorite, confirming that non-fluvial sources must contribute to the sediments of the Wash. Comparison of this pattern of clay mineralogy with that for the underlying Jurassic and Cretaceous rocks shows that there was relatively little modification during the Pleistocene glacial periods. Such a pattern supports recent work which suggests that ice moved through the Wash gap and then fanned out from the Fenland area, rather than entering the region from the north.
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Iheaturu, T. C., R. U. Ideozu, S. Abrakasa e A. E. Jones. "Sequence stratigraphy and tectonic framework of the Gabo Field, Niger Delta, Nigeria". Scientia Africana 21, n.º 3 (29 de janeiro de 2023): 19–36. http://dx.doi.org/10.4314/sa.v21i3.2.
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This research examines the sequence stratigraphic and structural framework of the Gabo Field Niger Delta, Nigeria. Materials used in this research include 3D seismic volume in Seg-Y, ditch cuttings and wells logs. The methods applied are standard methods in addition to using the Frazier and Galloway approach for genetic sequences. The tectonic framework was interpreted in terms of deformational, depositional and post-depositional structures. The deformational structures are faults F1 and F2 – which are closely spaced normal faults and F3 is a syn-depositional growth fault. The depositional structures are pinchouts and interbedded sand/shale sequences whereas the postdepositional structures are compaction and smearing or flexure of the shales. The well correlation shows the sequences are cyclic and the facies analysis of T4 – T9 sands are very fine to medium grained, light to dark brown, texturally mature and moderate to well sorted. The facies associations are fluvial distributary channel, tide dominated fluvial channels, abandoned channel or switching and flood plain deposits. While the depositional environments are upper delta plain, lower delta plain and delta front. Sequence stratigraphic analysis explained the observed increase in shale thickness in the intermediate sections and showed sediment deposition occurred in three (3) systems tracts- Lowstand Systems Tract (LST), the Transgressive Systems Tract (TST) and Highstand Systems Tract (HST). The sedimentological model showed the environments of deposition had a tidal influence and ranged from fluvial to estuarine. The findings of this research may be applied to similar deltaic basins around the world in planning of oilfield development. In addition it may correlate cyclic successions and predict facies distributions of similar depositional patterns.
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Evans, James E., Joshua T. Maurer e Christopher S. Holm-Denoma. "Recognition and significance of Upper Devonian fluvial, estuarine, and mixed siliciclastic-carbonate nearshore marine facies in the San Juan Mountains (southwestern Colorado, USA): Multiple incised valleys backfilled by lowstand and transgressive systems tracts". Geosphere 15, n.º 5 (9 de agosto de 2019): 1479–507. http://dx.doi.org/10.1130/ges02085.1.
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Abstract The Upper Devonian Ignacio Formation (as stratigraphically revised) comprises a transgressive, tide-dominated estuarine depositional system in the San Juan Mountains (Colorado, USA). The unit backfills at least three bedrock paleovalleys (10–30 km wide and ≥42 m deep) with a consistent stratigraphy of tidally influenced fluvial, bayhead-delta, central estuarine-basin, mixed tidal-flat, and estuarine-mouth tidal sandbar deposits. Paleovalleys were oriented northwest while longshore transport was to the north. The deposits represent Upper Devonian lowstand and transgressive systems tracts. The overlying Upper Devonian Elbert Formation (upper member) consists of geographically extensive tidal-flat deposits and is interpreted as mixed siliciclastic-carbonate bay-fill facies that represents an early highstand systems tract. Stratigraphic revision of the Ignacio Formation includes reassigning the basal conglomerate to the East Lime Creek Conglomerate, recognizing an unconformity separating these two units, and incorporating strata previously mapped as the McCracken Sandstone Member (Elbert Formation) into the Ignacio Formation. The Ignacio Formation was previously interpreted as Cambrian, but evidence that it is Devonian includes reexamined fossil data and detrital zircon U-Pb geochronology. The Ignacio Formation has a stratigraphic trend of detrital zircon ages shifting from a single ca. 1.7 Ga age peak to bimodal ca. 1.4 Ga and ca. 1.7 Ga age peaks, which represents local source-area unroofing history. Specifically, the upper plate of a Proterozoic thrust system (ca. 1.7 Ga Twilight Gneiss) was eroded prior to exposure of the lower plate (ca. 1.4 Ga Uncompahgre Formation). These results are a significant alternative interpretation of the geologic history of the southern Rocky Mountains.
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Magalhães, A. J. C., C. M. S. Scherer, G. P. Raja Gabaglia, M. B. Bállico e O. Catuneanu. "Unincised fluvial and tide-dominated estuarine systems from the Mesoproterozoic Lower Tombador Formation, Chapada Diamantina basin, Brazil". Journal of South American Earth Sciences 56 (dezembro de 2014): 68–90. http://dx.doi.org/10.1016/j.jsames.2014.07.010.
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Feldman, Howard R., Christopher G. Maples, Allen W. Archer, Ronald R. West e Erik P. Kvale. "An estuarine model for Pennsylvanian Lagerstätten". Paleontological Society Special Publications 6 (1992): 95. http://dx.doi.org/10.1017/s2475262200006559.
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Estuaries were important sites of deposition throughout most of the Pennsylvanian in the Midcontinent. Modern estuaries typically occur within flooded river valleys where marine and fresh waters mix. Characteristic estuarine circulation results in locally high rates of deposition of muddy sediment that can lead to good preservation of fossils. Several Pennsylvanian conservat-Lagerstätten are best interpreted as having formed within ancient estuaries. Three types of estuarine deposits have been identified. Type 1 estuarine systems are large-scale transgressive systems that start with fluvial sands overlying an erosional surface. This is overlain successively by middle-estuarine laminated mudstone, and finally marine mudstone and shale. Well-preserved fossils occur in laminated mudstones and siltstones. This sequence may include within in it type 3 estuarine Lagerstätten. An example is the Douglas Group (Missourian, Kansas).Type 2 estuarine Lagerstätten consist of thin estuarine deposits confined to narrow paleochannels. This includes the Garnett (Missourian, Kansas) and Hamilton (Virgilian, Kansas) deposits, both of which contain articulated vertebrates and well-preserved plants. Both channels are filled with mixed siliciclastic and carbonate sediments. Fine grained facies from which the best fossils are recovered in both contain evidence of tidal deposition, although tidal rhythmicity is best developed in the Hamilton channel. Plant assemblages in both are dominated by the conifer Walchia, probably indicating a relatively dry climate.Type 3 estuarine Lagerstätten consist of thick gray-shale wedges that overlie coals. The best-known example is the Francis Creek Shale (Desmoinesian, Illinois). A relatively wet climate is indicated by abundant fern and seed-fern foliage. Laminations in shale facies commonly show well-developed tidal rhythmicity. A typical stratigraphic succession starts with laminated shale overlying coal. This grades upwards into flaser and lenticular bedding to ripple and then large-scale cross-bedded sandstone. Upright trees rooted in the coal indicate rapid burial. Well-preserved fossils are recovered from early-diagenetic siderite concretions from the laminated shale.Preservation of fossils is best in laminated mudstones deposited in middle-estuarine environments where conditions are ideal for good preservation. In all cases so far studied the zones of best preservation are well laminated and have sparse (if any) burrows and sessile benthic fossils. Most of the well-preserved organisms are terrestrial, nektonic, or at least mobile. Brackish and fluctuating salinities restricted scavenging and burrowing organisms that may scatter skeletons. High turbidity and deposition rate may have further discouraged many organisms. Matching bedding rhythmicity with tidal cycles allows calculation of depositional rates of 1 cm or more of compacted sediment per 2-week neap-spring tidal cycle. This is consistent with the high rates of deposition known from modern tidal environments. High depositional rates assured that any organism that fell to the sea floor was buried in a few hours to a few days. Once buried anoxic conditions established around decaying carcasses may have led to early mineralization.
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Scoullos, Michael, Fotini Botsou e Christina Zeri. "Linking Environmental Magnetism to Geochemical Studies and Management of Trace Metals. Examples from Fluvial, Estuarine and Marine Systems". Minerals 4, n.º 3 (23 de julho de 2014): 716–45. http://dx.doi.org/10.3390/min4030716.
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Lawler, D. M. "The importance of high-resolution monitoring in erosion and deposition dynamics studies: examples from estuarine and fluvial systems". Geomorphology 64, n.º 1-2 (janeiro de 2005): 1–23. http://dx.doi.org/10.1016/j.geomorph.2004.04.005.
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Buatois, Luis A., Gabriela Mángano e Timothy R. Carr. "Sedimentology and Ichnology of Paleozoic Estuarine and Shoreface Reservoirs, Morrow Sandstone, Lower Pennsylvanian of Southwest Kansas, USA". Bulletin (Kansas Geological Survey), n.º 243 (1 de janeiro de 1999): 1–35. https://doi.org/10.17161/kgsbulletin.no.243.20399.
