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1
Jackson, Christopher A.-L., Andrew E. McAndrew, David M. Hodgson e Tom Dreyer. "Repeated degradation and progradation of a submarine slope over geological timescales". Journal of Sedimentary Research 91, n.º 1 (31 de janeiro de 2021): 116–45. http://dx.doi.org/10.2110/jsr.2020.77.
Resumo:
ABSTRACT Submarine slopes prograde via accretion of sediment to clinoform foresets and degrade in response to channel or canyon incision or to mass-wasting processes. The timescales over which progradation and degradation occur, and the large-scale stratigraphic record of these processes, remain unclear due to poor age constraints in subsurface-based studies and areally limited exposures of exhumed systems. We here integrate 3D seismic reflection and borehole data to study the geometry and origin of ancient slope canyons developed in late Mesozoic strata of the Måløy Slope, offshore Norway. Slope degradation and canyon incision commenced during the late Kimmeridgian, coincident with the latter stages of rifting. Later periods of canyon formation occurred during the Aptian to Albian and the Albian to Cenomanian, during early post-rift subsidence. The canyons are straight, up to 700 m deep, and 10 km wide on the upper slope and die out downdip onto the lower slope. The canyons trend broadly perpendicular to and crosscut most of the rift-related normal faults, although syn-filling fault growth locally helped to preserve thicker canyon-fill successions. The headwalls of the oldest (late Kimmeridgian) canyons are located at a fault-controlled shelf edge, where younger canyons overstep this fault, which was inactive when they formed, extending across the paleo-shelf. Downslope, Aptian to Albian canyons either erode into the older, late Kimmeridgian to Barremian canyon fills, forming a complicated set of unconformities, or in the case of the Albian to Cenomanian canyons, die out into correlative conformities. Boreholes indicate that the canyon bases are defined by sharp, erosional surfaces, across which we observe an abrupt upward shift from shallow- to deep-marine facies (i.e., late Kimmeridgian canyons), or deep marine to deep marine facies (Aptian to Albian and Albian to Cenomanian canyons). Missing biostratigraphic zones indicate the canyons record relatively protracted periods (c. 2–17 Myr) of structurally enhanced slope degradation and sediment bypass, separated by > 10 Myr periods of deposition and slope accretion. The trigger for slope degradation is unclear, but it likely reflects basinward tilting of this tectonically active margin, enhanced by incision of the slope by erosive sediment gravity flows. The results of our study have implications for the timescales over which large-scale slope progradation and degradation may occur on other tectonically active slopes, and the complex geophysical and geological record of these processes. We also show that canyon formation can cause large volumes of margin-derived sediment to bypass proximal sub-basins within rifted terranes, an important process not currently captured by marine rift-basin tectono-stratigraphic models.
2
Pollock, R. M., Q. Li, B. McGowran e S. C. Lang. "OLIGO-MIOCENE CANYONS IN THE GAMBIER SUB-BASIN, SOUTHERN AUSTRALIA—DEEPWATER ANALOGUES FOR PETROLEUM EXPLORATION". APPEA Journal 42, n.º 1 (2002): 311. http://dx.doi.org/10.1071/aj01017.
Resumo:
The Gambier Sub-basin lies on the southern Australian passive continental margin that formed during continental breakup and seafloor spreading between the Australian and Antarctic plates. In addition to the numerous modern submarine canyons reported on the southern Australian margin, three palaeo-canyon systems have been identified within the Gambier Limestone of the South Australian Gambier Sub-basin. Favourable environmental conditions during the Oligocene and Early Miocene led to deposition of the Gambier Limestone, a widespread, prograding extra-tropical carbonate platform. A world-wide glacio-eustatic sea level fall in the Early Oligocene exposed the shelf in the Gambier Subbasin, causing widespread erosion and minor fluvial incision on the shelf and subsequent formation of nick points at the shelf edge. During the following marine transgression later in the Oligocene, the shelf was inundated and the nick points provided conduits for erosive turbidity currents to enlarge the canyons to the spectacular dimensions observed on seismic data. No less than 20 successive canyon cut and fill events ranging from Late Oligocene to Middle Miocene have been observed and mapped on seismic data across the shelf in the Gambier Sub-basin. The thick, dominantly fine-grained carbonate sheet logically represents a potential regional seal to underlying clastic reservoirs. However, the possibility exists for carbonate reservoir sands to be present within the palaeo-canyons, sealed by surrounding fine-grained carbonates. Although no hydrocarbons have yet been identified in the carbonates of the Gambier Sub-basin, the canyons provide an analogue useful for establishing the scale, internal architecture and geometry of canyon fill systems.