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Integration of ichnologic, sedimentologic, and stratigraphic studies of cores from Lower Pennsylvanian oil and gas reservoirs (lower Morrow Sandstone, southwest Kansas) allows researchers to distinguish between estuarine- and open-marine deposits. This study represents one of the first published ichnologic analyses of a Paleozoic reservoir and, therefore, provides a unique opportunity to test the applicability of models based on observations from Mesozoic and Cenozoic reservoirs. Fifteen facies grouped in two facies-assemblages (estuarine and open-marine) were recognized from the lower Morrow. The estuarine facies-assemblage includes both interfluve and valley-fill deposits, encompassing a variety of depositional environments, such as fluvial channels, interfluve paleosols, upper-estuarine channels, estuary bay, restricted tidal flats, tidal channels, and estuary mouth. The presence of a low-diversity, opportunistic, impoverished-marine ichnofauna dominated by infaunal structures, which represents a mixed Skolithos and depauperate Cruziana ichnofacies, supports a brackish-water setting. Overall distribution of ichnofossils along the estuarine valley was mainly controlled by the salinity gradient, with other parameters, such as oxygenation, substrate and energy, acting at a more local scale. The lower Morrow estuarine system displays the classical tripartite division (seaward marine sand plug, fine-grained central bay, and sandy landward zone) of wave-dominated estuaries, with local evidence of tidal action. The estuarine valley displays a northwest-southeast trend, draining to the open sea towards the southeast. A major lowstand of sea level at the Mississippian-Pennsylvanian boundary is thought to be responsible for incision of the estuarine valley. The open-marine facies assemblage includes upper-shoreface, middle-shoreface, lower-shoreface, offshore-transition, offshore, and shelf deposits. In contrast to the estuarine assemblage, open-marine ichnofaunas are characterized by highly diverse biogenic structures produced by a benthic fauna developed under conditions of normal salinity. Trace-fossil and facies analyses allow environmental subdivision of the shoreface and offshore packages and suggest deposition in a weakly storm-affected nearshore area. An onshore-offshore replacement of the Skolithos ichnofacies by the Cruziana ichnofacies is clearly displayed. Identification of incised valley systems in the lower Morrow has implications for hydrocarbon exploration and subsequent production because reservoir quality is largely determined by facies distribution and external geometry. While the open-marine model predicts a layer-cake style of facies distribution as a consequence of strandline-shoreline progradation, recognition of valley-fill sequences points to more compartmentalized reservoirs, due to heterogeneity created at different scales by valley incision and distribution of facies and facies assemblages. The emergent picture is one of a heterogeneous and compartmentalized reservoir, displaying high variability in sedimentary facies and a complex pattern in distribution and connectivity of reservoir sandstones.
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Al-Masgari, Abd Al-Salam, Mohamed Elsaadany, Numair A. Siddiqui, Abdul Halim Abdul Latiff, Azli Abu Bakar, Sami Elkurdy, Maman Hermana, Ismailalwali Babikir, Qazi Sohail Imran e Teslim Adeleke. "Geomorphological Geometries and High-Resolution Seismic Sequence Stratigraphy of Malay Basin’s Fluvial Succession". Applied Sciences 11, n.º 11 (2 de junho de 2021): 5156. http://dx.doi.org/10.3390/app11115156.
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This study identified the Pleistocene depositional succession of the group (A) (marine, estuarine, and fluvial depositional systems) of the Melor and Inas fields in the central Malay Basin from the seafloor to approximately −507 ms (522 m). During the last few years, hydrocarbon exploration in Malay Basin has moved to focus on stratigraphic traps, specifically those that existed with channel sands. These traps motivate carrying out this research to image and locate these kinds of traps. It can be difficult to determine if closely spaced-out channels and channel belts exist within several seismic sequences in map-view with proper seismic sequence geomorphic elements and stratigraphic surfaces seismic cross lines, or probably reinforce the auto-cyclic aggregational stacking of the avulsing rivers precisely. This analysis overcomes this challenge by combining well-log with three-dimensional (3D) seismic data to resolve the deposition stratigraphic discontinuities’ considerable resolution. Three-dimensional (3D) seismic volume and high-resolution two-dimensional (2D) seismic sections with several wells were utilized. A high-resolution seismic sequence stratigraphy framework of three main seismic sequences (3rd order), four Parasequences sets (4th order), and seven Parasequences (5th order) have been established. The time slice images at consecutive two-way times display single meandering channels ranging in width from 170 to 900 m. Moreover, other geomorphological elements have been perfectly imaged, elements such as interfluves, incised valleys, chute cutoff, point bars, and extinction surfaces, providing proof of rapid growth and transformation of deposits. The high-resolution 2D sections with Cosine of Phase seismic attributes have facilitated identifying the reflection terminations against the stratigraphic amplitude. Several continuous and discontinuous channels, fluvial point bars, and marine sediments through the sequence stratigraphic framework have been addressed. The whole series reveals that almost all fluvial systems lay in the valleys at each depositional sequence’s bottom bars. The degradational stacking patterns are characterized by the fluvial channels with no evidence of fluvial aggradation. Moreover, the aggradation stage is restricted to marine sedimentation incursions. The 3D description of these deposits permits distinguishing seismic facies of the abandoned mud channel and the sand point bar deposits. The continuous meandering channel, which is filled by muddy deposits, may function as horizontal muddy barriers or baffles that might isolate the reservoir body into separate storage containers. The 3rd, 4th, and 5th orders of the seismic sequences were established for the studied succession. The essential geomorphological elements have been imaged utilizing several seismic attributes.
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Stone, Jeffery R. "Using Diatoms as Ecological and Paleoecological Indicators in Riverine Environments". Paleontological Society Papers 13 (outubro de 2007): 121–30. http://dx.doi.org/10.1017/s1089332600001492.
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Fossil diatom assemblages are useful for reconstructing past environmental changes in riverine systems. However, few studies have attempted to utilize paleolimnological techniques in these settings. Analysis of sediments from riverine environments can provide key information predating the impact of human development, which cannot be acquired by other means. Paleolimnological techniques can be used to determine the natural variability in these systems and to estimate the magnitude and rates of change that the environment may have undergone as a result of anthropogenic or climatic factors, and to provide realistic goals for management of negatively-impacted systems.Reconstructing past riverine settings requires an understanding of the factors that control the spatial distribution of diatoms in riverine settings; this paper discusses the impact of resources, stressors, and disturbance events, which are the primary controls on the distribution of benthic diatoms in modern riverine environments. A selection of case studies that utilize paleolimnological techniques to infer past stream hydrology are also discussed; these examples encompass the use of fossil diatom assemblages from sediments recovered from lowland floodplain and meandering river systems, estuarine environments, fluvial lakes, arctic deltaic environments, and terminal lakes.
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Oliveira, Vítor H., Magda C. Sousa, Fernando Morgado e João M. Dias. "Modeling the Impact of Extreme River Discharge on the Nutrient Dynamics and Dissolved Oxygen in Two Adjacent Estuaries (Portugal)". Journal of Marine Science and Engineering 7, n.º 11 (13 de novembro de 2019): 412. http://dx.doi.org/10.3390/jmse7110412.
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The Minho and Lima are adjacent estuaries located in the north of Portugal, with high ecological and economic importance. To address gaps in knowledge about changes in nutrient patterns in adjacent estuaries subject to different freshwater inflows, a numerical model, Delft3D, was implemented and developed, using a single domain, which allowed physical communication between estuaries. Calibration and validation of the model was successfully performed. Three numerical simulations were carried out, in which only river flows were varied (1st corresponds to a baseline numerical run, the 2nd a flood scenario, and the 3rd a drought scenario). Under flooding conditions, similar patterns were verified in both estuaries, with high fluvial discharges showing to have a reduced impact on both estuarine dynamics. In this case the nutrients were not a limiting factor for the biota, both for summer and winter seasons, since there was no significant decrease in dissolved oxygen concentration. For the drought scenario, it was observed that the estuary with the lower inflow of freshwater (Lima) was the most affected, with a significant decrease in the concentration of nutrients and oxygen dissolved in the winter season (decrease of 2 mg O2/L). In conclusion, this work reveals that it is essential to continuously monitor dam-controlled estuarine systems, as a significant decrease in river discharge will cause significant changes in the variables analysed (O2, PO4, and NO3) and may cause loss of biodiversity.
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Perignon, Mariela, Jordan Adams, Irina Overeem e Paola Passalacqua. "Dominant process zones in a mixed fluvial–tidal delta are morphologically distinct". Earth Surface Dynamics 8, n.º 3 (25 de setembro de 2020): 809–24. http://dx.doi.org/10.5194/esurf-8-809-2020.
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Abstract. The morphology of deltas is determined by the spatial extent and variability of the geomorphic processes that shape them. While in some cases resilient, deltas are increasingly threatened by natural and anthropogenic forces, such as sea level rise and land use change, which can drastically alter the rates and patterns of sediment transport. Quantifying process patterns can improve our predictive understanding of how different zones within delta systems will respond to future change. Available remotely sensed imagery can help, but appropriate tools are needed for pattern extraction and analysis. We present a method for extracting information about the nature and spatial extent of active geomorphic processes across deltas with 10 parameters quantifying the geometry of each of 1239 islands and the channels around them using machine learning. The method consists of a two-step unsupervised machine learning algorithm that clusters islands into spatially continuous zones based on the 10 morphological metrics extracted from remotely sensed imagery. By applying this method to the Ganges–Brahmaputra–Meghna Delta, we find that the system can be divided into six major zones. Classification results show that active fluvial island construction and bar migration processes are limited to relatively narrow zones along the main Ganges River and Brahmaputra and Meghna corridors, whereas zones in the mature upper delta plain with smaller fluvial distributary channels stand out as their own morphometric class. The classification also shows good correspondence with known gradients in the influence of tidal energy with distinct classes for islands in the backwater zone and in the purely tidally controlled region of the delta. Islands at the delta front under the mixed influence of tides, fluvial–estuarine construction, and local wave reworking have their own characteristic shape and channel configuration. The method is not able to distinguish between islands with embankments (polders) and natural islands in the nearby mangrove forest (Sundarbans), suggesting that human modifications have not yet altered the gross geometry of the islands beyond their previous “natural” morphology or that the input data (time, resolution) used in this study are preventing the identification of a human signature. These results demonstrate that machine learning and remotely sensed imagery are useful tools for identifying the spatial patterns of geomorphic processes across delta systems.
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Hess, Aaron M., e Christopher R. Fielding. "Analysis of coastal-plain fluvial architecture and high-frequency stacking patterns in the Upper Cretaceous Masuk Formation, Utah, U.S.A.: Climate-driven cyclicity?" Journal of Sedimentary Research 90, n.º 10 (1 de outubro de 2020): 1265–85. http://dx.doi.org/10.2110/jsr.2020.63.
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ABSTRACT Most sequence stratigraphic models are based on the premise that relative changes in sea level (RSL) control stacking patterns in continental-margin settings. An alternative hypothesis, however, is that upstream factors, notably variations in relative water discharge (RQW) or the ratio of water to sediment discharge can influence or control stratal stacking patterns in fluvial systems. Sequence boundaries of RQW-driven systems differ from those driven by base-level fluctuations in that: 1) the depth of incision increases updip, and 2) rates of erosion are spatially uniform, leading to the formation of widespread, planar sequence boundaries. This paper presents an architectural and stratigraphic analysis of the well-exposed Masuk Formation of the Henry Mountains Syncline in southern Utah, an Upper Cretaceous coastal-plain fluvial succession that is interpreted to have been influenced significantly by RQW. Six lithofacies are recognized, three (Facies 1–3) recording floodbasin, mire, and (in one short interval) estuarine environments, and three (Facies 4–6) record different kinds of channel fills on a coastal alluvial plain. Seven major composite channel bodies (Facies 4–6), separated by intervals of non-channel deposits (Facies 1–3), are recognized in the stratigraphic interval. Composite channel bodies display planar, sheet-like geometry and are laterally continuous to a significantly greater extent (> 10 km) than would be expected from purely autogenic channel-belt construction. Together, these intervals record a series of high-frequency sequences, formed along the western margin of the Western Interior Seaway. In each individual sequence is a repetitive facies succession from a basal chaotic sandstone with admixed mudrock and sandstone transitioning upward to a more organized cross-bedded and stratified sandstone. This is interpreted to record cyclical changes from a peaked (flashy) discharge regime to a more normal runoff regime. Paleoflow data indicate a dominance of transverse (eastward-directed) dispersal early in the accumulation of the Masuk Formation, shifting to a pattern of greater axial (northward) dispersal over time. The RQW signal is strong in the lower part of the formation, decreasing upward. This suggests that the relatively short-headed streams draining from the rising Sevier fold–thrust belt were strongly influenced by climatic cyclicity, whereas more distally sourced systems were not. This study provides new insights into the architecture and stacking patterns of coastal-plain fluvial successions, emphasizing the plausible role that climate can play in shaping alluvial architecture in the rock record.
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Bayona, German, Carlos Jaramillo, Milton Rueda, Andrés Reyes Harker e Vladimir Torres. "PALEOCENE-MIDDLE MIOCENE FLEXURAL-MARGIN MIGRATION OF THE NONMARINE LLANOS FORELAND BASIN OF COLOMBIA". CT&F - Ciencia, Tecnología y Futuro 3, n.º 3 (31 de dezembro de 2007): 51–70. http://dx.doi.org/10.29047/01225383.475.
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A foreland basin is a dynamic system whose depositional systems migrate in response to changes in tectonic uplift patterns, sedimentary filling processes and isostatic rebound of the lithosphere. The Paleocene-middle Miocene foreland system of the Llanos foothills and Llanos basin of Colombia includes regional unconformities, abrupt changes in lithology/stacking patterns and flooding surfaces bounding reservoir and seal units. Here we integrate a systematic biostratigraphic study, stratal architecture and tectonic subsidence analyses, regional seismic profiles, and provenance data to define the diachronism of such surfaces and to document the direction of migration of foreland depozones. In a flexurally-deformed basin, sandstone composition, rates of accommodation and sediment supply vary across and along the basin. We show how a coeval depositional profile in the Llanos foothills-Llanos foreland basin consists of litharenites interbedded with mudstones (seal rock, supplied from the orogenic front to the west) that correlate cratonward with organic-rich mudstones and coal (source rock), and to amalgamated fluvial-estuarine quartzarenites (reservoir rock, supplied from the craton to the east) adjacent to a subaerial forebulge (unconformity). This system migrated northward and eastward during the Paleocene, westward during the early-middle Eocene, and eastward during the Oligocene. In the lower-middle Miocene succession of the Llanos basin, identification of flooding events indicates a westward encroaching of a shallow-water lacustrine system that covered an eastward-directed fluvial-deltaic system. A similar process has been documented in other basins in Venezuela and Bolivia, indicating the regional extent of such flooding event may be related to the onset of Andean-scale mountain-building processes.
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Patey, Géraldine, Catherine M. Couillard, Hilaire Drouineau, Guy Verreault, Fabien Pierron, Patrick Lambert, Magalie Baudrimont e Patrice Couture. "Early back-calculated size-at-age of Atlantic yellow eels sampled along ecological gradients in the Gironde and St. Lawrence hydrographical systems". Canadian Journal of Fisheries and Aquatic Sciences 75, n.º 8 (agosto de 2018): 1270–79. http://dx.doi.org/10.1139/cjfas-2017-0025.
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An international sampling program investigating the causes of the decline of American eels (Anguilla rostrata) and European eels (Anguilla anguilla) in the St. Lawrence (Canada) and Gironde (France) rivers systems provided the opportunity to compare early growth of eels of each species among habitats using back-calculated size-at-age from 1 to 5 years old. Our study supports previous studies showing that the early back-calculated lengths of A. anguilla were higher in downstream and more saline Gironde system habitats than in the upstream fluvial section and provides a new indication that length at 1 year old is twice higher than that reported 10 years earlier. However, our data contradict the current paradigm for A. rostrata by providing evidence that early size-at-age of eels from the upstream St. Lawrence system, most distant from the spawning area, exceeds those of eels sampled downstream, at less distant sites in the estuarine section. Overall, these observations are consistent with the hypothesis that the observed spatial variations in early growth rate of yellow eels sampled in the St. Lawrence and Gironde systems are the consequence of processes occurring in the first year of age, such as genetic selection and (or) genetically dependent habitat choice.
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Proust, Jean-Noel, David Menier, Francois Guillocheau, Pol Guennoc, Stephane Bonnet, Delphine Rouby e C. Le Corre. "Les vallees fossiles de la baie de la Vilaine; nature et evolution du prisme sedimentaire cotier du Pleistocene armoricain". Bulletin de la Société Géologique de France 172, n.º 6 (1 de novembro de 2001): 737–49. http://dx.doi.org/10.2113/172.6.737.
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Abstract The study of a dense network of high resolution seismic profiles in the bay of Vilaine, INSU-CNRS cruise Geovill, have led to the characterization of the architecture of the sediment wedge preserved between the coast and the 50 m isobath. This wedge lies on a substratum composed of three seismic units, U1, U2 and U3 respectively attributed to metamorphic and magmatic rocks, Lutetian and Ypresian sandy carbonates and post-Eocene sediments. The coastal sediment wedge comprises three major units. A basal unit (U4), dated around 600 to 300 ky BP, interpreted as braided river sandy conglomerates. A median unit (U5) corresponding to estuarine and fluvial sandstones and clays that give way to the west to mouth bar sandstones. A sommital unit (U6) attributed to marine argillites and barrier island sandstones dated from 8110+ or -200 years at the base. These three units are bounded by two major surfaces: an unconformity between U4 and U5 and a marine (wave and tidal) ravinement surface between U5 and U6. The unconformity is interpreted as a sequence boundary between two depositional sequences: a lower one with U4 seismic unit and a topmost one with U5 and U6 seismic units. Based on the available datations, the lower sequence is attributed to the Saalian and/or Elsterian glacial cycles and, the upper sequence to the Weichselian (lowstand systems tract) and to the Holocene marine transgression (transgressive systems tract). The passage from one sequence to the other corresponds however to a drastic shift in the paleoflow directions (60 degrees ) in the Bay of Vilaine closely related to the main faults orientations. The tectonic activity in Brittany during the Pleistocene, linked to intraplate stress, seems to exert a control on sediment architecture in the coastal wedge. Indeed, the tilt of the Armorican Massif during that period has caused a complete rejuvenation of the fluvial profiles in land and the separation of the paleo-Vilaine from the Paleo-Loire river courses.
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Huggett, Rebecca D., Duncan A. Purdie e Ivan D. Haigh. "Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries". Estuaries and Coasts 44, n.º 1 (1 de julho de 2020): 54–69. http://dx.doi.org/10.1007/s12237-020-00776-3.
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AbstractSimple flushing time calculations for estuarine systems can be used as proxies for eutrophication susceptibility. However, more complex methods are required to better understand entire systems. Understanding of the hydrodynamics driving circulation and flushing times in small, eutrophic, temperate estuaries is less advanced than larger counterparts due to lack of data and difficulties in accurately modelling small-scale systems. This paper uses the microtidal Christchurch Harbour estuary in Southern UK as a case study to elucidate the physical controls on eutrophication susceptibility in small shallow basins. A depth-averaged hydrodynamic model has been configured of the estuary to investigate the physical processes driving circulation with particular emphasis on understanding the impact of riverine inputs to this system. Results indicate circulation control changes from tidally to fluvially driven as riverine inputs increase. Flushing times, calculated using a particle tracking method, indicate that the system can take as long as 132 h to flush when river flow is low, or as short as 12 h when riverine input is exceptionally high. When total river flow into the estuary is less than 30 m3 s−1, tidal flux is the dominant hydrodynamic control, which results in high flushing times during neap tides. Conversely, when riverine input is greater than 30 m3 s−1, the dominant hydrodynamic control is fluvial flux, and flushing times during spring tides are longer than at neaps. The methodology presented here shows that modelling at small spatial scales is possible but highlights the importance of particle tracking methods to determine flushing time variability across a system.
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Opekunova, Marina Y., Natalia V. Kichigina, Artem A. Rybchenko e Anton V. Silaev. "Channel Deformations and Hazardous Processes of the Left-Bank Tributaries of The Angara River (Eastern Siberia)". Water 15, n.º 2 (10 de janeiro de 2023): 291. http://dx.doi.org/10.3390/w15020291.
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The influence of anthropogenic and natural factors in the trends and mechanisms of development at various topological levels is determined based on relevant information on the structure and dynamics of fluvial systems in the south of Eastern Siberia in various geodynamic settings. This article considers the current spatial and temporal dynamics of the hydrological conditions of the vast territory of the Angara River and its influence on channel deformations and the manifestation of dangerous processes. An analysis of fluctuations in the maximum runoff using differential integral curves resulted in the identification of six periods of water content according to the maximum annual discharges for the period spanning from the beginning of observations to 2020 for the rivers under consideration. The dynamics and intensity of manifestation of hydrological and geological hazardous processes are demonstrated using a series of studies conducted under various geodynamic conditions. Catastrophic floods brought on by enhanced cyclonic activity are accompanied by the destruction of the bank. The highest rate of bank erosion in the plains is 1.5 to 2 m per year, and for rivers in mountains and piedmonts it is 2 to 6 m per year. An analysis of the dynamics of the development of floodplain–channel complexes in the Upper Angara region makes it possible to distinguish two zones of actively developing floodplain–channel complexes: piedmont and estuarine, separated by a relatively stable plain zone.