3
Siedl, Wolfgang, Philipp Strauss, Reinhard F. Sachsenhofer, Mathias Harzhauser, Thomas Kuffner e Matthias Kranner. "Revised Badenian (middle Miocene) depositional systems of the Austrian Vienna Basin based on a new sequence stratigraphic framework". Austrian Journal of Earth Sciences 113, n.º 1 (1 de janeiro de 2020): 87–110. http://dx.doi.org/10.17738/ajes.2020.0006.
Resumo:
AbstractThis paper presents a revised sequence stratigraphy for the lower, middle and upper Badenian depositional systems of the Austrian Vienna Basin based on the integration of 3D seismic surveys and well data. The study area in the central and northern part of the Austrian Vienna Basin is covered with 3D seismic data. According to a new sequence stratigraphic framework established in the southern part of the Vienna Basin, the Badenian is subdivided into three 3rd order depositional sequences. For each sequence, paleogeographic maps are created, representing coeval depositional systems within a chronostrati-graphic interval. Lower Badenian sediments of the 1st sequence (Ba1) represent fillings of the pre-Badenian sub-basins with a major change of sediment transport direction. The early stage of the 1st sequence is dominated by subaerial braided river deposits which use two pronounced canyon systems (Mistelbach Canyon and Reinthal Canyon) on the northwestern margin of the Vienna Basin as a bypass zone towards the marine depositional system of the North Alpine-Carpathian Foredeep. The late stage of the 1st sequence reflects the change from subaerial to marine depositional environments with main sediment influx from the west, creating two major eastwards prograding delta systems (Zistersdorf Delta and Mühlberg Delta). Depositional systems of the middle Badenian 2nd sequence (Ba2) reflect the interplay between ongoing extensional fault tectonics and major sea-level changes. Lower Badenian paleo-highs in the northern part are drowned during the 3rd sequence (Ba3), thus the Mühlberg Delta and the Zistersdorf Delta merge into one delta system. During the Ba3 the drowning of the Spannberg Ridge initiates a clockwise rotation of the Zistersdorf Delta. Thus, the former Zistersdorf Delta transforms into the Matzen Delta covering the Spannberg Ridge. Together with the Mühlberg Delta, they represent the last full marine depositional system of the eastward prograding paleo-Danube Delta in the Austrian Vienna Basin.
4
Ou, Xiaolin, Junjiang Zhu, Sanzhong Li, Yonggang Jia, Zhongjia Jia, Shengsheng Zhang, Shaoyu Zhang et al. "Submarine Geomorphological Features and Their Origins Analyzed from Multibeam Bathymetry Data in the South China Sea". Journal of Marine Science and Engineering 9, n.º 12 (12 de dezembro de 2021): 1419. http://dx.doi.org/10.3390/jmse9121419.