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Antunes do Carmo, J. S. "Environmental impacts of human action in watercourses". Natural Hazards and Earth System Sciences Discussions 2, n.º 10 (14 de outubro de 2014): 6499–530. http://dx.doi.org/10.5194/nhessd-2-6499-2014.
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Abstract. The economic, social and environmental conditions of various European river basins and estuarine systems have changed dramatically in the last decades as a consequence of anthropogenic effects, and they will go on changing in the years to come due to increasing human pressure. Particularly in Portugal, various river-estuary systems have undergone several human interventions, notably engineering works to restore considerable stretches of channels and river banks. Whenever the characteristics and natural evolution of a river are altered as a result of human intervention there is an environmental impact. In other words, it is understood that differences can be observed between any present situation that is the result of the evolution of an environment after human intervention, and the natural situation that would have existed if this type of intervention had not taken place, taking into account our previous knowledge of the situation. A thorough understanding of the fluvial processes and new strategies are needed to develop a multifunctional use structure, which must take into account the many-faceted aims of sustainable development. This paper provides a brief description of the nature and distribution of the direct and indirect types of impact arising out of building and operating large dams, as well as some specific points that should be taken into consideration. It also reflects on the way in which the problem of extracting inert material from water environments has been dealt with in Portugal and offers a brief technical contribution which, although qualitative, provides a basic record and explanation of the consequences of significant interventions in water environments that have not been properly assessed or have not taken other mitigating circumstances into consideration.
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Andreou, D., C. M. Antognazza, C. F. Williams, H. Bradley, A. J. Reading, E. A. Hardouin, J. R. Stewart et al. "Vicariance in a generalist fish parasite driven by climate and salinity tolerance of hosts". Parasitology 147, n.º 14 (10 de setembro de 2020): 1658–64. http://dx.doi.org/10.1017/s0031182020001663.
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AbstractAcanthocephalans are parasites with complex lifecycles that are important components of aquatic systems and are often model species for parasite-mediated host manipulation. Genetic characterization has recently resurrected Pomphorhynchus tereticollis as a distinct species from Pomphorhynchus laevis, with potential implications for fisheries management and host manipulation research. Morphological and molecular examinations of parasites from 7 English rivers across 9 fish species revealed that P. tereticollis was the only Pomphorhynchus parasite present in Britain, rather than P. laevis as previously recorded. Molecular analyses included two non-overlapping regions of the mitochondrial gene – cytochrome oxidase and generated 62 sequences for the shorter fragment (295 bp) and 74 for the larger fragment (583 bp). These were combined with 61 and 13 sequences respectively, from Genbank. A phylogenetic analysis using the two genetic regions and all the DNA sequences available for P. tereticollis identified two distinct genetic lineages in Britain. One lineage, possibly associated with cold water tolerant fish, potentially spread to the northern parts of Britain from the Baltic region via a northern route across the estuarine area of what is now the North Sea during the last Glaciation. The other lineage, associated with temperate freshwater fish, may have arrived later via the Rhine/Thames fluvial connection during the last glaciation or early Holocene when sea levels were low. These results raise important questions on this generalist parasite and its variously environmentally adapted hosts, and especially in relation to the consequences for parasite vicariance.
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Aouiche, Ismail, Mouncef Sedrati e Edward J. Anthony. "Modelling of Sediment Transport and Deposition in Generating River-Mouth Closure: Oum-Errabia River, Morocco". Journal of Marine Science and Engineering 11, n.º 11 (26 de outubro de 2023): 2051. http://dx.doi.org/10.3390/jmse11112051.
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River mouths are dynamic systems that can respond rapidly to both fluxes in fluvial water and sediment discharge and marine energy conditions, notably waves. On semi-arid wave-exposed coasts, the morphosedimentary behaviour of river mouths is particularly sensitive to variations in water discharge, which can be significantly influenced by climate variations, in addition to anthropogenic actions such as the construction of dams for water resource needs. In this climatic setting, an increasingly common consequence of decreasing river water discharge is the more or less prolonged closure of river mouths. Most studies have addressed river-mouth closure using analytical, parametric, numerical, or statistical models. The present study uses output from four numerical models to elucidate the hydrodynamic and sedimentary behaviour of the mouth of the Oum-Errabia River (catchment size: 35,000 km2), which debouches on the Atlantic coast of Morocco. The historical evolution of the river mouth and the impact of human interventions, such as the construction of dams, are discussed. The study also briefly discusses the impact of the recent closure of the river outlet, in response to particularly low water discharge, on the marine ecosystem and water quality. The modelling results covering a one-year simulation in this situation of closure indicate a deposition of 427,400 m3 of sediment in front of the mouth of the Oum-Errabia. Ensuring permanent river-mouth opening and tidal flushing and renewal of this river’s estuarine waters will necessitate costly regular dredging.
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Leal, Renato Amabile, Eduardo Guimarães Barboza, Mauro Michelena Andrade e Volney Júnior Borges Bitencourt. "Conditioning Factors in the Formation of the Inverted Intra-lagoon Delta of the Urussanga Velha Lagoon, Southern Santa Catarina, Brazil". Pesquisas em Geociências 50, n.º 3 (29 de agosto de 2023): e133807. http://dx.doi.org/10.22456/1807-9806.133807.
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The Southern Santa Catarina Coastal Plain is formed by the overlapping of sedimentary deposits of two lagoon/barrier depositional systems. One of the lagoons of the most recent system (holocenic) presents an intra-lagoon delta of peculiar morphology. This delta is formed from the ocean into the lagoon. The present study aimed to identify which are the factors responsible for the formation and evolution of this morphological feature. To identify the conditioning factors involved, a spatiotemporal analysis was conducted between 1957 and 2012. Remote sensing data was used to identify hydrodynamic patterns. This data was analyzed together with water parameters (turbidity and salinity) and relative sea level. The correlation between this information and climatological data (low and very low-frequency climate variabilities) was also integrated. The main conditioning factors identified included: phase changes of the Pacific Decadal Oscillation (PDO) and of the El Niño - Southern Oscillation (ENSO); the influence of positive low-frequency sea-level oscillations (storm surge); and human interference. Both climate variability modes were associated with a high occurrence of rainfall in the region, which consequently provided a high availability of sediments in the Urussanga River fluvial-estuarine system. In addition to influencing rainfall increase, periods, when El Niño predominated, tended to result in a high occurrence of positive storm surges, which influenced the hydrodynamic flow responsible for transporting sediment towards the lagoon’s interior and, consequently, for forming the delta.
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Astini, Ricardo A., e Larisa F. Marengo. "Paleoenvironments and sequential stratigraphy of Ordovician marginal marine deposits of Sierra de Zapla (Sierras Subandinas, northwestern Argentina) and their relation with the Central Andean Basin". Andean Geology 33, n.º 2 (30 de junho de 2010): 247. http://dx.doi.org/10.5027/andgeov33n2-a03.
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The best and most complete palynologically constrained Ordovician section across the Sierras Subandinas crops out in the southern part of the Sierra de Zapla along the Capillas River (Subandean Ranges, Jujuy Province). The dominantly marginal marine setting explains the scarcity of invertebrates throughout the section. Palynomorphs are the main tool in stratigraphic studies of the area and trace fossils are important aids in paleoenvironmental analysis. Based on a detailed facies analysis, geometry and paleocurrent analysis, and recognition of key surfaces, four depositional sequences (S1-S4) with different internal arrangements and compatible with 3rd order cycles were identified. The Zanjón Formation (upper part of Global Stage 2 and Global Stage 3) with unexposed base, initiates the stratigraphic section and it is characterized by a heterolithic facies association with subordinate storm layers, thin-bedded phosphate-rich micro-conglomerates and inarticulate-rich shell beds. Common subaerial exposure features like truncated ripple tops and mud cracks suggest tidal flat environments. This interval yields a mixed Skolithos-Cruziana ichnofacies. Towards the top, an increase in mottling and a gradual change into dominant purplish-red colors (Laja Morada Member of the Labrado Formation) indicate a protracted subaerial emergence during a Darriwilian (Global Stage 4) relative sea-level drop, and a fluctuating water table in interfluves. This unit is covered in sharp erosive boundary by the Lagunilla Member of the Labrado Formation, suggesting development of composite fluvial incisions. Sandy fluvial to tide-dominated estuarine fills and thoroughly-bioturbated subtidal hetherolithic beds overlie the sequence boundary representing a typical transgressive systems tract. Development of surfaces with dominant Skolithos forms are interpreted as representing Glossifungites ichnofacies typically indicating by-pass erosion and firm-ground development previous to reworking of interfluves by advancing ravinement surface. The Capillas Formation (upper Darriwilian and lower part of Global Stage 5), sharply levels the previous estuarine complexes and represents a fine-grained wedge that gradually coarsens up. This unit contains the only truly marine shelly fauna concentrated in few storm beds above the fine-grained interval that characterizes a maximum flooding stage. This is the only interval that can be positively correlated with sections in the Cordillera Oriental to the west and Bolivia. A gradual coarsening to silty sandstones and the replacement of Cruziana by Skolithos dominated ichnofacies suggest a shallowing-upward section, capped by the thick-bedded, high energy quartz sandstones with pipe-rock structures of the Centinela Formation (middle and upper part of Global Stage 5). A shallowing-upward trend indicates the progradation of deltaic complexes, which in turn were erosively truncated by the waxing stage of the Gondwanan Hirnantian (uppermost Ordovician) ice-cap represented by the Zapla Formation (Global Stage 6) along the Central Andes. Above the diamictite-rich Zapla Formation the Lipeón Formation (Silurian) is interpreted as related to repeated transgressive ravinement surfaces that truncated Fe+2 saturated estuaries after a waning glacial stage and isostatic rebound, favouring the deposition of oolitic ironstones and succeeded by the development of a Zoophycos dominated muddy shelf.
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Algheryafi, Hasan, César Viseras, Camilo Polo e Khalid Al-Ramadan. "Facies architecture and paleogeography evolution of regressive wave-dominated shorelines transitioning into tide-dominated estuaries: Early Devonian Subbat Member, Jauf Formation, Saudi Arabia". Journal of Sedimentary Research 92, n.º 10 (26 de outubro de 2022): 955–87. http://dx.doi.org/10.2110/jsr.2021.112.
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Abstract The Paleozoic succession on the northern Arabian Plate was deposited during several regressive and transgressive events. The Early Devonian Subbat Member of the Jauf Formation comprises several smaller-scale intervals of the Paleozoic succession that were interpreted based on large-scale observations from outcrop and subsurface data. This study utilizes process-based sedimentology and investigates facies stacking, lateral continuity of sand bodies, and ichnofacies to interpret an open marine wave-dominated forced regressive system, that is followed by transgressive shorelines. This study integrates a total of 417 meters of the Devonian stratigraphy from four outcrops and two shallow cores. This dataset records a third-order sequence which developed through an extensive intra-plate siliciclastic influx in between two carbonate units during the deposition of the Subbat Member. This study illustrates the evolution of a falling-stage systems tract that is characterized by shoreface sand bodies and an erosional-based delta front in the lower Subbat Member. These sediments overlie a regressive surface of marine erosion (RSME), extending for hundreds of kilometers and transitioning to an overall transgression in the upper parts of the Subbat Member. This study interprets a total of seven facies associations (FAs): i) offshore, ii) wave-dominated delta, iii) shoreface to offshore transition, iv) fluvial channels, v) crevasse splays, vi) paleosol, and vii) estuarine facies associations. In the lower part of the Subbat Member, the wave-dominated delta and shoreface to offshore transitional FAs overlie the marine shelf strata of the offshore FA and develop a RSME. Fluvial channels and crevasse splays FAs are interpreted. Unique assemblages of trace fossils, in terms of intensity and diversity, ranging from the Nereites Ichnofacies to Skolithos Ichnofacies, play a major role in the understanding of the overall water depth and depositional setting. Distinctive terrestrial Prototaxites fossils are present in sheet-like bodies and are interpreted as part of extensive crevasse splays that formed during major river flooding events. This study provides a unique integrated approach using ichnology, sedimentology, and sequence stratigraphy to better understand the spatial and temporal facies distribution of a forced regressive sequence and refine the paleogeography of northern Arabia during Early Devonian time.
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Rogers, James P., e Mark W. Longman. "Reservoir Characterization of the Pennsylvanian (Desmoinesian) Lower Bartlesville Sandstone in Big Sandy and Clinesmith Fields, Southeast Kansas". Mountain Geologist 56, n.º 2 (1 de maio de 2019): 185–226. http://dx.doi.org/10.31582/rmag.mg.56.2.185.
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Big Sandy and Clinesmith oil fields are located about five miles apart along the boundary between Woodson and Wilson counties in southeast Kansas. They are located on the Pennsylvanian Cherokee Platform and were discovered almost 60 years apart in 1923 and 1982 respectively. Both fields produce from Desmoinesian lower Bartlesville sandstone reservoirs at shallow depths (1,100 to 1,200 ft) from reservoirs that have been interpreted as “shoestring sandstones.” However, if Big Sandy is restricted just to the area of Section 23 and the southeast quarter of Section 22, T26S, R14E where it offers the best wireline log control, the two fields have different orientations. Big Sandy has a southwest/northeast trend almost perpendicular to Clinesmith Field, which trends from north-northwest to southward. Big Sandy Field has a more elliptical shape with a length-to-width ratio of 3:1, vs. 10:1 for the very linear Clinesmith Field. Another major difference between the two fields is that the gamma-ray logs in and along the Clinesmith reservoir trend generally have a fairly well-defined fining-upward trend characteristic of a fluvial channel system. Big Sandy logs, in contrast, show much more variability from well to well. Petrographically the two fields have characteristics that are both consistent and strikingly different. Both reservoirs have a consistent very-fine to fine sand grain size with fair to well-sorted grains. Both also have texturally immature grains that are angular to subrounded with nearly identical compositions of abundant quartz, and associated plagioclase, biotite, muscovite, plant debris, and metamorphic rock fragments. Thus, the Bartlesville Sandstone in both fields had the same nearby sediment source terrain comprised mainly of granites and metamorphic rocks. Each field also produces mainly from primary interparticle porosity in sandstones with loosely packed grains where total porosity locally exceeds 20%. A difference is that, although both fields contain common shale clasts, those in Big Sandy Field tend to be much larger and occur with common siderite (iron carbonate) nodules. Siderite is rare in Clinesmith Field although a few small nodules occur in the associated floodplain shales, along with carbonaceous partings. Also present in Big Sandy’s reservoir are other iron-bearing minerals such as glauconite, pyrite, and chlorite, although all of these are far less common than the siderite. Such an abundance of iron-rich minerals can occur in marginal marine environments such as estuaries where a reducing diagenetic environment forms just below the sediment/water interface. In contrast, well-oxygenated fluvial systems generally contain any iron in highly oxidized forms such as hematite and limonite. From these observations, it appears that Big Sandy’s reservoir interval was deposited in an estuarine (coastal marine) setting with diverse localized depositional environments whereas the Clinesmith reservoir represents a nearly straight, south-flowing fluvial channel and adjacent floodplain, with no marine influence on deposition.
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Prinz, L., A. Schäfer, T. McCann, T. Utescher, P. Lokay e S. Asmus. "Facies analysis and depositional model of the Serravallian-age Neurath Sand, Lower Rhine Basin (W Germany)". Netherlands Journal of Geosciences 96, n.º 3 (23 de janeiro de 2017): 211–31. http://dx.doi.org/10.1017/njg.2016.51.
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AbstractThe up to 60 m thick Neurath Sand (Serravallian, late middle Miocene) is one of several marine sands in the Lower Rhine Basin which were deposited as a result of North Sea transgressive activity in Cenozoic times. The shallow-marine Neurath Sand is well exposed in the Garzweiler open-cast mine, which is located in the centre of the Lower Rhine Basin. Detailed examination of three sediment profiles extending from the underlying Frimmersdorf Seam via the Neurath Sand and through to the overlying Garzweiler Seam, integrating both sedimentological and palaeontological data, has enabled the depositional setting of the area to be reconstructed.Six subenvironments are recognised in the Neurath Sand, commencing with the upper shoreface (1) sediments characterised by glauconite-rich sands and an extensive biota (Ophiomorphaichnosp.). These are associated with the silt-rich sands of a transitional subenvironment (2), containingSkolithos linearis, Planolitesichnosp. andTeichichnusichnosp. These silt-rich sands grade up to the upper shoreface subenvironment (1), which is indicative of an initial regressive trend. The overlying intertidal deposits can be subdivided into a lower breaker zone (3), characterised by ridge-and-runnel systems, and the swash zone (4) where the surge and backwash of waves resulted in the deposition of high-energy laminites. The intertidal deposits were capped by aeolian backshore sediments (5). Extensive root traces present in this latter subenvironment reflect the development of the overlying peatland (i.e. Garzweiler Seam). Within the Garzweiler Seam, restricted sand lenses indicate a lagoonal or estuarine depositional environment (6). Regional correlation with adjacent wells establishes that shallow-marine conditions were widespread across the Lower Rhine Basin in middle Serravallian times. The shoreline profile, characterised by both tidal and wave activity and influenced by fluvial input from the adjacent Rhenish Massif, is indicative of the complexity of the coastal depositional setting within the Lower Rhine Basin.
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McSweeney, SL, DM Kennedy e ID Rutherfurd. "A geomorphic classification of intermittently open/closed estuaries (IOCE) derived from estuaries in Victoria, Australia". Progress in Physical Geography: Earth and Environment 41, n.º 4 (26 de maio de 2017): 421–49. http://dx.doi.org/10.1177/0309133317709745.
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A large proportion of estuaries along microtidal wave-dominated coastlines worldwide have entrances that intermittently close to the ocean when tidal currents and fluvial discharge are insufficient to erode sediment delivered onshore by waves. In this study, these systems are termed “intermittently open/closed estuaries” (IOCE) in order to include all estuaries which intermittently close to the ocean. IOCE do not fit neatly into existing generalized estuary classification models and have been traditionally recognized as a single estuary type that constitute a rare subset of wave-dominated estuaries. In this study, 111 estuaries in Victoria, Australia, are used to develop a classification model that delineates between different IOCE types. This was undertaken using historic aerial imagery and quantification of the estuary channel width, catchment area, lagoon dimensions and tidal prism derived from remotely sensed data. Field surveying of entrance morphology was undertaken for a subsample of 35 IOCE characteristic of each section of the coast and which had detailed entrance condition records. Using this subset, IOCE were classified into three distinct types using multiple methods of statistical delineation (non-metric multidimensional scaling, hierarchical cluster analysis and distribution analysis). These three types are: (1) Type A, the largest IOCE which both close and open infrequently but for the longest durations; (2) Type B, medium sized IOCE which open and close several times per year for weekly to monthly durations; and (3) Type C (tidal creeks), the smallest IOCE located specifically in high rainfall, mountainous catchments and which exist in a predominantly open state. The three types of IOCE showed an order of magnitude difference in entrance closure duration as controlled by variations in the catchment area, tidal prism volume, dimensions of the estuarine lagoon and the entrance channel at the mouth. The classification is also applicable to wave-dominated coastlines internationally where IOCE are present.
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Erfiko, Muhammad Fery, Sugeng Widada e Warsito Atmodjo. "Pemetaan Pola Sebaran Sedimen Dasar Di Perairan Wedung, Demak". Indonesian Journal of Oceanography 5, n.º 2 (13 de julho de 2023): 132–40. http://dx.doi.org/10.14710/ijoce.v5i2.16660.