Resumo:
We processed the raw multi-beam bathymetry data acquired in the central and northeastern part of the South China Sea by eliminating noise and abnormal water depth values caused by environmental factors, and a high resolution bathymetric map with a 20-m grid interval was constructed. Various scales of seafloor geomorphological features were identified from the data, including an image of Shenhu canyon, which is located in the northern continental margin of the South China Sea; submarine reticular dunes in the north of the Dongsha atoll; submarine parallel dunes in the northeast of the Dongsha atoll; and several seamounts in the southwest sub-basin and in the east sub-basin. In the processing step, various anomalies in the multi-beam bathymetry data were corrected. The optimal swath filtering and surface filtering methods were chosen for different scales of seafloor topography in order to restore the true geomorphological features. For the large-scale features with abrupt elevation changes, such as seamounts (heights of ~111–778 m) and submarine canyons (incision height of ~90–230 m), we applied swath filtering to remove noise from the full water depth range of the data, and then surface filtering to remove small noises in the local areas. For the reticular dunes and parallel dunes (heights of ~2–32 m), we applied only surface filtering to refine the data. Based on the geometries of the geomorphological features with different scales, the marine hydrodynamic conditions, and the regional structure in the local areas, we propose that the Shenhu submarine canyon was formed by turbidity current erosion during the Sag subsidence and the sediment collapse. The submarine reticular dunes in the north of the Dongsha atoll were built by the multi-direction dominant currents caused by the previously recognised internal solitary waves around the Dongsha atoll. The submarine parallel dunes in the northeast of the Dongsha atoll were built by the repeated washing of sediments with the influence of the tidal currents and internal solitary waves. The conical, linear and irregular seamounts identified from the bathymetry data were formed during the spreading of the southwest sub-basin and the east sub-basin. The identified seamounts in the multi-beam bathymetry data are correlated to deep magmatic activities, the Zhongnan transform fault and the NE-trending faults.
5
Zhou, Qingjie, Xianfeng Li, Jianglong Zheng, Xishuang Li, Guangming Kan e Baohua Liu. "Inversion of Sub-Bottom Profile Based on the Sediment Acoustic Empirical Relationship in the Northern South China Sea". Remote Sensing 16, n.º 4 (8 de fevereiro de 2024): 631. http://dx.doi.org/10.3390/rs16040631.
Resumo:
This study focuses on the inversion of sub-bottom profile (SBP) data in the northern South China Sea using an empirical relationship derived from sediment acoustic data. The sub-bottom profile is primarily utilized for various marine applications, such as geological mapping and resource exploration. In this research, we present a study conducted in the northern slope canyon of the South China Sea. Firstly, we obtained the seabed reflection coefficient from sub-bottom profiles obtained by the autonomous underwater vehicle (AUV) detection system. Secondly, we utilized the acoustic empirical relationship in the northern South China Sea to establish relationship equations between the seabed reflection coefficient and the porosity, density, and average particle size of the sediment at a main frequency of 4 kHz (the AUV shallow profile main frequency). Then, using these equations, we were able to invert the physical parameters such as porosity, density, and average particle size of the seabed surface sediments. Finally, the inverted results are compared and analyzed by using the sediment samples test data. The overall deviation rate of the inverted physical parameters is within the range of ±10% when compared. The inverted results closely match the measured values, accurately reflecting the dynamic changes in the physical properties of seabed surface sediments. Notably, the average grain size is a direct indicator of the sediment particles size with smaller particles found in deeper water. The variation characteristics of sediment physical parameters align well with the variation of sediment types in the canyon, which is consistent with changes in the water depth, topography, and hydrodynamic conditions of the area. This further demonstrates the reliability of the inversion results.
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Knab, N. J., B. A. Cragg, E. R. C. Hornibrook, L. Holmkvist, R. D. Pancost, C. Borowski, R. J. Parkes e B. B. Jørgensen. "Regulation of anaerobic methane oxidation in sediments of the Black Sea". Biogeosciences 6, n.º 8 (7 de agosto de 2009): 1505–18. http://dx.doi.org/10.5194/bg-6-1505-2009.