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Perairan Wedung merupakan salah satu perairan dengan tingkat sedimentasi yang cukup tinggi. Hal ini dikarenakan banyaknya muara sungai yang mendepositkan sedimen di perairan tersebut, diantaranya adalah Sungai Jajar, Gojoyo, dan Saklenting. Muara sebagai penghubung antara sungai dengan laut, cenderung berpotensi terjadinya sedimentasi karena sedimen dari sungai dan dari laut akan bertemu di muara tersebut sehingga terjadi pendangkalan.Tujuan penelitian ini adalah mengetahui karakteristik sedimen dan pola sebaran sedimen dasar di Perairan Wedung, Demak. Parameter yang diteliti antara lain sedimen dasar, arus, pasang surut, dan batimetri. Metode yang digunakan metode shieving kering dan basah, pemetaan dengan ArcGIS 10.3 dan pemodelan menggunakan MIKE 21. Hasil dari penelitian ini menunjukkan sebaran sedimen adalah jenis lanau, lanau pasiran, pasir, dan pasir lanauan. Kecepatan arus berkisar 0,000029 – 0,086279 m/s dengan jenis arus pasang surut. Kondisi batimetri landai dengan kedalaman 0 – 30 m.AbstractThe Wedung waters exhibit a relatively elevated sedimentation rate. This occurrence can be attributed to the substantial quantity of sediment deposited in these waters by various river estuaries, such as the Jajar, Gojoyo, and Saklenting Rivers. The estuarine environment, serving as a transitional zone between fluvial and marine systems, exhibits a propensity for sediment accumulation due to the confluence of riverine and marine sediment, leading to the phenomenon of siltation. The objective of this investigation was to ascertain the properties and spatial arrangement of sedimentary deposits located at Wedung Waters, Demak. The parameters that were examined encompassed bed load sediment, currents, tides, and bathymetry. The employed techniques encompass dry and wet sieving methodologies, cartographic representation through ArcGIS 10.3, and simulation via MIKE 21. The findings of this investigation suggest that the sediment distribution comprises a combination of silt and sand. The present velocity spectrum, including tidal currents, spans from 0.000029 to 0.086279 meters per second. The bathymetry conditions exhibit a sloping topography, characterized by a depth range of 0 to 30 meters.
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Fielding, Christopher R., W. John Nelson e Scott D. Elrick. "Sequence stratigraphy of the late Desmoinesian to early Missourian (Pennsylvanian) succession of southern Illinois: Insights into controls on stratal architecture in an icehouse period of Earth history". Journal of Sedimentary Research 90, n.º 2 (26 de fevereiro de 2020): 200–227. http://dx.doi.org/10.2110/jsr.2020.10.
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ABSTRACT Uncertainty persists over whether repetitive stratal rhythms in the Pennsylvanian of Euramerica (so-called “cyclothems”) were externally forced, in all likelihood by waxing and waning of glacial ice centers on Gondwana, or were controlled by autogenic processes. A key to resolving this dispute is the lateral extent of the individual cyclothems, with broad regional extent (beyond the plausible breadth and length of individual depositional systems such as deltas) arguing in favor of an external forcing control. This study provides a sedimentological and sequence stratigraphic analysis of the middle Pennsylvanian (Desmoinesian to early Missourian in North American stratigraphic terminology, Moscovian to early Kasimovian in the terms of the global stratigraphic nomenclature) succession of the southern Illinois Basin in Illinois, Indiana, and Kentucky, eastern USA. An array of eleven lithofacies is recognized, recording deposition of clastic, humic organic, and bioclastic carbonate sediments on a broad, low-gradient, low-paleolatitude shelf and coastal plain that were undersupplied by sediment. These facies are arranged into thirteen repetitive vertical cycles (sequences), each of which can be traced across the entire basin west to east (perpendicular to the paleoslope direction) across a distance of 250 km. Sequences are bounded by erosion surfaces that define 1–4 km-wide, deeply incised valley-fills (IVFs) that are mostly elongate towards the south-southwest, the dominant direction of paleoflow. In the west–east direction, valley erosion surfaces pass laterally into well-developed paleosols, incised locally by smaller channels. Each of these surfaces is laterally persistent across the basin. IVFs comprise multi-story bodies of conglomerate–breccia and sandstone, passing upward into heterolithic sandstone–mudrock associations, recording fluvial and later estuarine environments. Coal bodies typically occur at the tops of IVFs and are interbedded with heterolithic facies recording tidal influence, indicative of initial flooding by the sea. They are in turn overlain by estuarine and marine mudrocks and bioclastic carbonates, recording the maximum extent of marine flooding in a cycle. Each sequence is completed by heterolithic to sandstone-dominated facies of deltaic aspect that are typically truncated by the next erosion surface (sequence boundary). Plausible modern analogs suggest that sea-level excursions were of the order of 20–40 m. The great lateral persistence of not only the thirteen sequences, but also many of their component beds, argues strongly for an external control on sediment accumulation. Eccentricity-paced glacial cycles in Gondwana are invoked as the most likely cause of the cyclicity. The low-accommodation context of the Illinois Basin (average accumulation rate 6 cm/ky) contributed to the incomplete, condensed, and strongly top-truncated nature of preserved sequences.
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Gorter, John D. "SEQUENCE STRATIGRAPHY AND THE DEPOSITIONAL HISTORY OF THE MURTA MEMBER (UPPER HOORAY SANDSTONE), SOUTHEASTERN EROMANGA BASIN, AUSTRALIA: IMPLICATIONS FOR THE DEVELOPMENT OF SOURCE AND RESERVOIR FACIES". APPEA Journal 34, n.º 1 (1994): 644. http://dx.doi.org/10.1071/aj93049.
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The Hooray Sandstone (Namur Sandstone Member and overlying Murta Member) was deposited during the Early Cretaceous in southwestern Queensland and northeastern South Australia. A sequence stratigraphie model for the Hooray is proposed. The basal beds of the Hooray Sandstone are the braided fluvial deposits of the Namur Sandstone Member, deposited during the late Berriasian and earliest Valanginian on a Type 1 sequence boundary developed during the 131.5 Ma sea level lowstand. Two sequences are recognised within the Namur (Namur Nl and N2) with a Type 1 sequence boundary interpreted within the member (128.5 Ma sea level fall). The upper Namur is gradational with the lower Murta Member M6 which forms a transgressive systems tract. The M5 and M4 are highstand systems tract sediments deposited over the maximum flooding surface at the base of the M5 (127.5 Ma condensed section). Low sea levels led to incision of channels basinwards of exposed basement rocks at the end of M4 time (about 126 Ma). Sea level rise led to the gradual Willing of these channels until the southeastern highlands were drowned but islands in the southeast contributed vitrinitic material during mid M3 time, which formed the source for the oil in the Nockatunga area. Reservoir sandstones are developed within the basal M3 incised valley fill sands and in the transgressive microtidal barrier facies sands at the top of the M3. The former can produce stratigraphic traps, whereas the latter form structural traps. Reservoir quality is probably best in the thicker mid 'estuarine' sands due to tidal reworking, and generally poorer in the barrier facies due to little winnowing of fines because of the low tidal range, weak wave activity, and gene-contemporaneous carbonate cementation. During later M3 time, transgression led to the landward movement of barrier bars, forming a generally sheet-like sand body. The top M2 and M3 barriers probably formed in a microtidal environment under a seasonal climate with periodic storm conditions. Following inundation of the islands during M2 and Ml times, organic matter supplied to the Nockatunga area was dominantly finely comminuted, bacterially-altered plant matter and algal material that forms a potentially rich but immature oil source. The 'hot gamma' shales of the Ml are interpreted as the 123.5 Ma condensed section.
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Tye, Robert S., Donald R. Lowe e J. J. Hickey. "Ediacaran (Vendian)-period alluvial and coastal geomorphology applied to development of Verkhnechonskoye and Yaraktinskoye fields, East Siberia, Russian Federation". Journal of Sedimentary Research 90, n.º 1 (22 de janeiro de 2020): 67–101. http://dx.doi.org/10.2110/jsr.2020.8.
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ABSTRACT Ediacaran-age (635–542 Ma) oil-bearing strata in the Yarakta Horizon at the Verkhnechonskoye and Yaraktinskoye fields, East Siberia, consist of conglomerate, sandstone, dolomitic sandstone, and mudstone overlying and onlapping igneous to metasedimentary highlands of the East Siberia craton. Initial drainage networks formed within structurally defined valleys, and early deposition occurred in localized alluvial to shallow-marine depositional systems. Base-level-controlled depositional cycles aggraded the valleys; thus, as valleys aggraded, they buried interfluves and coalesced forming broad alluvial and coastal plains. Three to seven bedsets of variable net-to-gross content constitute a genetic cycle. Depositional cycles varied locally, as nine and eight cycles separated by decimeter- to multi-meter-thick mudstones are defined at Verknechonskoye and Yaraktinskoye, respectively. Within one genetic cycle, facies associations grade basinward from alluvial (channel-bar, channel-fill, floodplain, playa, and crevasse-splay) to shallow marine (sabkha, tidal-flat, estuarine-channel, and poorly developed shoreface). Coarse-grained lithofacies are typically arranged in decimeter- to meter-scale bedsets with sharp to scoured bases. Bedsets commonly, but not always, show an upward decrease in grain size, bed thickness, and scale of sedimentary structure. Typically, medium-grained sandstones exhibit low-angle cross bedding and are gradationally overlain by fine-grained sandstones exhibiting scour-and-fill, cuspate-ripple lamination, climbing-ripple lamination, and parallel lamination. Clay clasts and small pebbles are accessories. Interbedded mudstones, siltstones, and sandstones show ripple cross bedding, wavy to lenticular bedding, abundant soft-sediment deformation (e.g., shear, fluid-escape, slump features), and slickensides. Thin-bedded sandstones are micaceous and contain granule-size mud chips. Some mudstones exhibit crinkled to parallel laminae indicative of algal growth. Sandstone fills mudcracks. Interbedded green and black mudstones, plus pyrite and siderite cements, indicate alternating redox conditions. Alluvial facies have patchy quartz, anhydrite, and carbonate cements. Marine-influenced facies show early and well-developed quartz cement as well as abundant halite. Gypsum and halite dissolution formed secondary pores. Calculated estimates of fluvial-channel dimensions and sinuosities indicate that despite the lack of vegetation, fluvial channels in the Yarakta Horizon were shallow and relatively narrow, moderately sinuous, and exhibited varying degrees of mud-prone overbank deposition. Recognition and correlation of flooding surfaces and channel diastems bounding genetically related strata identified multiple stratigraphic compartments in each field. Porosity loss at chronostratigraphic boundaries accounts for complex water, oil, and gas contacts. Economic field development is hampered by locally varying reservoir quality and sandstone continuity caused by its channelized and onlapping stratigraphy and diagenesis. Reservoir simulation of varying geostatistical models demonstrate that differing porosity-distribution methods had little effect on estimates of in-place hydrocarbon volumes. Model differences in porosity and permeability distribution and lithofacies connectivity show large variations in recovery factor and productivity/injectivity.
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Bastos, Ana Teresa Cordeiro Cid, e Elisabete de Santis Braga. "Different silicon forms sinalize an input of urbanized river and indicate the presence of phytoplankton with silicon structures in the tropical coastal area of Recife (PE-Brazil)". Brazilian Journal of Oceanography 66, n.º 1 (março de 2018): 104–14. http://dx.doi.org/10.1590/s1679-87592018149206601.
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Abstract The urbanized areas mark its presence in the hydrological systems with some biogeochemical signs including silicon inputs. Natural influence of leaching and erosion is done by silicate contribution and sometimes, the agriculturally soil contains microphytoliths and contributes with biogenic silica. Once in the hydrological system, the silicon can integrate the biogeochemical cycles showing a balance or not between inorganic and biological forms that reveals a tendency of processes that occur in each sector of the estuarine-marine interface. This study aims to evaluate the impact of a heavily polluted/urbanized river, whose input can be evidenced by the contribution of different forms of silicon that can evidence the terrestrial contribution, erosion process, the presence of phytoplankton species with siliceous structures, mainly associated to diatoms and also, to study the river plume spreading on the coastal area by undertaking silicon profiles in the region adjacent to the river mouth. The coastal region of Recife is under influence of fluvial inputs from Capibaribe and Beberibe rivers verified by observed low salinity (min. 33.93). The distribution of silicon forms showed sectorial variation, and the maximum values were dissimilar. Dissolved silicate reached 14.40 µmol L-1, lithogenic silicon (LSi) maximum of 25.76 µmol L-1 and biogenic silica (BSi) reaching 7.39 µmol L-1 near the river mouth toward the sea, evidencing the river influence coming from the west, achieving the port barrier at the end and propagating in the sea toward northeast. Due to higher nutrient availability in the stations nearest to the coast, primary production was encouraged with evidencing by high values of chlorophyll-a associated to silicate (r=0.71) and to BSi (r=0.44). In the stations more distant to the coast, the forms of silicon showed very low concentrations and BSi/Chlorophyll-a showed negative correlation associated with chlorophyll-a concentrations evidencing the participation of non-silicon actors in the primary production in medium depth in oligotrophic tropical waters.
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Menier, David, Bernadette Tessier, Jean-Noël Proust, Agnès Baltzer, Philippe Sorrel e Camille Traini. "The Holocene transgression as recorded by incised-valley infilling in a rocky coast context with low sediment supply (southern Brittany, western France)". Bulletin de la Société Géologique de France 181, n.º 2 (1 de março de 2010): 115–28. http://dx.doi.org/10.2113/gssgfbull.181.2.115.
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Abstract A combination of morphobathymetric studies, very high-resolution seismics, core sampling and radiocarbon age data is used to investigate the latest stage of the sedimentary infilling of incised valleys in southern Brittany, related to the Holocene transgression. Owing to the bedrock morphology of this highly irregular rocky coast, two main types of valleys are defined by topographic rocky highs parallel to the coastline: 1) wide and rather shallow incised valleys offshore from a topographic sill, 2) narrow and relatively deep valleys between the sill and the coast (ria-type valley). The sedimentary infilling in both types of valleys becomes highly differentiated as the transgression advances onto the coastal area. In the wide valley seaward of the topographic sill, the infilling consists mainly of offshore heterolithic facies while, in the ria-type valley, most of the infill is composed of brackish mudflat deposits and estuarine tidal muddy sands. As the transgression proceeds, the rocky highs are flooded and the whole area is finally covered by the offshore facies. Radiocarbon dating indicates that: 1) the marine ravinement surface is highly diachronous (a few thousand years cross-shore); 2) the top of the offshore facies, coarser and very shelly, represents an episode of condensed sedimentation from about 3000 to 4000 years ago, amalgamating the maximum flooding surface (MFS) and the highstand systems tract (HST). However, we observe a muddy drape, strongly bioturbated in places, in the most proximal areas, overlying the offshore facies. It is thought to represent the modern and most recent stage of sedimentary infilling. This mud cover is made of fine-grained sediments of fluvial and biological origin, and is interpreted as a prograding HST. It reflects an increased influx, partly due to human activities. Finally, the main features of incised valley sedimentary infilling in a rocky coast context with low sediment supply can be characterized by (i) the very strong control of bedrock morphology, (ii) the diachronous character of the transgression, (iii) the late position of the MFS, and (iv), the highly reduced volume of the HST.
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Griffioen, J., G. Klaver e W. E. Westerhoff. "The mineralogy of suspended matter, fresh and Cenozoic sediments in the fluvio-deltaic Rhine–Meuse–Scheldt–Ems area, the Netherlands: An overview and review". Netherlands Journal of Geosciences - Geologie en Mijnbouw 95, n.º 1 (2 de fevereiro de 2016): 23–107. http://dx.doi.org/10.1017/njg.2015.32.
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AbstractMinerals are the building blocks of clastic sediments and play an important role with respect to the physico-chemical properties of the sediment and the lithostratigraphy of sediments. This paper aims to provide an overview of the mineralogy (including solid organic matter) of sediments as well as suspended matter as found in the Netherlands (and some parts of Belgium). The work is based on a review of the scientific literature published over more than 100 years. Cenozoic sediments are addressed together with suspended matter and recent sediments of the surface water systems because they form a geoscientific continuum from material subject to transport via recently settled to aged material. Most attention is paid to heavy minerals, clay minerals, feldspars, Ca carbonates, reactive Fe minerals (oxides, siderite, sulphides, glauconite) and solid organic matter because they represent the dominant minerals and their properties form a main issue in subsurface and water management. When possible and relevant, the amounts, provenance, relationship with grain size distribution, early diagenesis and palaeohydrological evolution are described. Tables with statistical data about the mineral contents and isotopic composition of carbonates and organic matter are presented as overviews. The review on the mineralogy of Dutch fluvial and marine environments is more extensive than that for the other sedimentary environments because the first two have been studied much more intensively than the others and they also form the larger part of the Dutch deposits. The focus is on the natural background mineralogy of Dutch sediments, but this is hard for recent sediments, largely because the massive hydraulic infrastructure present in the Netherlands has probably also affected the mineralogy and geochemistry of sediments deposited in recent centuries. Many findings are summarised, several of which lead to more general insights for the Dutch situation. Ca carbonates in sediments often have several provenances and thus must be considered as mixtures. Dolomite is commonly present in addition to calcite. The importance of biotite as weatherable mica is unclear. Weathering of heavy minerals plays some role but it is unclear in which way it affects the heavy mineral associations. Clays are usually dominated by illite, smectite and their interstratified variant, while kaolinite is usually below 20% and chlorite below 5%. Vermiculite is a minor constituent in fluvial clays and its illitisation presumably happens during early diagenesis in the marine environment. Opaque Fe hydroxides can be present in addition to Fe oxyhydroxide coatings and both will play a role in redox chemistry as reactive Fe minerals. Feldspars in marine sediments must be present but they have not been properly studied. The genesis of rattle stones and carbonate concretions has not been completely elucidated. The fraction of terrigeneous organic matter in estuarine and coastal marine sediments is substantial. The available data and information are spread irregularly over the country and the reviewed information discussed in this paper is derived from relatively small-scale studies dealing with a limited amount of analysed samples. Much information is available from the Scheldt estuaries in the southwestern part of the Netherlands partly due to the severe contamination of the Western Scheldt in recent decades.
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Gonzalez, Wilma B. Aleman, Jean M. Self-Trail, W. Burleigh Harris, Jessica Pierson Moore e Kathleen M. Farrell. "Depositional sequence stratigraphy of Turonian to Santonian sediments, Cape Fear arch, North Carolina Coastal Plain, USA". Stratigraphy 16, n.º 1 (11 de dezembro de 2020): 293–314. http://dx.doi.org/10.29041/strat.17.4.293-314.