Resumo:
Abstract. Anaerobic oxidation of methane (AOM) and sulfate reduction (SRR) were investigated in sediments of the western Black Sea, where upward methane transport is controlled by diffusion. To understand the regulation and dynamics of methane production and oxidation in the Black Sea, rates of methanogenesis, AOM, and SRR were determined using radiotracers in combination with pore water chemistry and stable isotopes. In the Danube Canyon and the Dnjepr palaeo-delta AOM did not consume methane effectively and upwards diffusing methane created an extended sulfate-methane transition zone (SMTZ) that spread over more than 2.5 m and was located in brackish and limnic sediment. Measurable AOM rates occurred mainly in the lower part of the SMTZ, sometimes even at depths where sulfate seemed to be unavailable. The inefficiency of methane oxidation appears to be linked to the paleoceanographic history of the sediment, since in all cores methane was completely oxidized at the transition from the formerly oxic brackish clays to marine anoxic sediments. The upward tailing of methane was less pronounced in a core from the deep sea in the area of the Dnjepr Canyon, the only station with a SMTZ close to the marine deposits. Sub-surface sulfate reduction rates were mostly extremely low, and in the SMTZ were even lower than AOM rates. Rates of bicarbonate-based methanogenesis were below detection limit in two of the cores, but δ13C values of methane indicate a biogenic origin. The most δ13C- depleted isotopic signal of methane was found in the SMTZ of the core from the deep sea, most likely as a result of carbon recycling between AOM and methanogenesis.
7
Wulff, Keiran. "DEPOSITIONAL HISTORY AND FACIES ANALYSIS OF THE UPPER JURASSIC SEDIMENTS IN THE EASTERN BARROW SUB-BASIN". APPEA Journal 32, n.º 1 (1992): 104. http://dx.doi.org/10.1071/aj91010.
Resumo:
Callovian to Tithonian syn-rift sediments in the eastern Barrow Sub-basin can be subdivided into five depositional sequences, each separated by regionally correlatable unconformities. Sequence boundary development can be closely related to periods of major changes in basin configuration associated with the sequential breakup of eastern Gondwanaland. Synchronism of major faulting with sequence boundary development during the early and late Callovian, mid Kimmeridgian, and mid Tithonian times supports tectonism being a dominant control on the development of Type 1 unconformities in the eastern Barrow Sub-basin.Upper Jurassic depositional sequences in the eastern Barrow Sub-basin, whether of tectonic or eustatic origin, consist primarily of lowstand systems tracts comprised, wholly or in part, of detached basin floor fan complexes, channelised and canyon-fed fan systems, slump deposits, outer shelf to slope deposits, and deep marine claystones. Inner shelf to shoreface sediments of the transgressive and highstand systems tracts are absent due to episodic, post-depositional uplift and erosion along the Peedamullah Shelf and Flinders Fault System during the Late Jurassic. The periods of uplift and erosion provided much of the sediment redeposited in basinal areas during lowstand times.Depositional models based on regional sequence stratigraphic studies can be integrated with local seismic stratigraphy to provide a mechanism for estimating likely reservoir quality, once controls on sedimentation (namely tectonics, eustasy, and sediment supply) are understood. This is demonstrated by the recognition of at least seven sandstone facies within the Upper Jurassic sedimentary section. Each sandstone has particular characteristics which can be related to the depositional setting. Reservoir quality is best developed in dominantly medium grained, moderate to well sorted sandstones, deposited as detached, basin floor submarine fan sands or interbedded turbidites. In contrast, reservoir quality is poorly developed in the remaining sand-prone facies deposited as slope fans, slumps, or distal turbidites.
8
Hasan, Ozren, Natalia Smrkulj, Slobodan Miko, Dea Brunović, Nikolina Ilijanić e Martina Šparica Miko. "Integrated Reconstruction of Late Quaternary Geomorphology and Sediment Dynamics of Prokljan Lake and Krka River Estuary, Croatia". Remote Sensing 15, n.º 10 (16 de maio de 2023): 2588. http://dx.doi.org/10.3390/rs15102588.