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ABSTRACT: A new sequence stratigraphic framework for Turonian to Santonian (94-84 Ma) sediments is established using data from the USGS Kure Beach and Elizabethtown cores collected from the Atlantic Coastal Plain of North Carolina (NC). These sediments represent some of the oldest marine units deposited on the southeastern Atlantic Coastal Plain and record the early development of a clastic wedge atop crystalline basement. Sediments were deposited as transitional marginal-marine to marine units in a complex interplay of fluvial, estuarine, and shelf environments. Repetitive lithologies and minimal biostratigraphic control requires an integrated analysis of grain-size data, geophysical logs, biostratigraphy, and 87Sr/86Sr isotopic data to identify systems tracts and establish a sequence stratigraphic framework. From this integrated approach, three Turonian to Santonian sequences in the Elizabethtown core and six in the Kure Beach core are identified. The new sequences from oldest to youngest are Clubhouse II, Fort Fisher I, Fort Fisher II, Collins Creek I, Collins Creek II, Pleasant Creek I, and Pleasant Creek II. Sequences from North Carolina document significant shifts of global and regional sea-level during greenhouse conditions in the early Late Cretaceous. Maximum sea-level rise occurred globally during the early Turonian and is documented from the marine sediments of the Clubhouse II sequence. This sequence is unconformably overlain by terrestrial sediments deposited during a major fall in sea level and maximum progradation of the shoreline, as evidenced by the Fort Fisher I sequence. Global sea-level rise in the Coniacian resulted in the deposition of the Fort Fisher II sequence, which is present only in the Kure Beach core. Local marine circulation and erosion on the shelf is suggested by the absence of the Collins Creek I sequence at Kure Beach; this sequence is present only in the up-dip Elizabethtown core. Activation of a possible buried fault structure along the Cape Fear arch resulted in the formation of a regional depocenter during the late Coniacian to early Santonian and is reflected in the unusual thickness of the Collins Creek II and Pleasant Creek I sequences. The return to a more global sea-level influence occurred in the late Santonian with the deposition of the Pleasant Creek II sequence. A comparison of temporal distribution of sequences in the Elizabethtown and Kure Beach cores to corresponding sequences in New Jersey indicates significant differences in erosional and tectonic processes in the Cape Fear region during the Turonian and Santonian.
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Tamasauskas, Priscilla Flores Leão Ferreira, Larisse Fernanda Pereira de Souza, Aline Maria Meiguins de Lima, Márcia Aparecida da Silva Pimentel e Edson José Paulino da Rocha. "Métodos de avaliação da influência das áreas ripárias na sustentabilidade hidrológica em bacias hidrográficas no nordeste do estado do Pará / Assessment methods of the influence of riparian areas in hydrologic sustainability (...)". Caderno de Geografia 26, n.º 45 (30 de dezembro de 2015): 172. http://dx.doi.org/10.5752/p.2318-2962.2016v26n45p172.
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<p>As bacias hidrográficas do rio Caripi e do Igarapé Açu localizam-se nos municípios de Marapanim e Igarapé Açu, compondo o conjunto de bacias costeiras de comportamento fluvio-estuarino que drenam a região nordeste do estado do Pará. O processo de uso e ocupação do solo na região tem mostrado uma tendência de ameaça a manutenção do potencial hídrico destas bacias, por esta razão este trabalho objetivou avaliar diferentes métodos de determinação da área de floresta ripária e sua relação com a sustentabilidade hídrica. A metodologia consistiu em definir as áreas de floresta ripária a partir de dois métodos de análise espacial e a aplicação do resultado no cálculo do Índice de Sustentabilidade Hídrica. Os resultados obtidos demonstram que as bacias encontram-se em situação de moderada sustentabilidade, porém a distribuição das classes de cobertura e uso do solo indicam que existe a fragmentação dos sistemas florestais e a redução das áreas que deveria ser de floresta ripária. As técnicas adotadas diferem quanto a nível de cobertura da informação, indicando que a proximidade do modelo hidrológico da bacia depende das variáveis consideradas e da precisão do processo de análise espacial adotado.</p><p><strong>Palavras–chave:</strong> análise espacial, paisagem, uso e cobertura do solo.</p><p> </p><p><strong>Abstract </strong></p><p>The basins of Caripi and Igarapé Açu rivers belong to the municipalities of Marapanim and Igarapé Açu in Para state. They are part of the coastal catchment system with fluvial-estuarine behavior that drain the northeastern state of Para. The process of land use and land occupation represent a threat on the potential of water maintenance in these basins. Therefore, this study evaluated different methods for determining the riparian forest area and its relation to water sustainability. The methodology adopted aimed to identify the areas of riparian forest with two spatial analysis methods and applies the Hydric Sustainability Index. The results obtained show that the basins are in a situation of moderate sustainability, but the distribution of land cover and land use indicates a fragmentation of forest systems and the reduction of areas that should be a riparian forest. The adopted techniques differ in the level of coverage of information, where the precision of hydrological model depends on the chosen variables and the accuracy of the spatial analysis process used.</p><p><strong>Keywords</strong>: spatial analysis, landscape, land use and land cover.</p><p> </p>
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Bilotte, Michel, Laurent Koess e Elie-Jean Debroas. "Relationships between tectonics and sedimentation on the northeastern margin of the Subpyrenean trough during the late Santonian". Bulletin de la Société Géologique de France 176, n.º 5 (1 de setembro de 2005): 443–55. http://dx.doi.org/10.2113/176.5.443.
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Abstract In the eastern part of the Aquitaine Basin and to the south of the Toulouse high, the Subpyrenean trough is a narrow trench oriented N110°E to N130° E. The deposits on the northeastern side of this depression are preserved in the autochthonous Mesozoic cover of the Variscan Mouthoumet Massif, but also in the parautochthonous or allochthonous tectonic units that fringe to the north (Camps – Peyrepertuse slice, fig. 2) the North Pyrenean frontal thrust. From the Middle Cenomanian to the Lower Santonian included (96 to 85 Ma ago), the sedimentation in the Mouthoumet Massif indicates shallow marine carbonate or mixed (carbonate to terrigenous) conditions. The different facies depend mainly on two parameters : the variations of the accommodation space for sedimentation and the location of the numerous rudist buildups. The deposits are first organized in a homoclinal ramp until the Turonian. From the Coniacian up to the early Santonian, drowned platform patterns prevail. During the late Santonian and more precisely around 85 Ma with an other event around 84 Ma, the Mouthoumet Massif and its cover broke up under tectonic stresses. Positive and negative topographies reactivate the Variscan fault system. Platform – slope/basin morphologies substituted the preceeding ramp and drowned platform morphology. Looking to the south and in the direction N120°E, the distal slope received gravitational and turbiditic sediments called the Grès de Labastide (fig. 7). The sediment supply shifted from north to south and from east to west. To the north of this slope, the platform itself broke up into a mosaic of rhomboedric blocks, leading to a graben and horst morphology. Those units are clearly different according to the character of their sedimentary facies, deltaic or reefal (Montagne des Cornes, Calcaires de Camps – Peyrepertuse). The detailed stratigraphic and sedimentologic studies of some of these systems reveal a tectono-sedimentary evolution involving two successive cycles Ss1 (lower Upper Santonian) and Ss2 (Uppermost Santonian). In the western part of the Mouthoumet Massif this cyclic evolution is recorded from south to north, on the Parahou slope, the Rennes-les-Bains graben and the Bugarach horst. The lower cycle Ss1, located on the Rennes-les-Bains graben, is approximatively 85 Ma to 84 Ma in age. It starts with reworked deposits (lowstand systems tract) made up of sometimes several m3 elements derived from former sedimentary deposits (from Turonian up to Lower Santonian) even when the same deposits are in place on the adjacent horsts (e.g. the eastern horst of Bugarach). Those reworked deposits fill the bottom of the graben, principally in the transit zones (debris-flows of the Conglomerat de la Ferrière), or in the Parahou slope (slumps and debris-flows of the Cascade des Mathieux); then the deltaic complex of Rennes-les-Bains covers the older chaotic deposits; the blue marls and the overlying sandy facies (transgressive and highstand systems tracts) related to prodelta and deltafront deposits represent the infilling of the Rennes-les Bains graben. The upper cycle Ss2 developed probably between 84 Ma to 83,5 Ma; its geographical extension overlaps the limits of the lower cycle (e.g. the Bugarach horst), but its sedimentary organisation is still the same including: on the Parahou slope debris-flow and intrabasinal reworking (Conglomérat des Gascous: lowstand systems tract); on the northern platform transgressive and highstand systems tracts, present in the Montagne des Cornes delta where the Marnes bleues de Sougraigne represent the prodelta deposits, and the terrigenous and rudist buildups of the delta front deposits (fig.7). The final infilling results from the spreading from NE to SW, of the (estuarine ? to) fluvial deposits of the Grès d’Alet Formation at around 83 Ma. In the eastern part of the Mouthoumet Massif, sedimentary development is punctuated by tectonic events. Nevertheless, it is possible to identify in some outcrops the main elements of the two tectono-sedimentary cycles. – The cycle Ss1 is partly preserved in the genetic sequence which links the Calcaires de Camps-Peyrepertuse (shelf margin wedge systems tract) and the Marnes du Pla de Sagnes (transgressive systems tract). The cycle Ss2 is only known through different facies of the Grès de Labastide Formation: reworked deposits on the slope; coarse-grained silicoclastic deposits on the transit zones. – In the cycle Ss1 differences appear between the western and the eastern parts of the Mouthoumet massif. When in the western area deltaic conditions prevailed, in the eastern area a shallow carbonate and buildup facies developed. Such differences disappear in the cycle Ss2 by the general establishment of fore slope deltaic deposits. The geodynamic reconstruction resulting from plate kinematics indicates a major change between the early Coniacian (89 Ma) and the Middle Campanian (79 Ma), when the sinistral/divergent motion of Iberia with respect to stable Europe turned to a dextral/convergent movement. The tectono-sedimentary events presented here took place during this period (85 Ma to 83 Ma). The tectono-sedimentary evolution of the subpyrenean trough and the shift of the European and Iberian plates are thought to be intimately linked. The new chronological and geodynamical data proposed herein show that the genesis and the evolution of the subpyrenean sedimentary processes related to the northern Aquitanian margin of the Subpyrenean trough allow to draw some basic conclusions: – the opening of the Subpyrenean trough occurred in two steps, the first around 85 Ma and the second around 84 Ma; – this caused a change in the sedimentary setting with platform environments replacing the earlier ramp geometry; – the Subpyrenean trough formed and evolved under transtensive tectonic conditions; – during the late Santonian two tectono-eustatic sequences marked the former stages of the eastward opening and infilling of this basin; – the diachronous infilling which began here around 83,5 Ma prograded to the western Plantaurel and Petites-Pyrénées area; – no significant northward shifting of the depositional-axis of the Senonian basins occurred; – only a gradual westward shift of the depositional centers, along the subpyrenean direction of the slope area (N110°E to N130°E) was noticed.