Resumo:
The upper part of the Krka River estuary and Prokljan Lake are a specific example of a well-stratified estuarine environment in a submerged river canyon. Here, we reconstructed the geomorphological evolution of the area and classified the data gathered in the study, integrating multibeam echosounder data, backscatter echosounder data, side-scan sonar morpho-bathymetric surveys, and acoustic sub-bottom profiling, with the addition of ground-truthing and sediment analyses. This led to the successful classification of the bottom sediments using the object-based image analysis method. Additional inputs to the multibeam echosounder data improved the segmentation of the seafloor classification, geology, and morphology of the surveyed area. This study uncovered and precisely defined distinct geomorphological features, specifically submerged tufa barriers and carbonate mounds active during the Holocene warm periods, analogous to recent tufa barriers that still exist and grow in the upstream part of the Krka River. Fine-grained sediments, classified as estuarine sediments, hold more organic carbon than coarse-grained sediments sampled on barriers. A good correlation of organic carbon with silt sediments allowed the construction of a prediction map for marine sedimentary carbon in this estuarine/lake environment using multibeam echosounder data. Our findings highlight the importance of additional inputs to multibeam echosounder data to achieve the most accurate results.
9
Gowans, Shannon, Hal Whitehead, Jakobina K. Arch e Sascha K. Hooker. "Population size and residency patterns of northern bottlenose whales (Hyperoodon ampullatus) using the Gully, Nova Scotia". J. Cetacean Res. Manage. 2, n.º 3 (31 de maio de 2023): 201–10. http://dx.doi.org/10.47536/jcrm.v2i3.908.
Resumo:
A population of northern bottlenose whales (Hyperoodon ampullatus) uses the Gully, a submarine canyon off the coast of Nova Scotia, Canada. Eleven years of photo-identification records has permitted estimation of population size using mark-recapture techniques. The population estimate was small (133 individuals, 95% CI = 111-166 from left side identifications; 127 individuals, 95% CI = 106-160 from right side identifications). The population was not closed, with the combined mortality, mark change and emigration rate estimated at 13% per year for left side identifications (95% CI = 9-17) and 14% for right side identifications (95% CI = 10-18). There was no significant increase or decrease in the population size between 1988-1999 (change in population size: left side: –0.13% per year, 95% CI = -3.4 to 3.9; right side: –0.43% per year, 95% CI = -4.5 to 3.1). The sex ratio was roughly 1:1, with equal numbers of sub-adult and mature males. Over the summer field season, individuals emigrated from, and re-immigrated into the Gully, spending an average of 20 days within the Gully before leaving (left side identifications 19 days, SE = 17; right side identifications 23 days, SE = 10). Approximately 34% of the population was present in the Gully at any time. Individuals of all age and sex classes displayed similar residency patterns although there were annual differences as individuals spent less time in the Gully in 1996 than in 1990 and 1997. Sighting rates were similar in all years with extensive fieldwork, indicating little variability in the number of whales in the Gully each summer. Accurate estimates of population size and residency patterns will be useful in determining the regulations and required coverage for a marine protected area in the Gully.
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Theodor, Marc, Gerhard Schmiedl, Frans Jorissen e Andreas Mackensen. "Stable carbon isotope gradients in benthic foraminifera as proxy for organic carbon fluxes in the Mediterranean Sea". Biogeosciences 13, n.º 23 (30 de novembro de 2016): 6385–404. http://dx.doi.org/10.5194/bg-13-6385-2016.
Resumo:
Abstract. We have determined stable carbon isotope ratios of epifaunal and shallow infaunal benthic foraminifera in the Mediterranean Sea to relate the inferred gradient of pore water δ13CDIC to varying trophic conditions. This is a prerequisite for developing this difference into a potential transfer function for organic matter flux rates. The data set is based on samples retrieved from a well-defined bathymetric range (400–1500 m water depth) of sub-basins in the western, central, and eastern Mediterranean Sea. Regional contrasts in organic matter fluxes and associated δ13CDIC of pore water are recorded by the δ13C difference (Δδ13CUmed-Epi) between the shallow infaunal Uvigerina mediterranea and epifaunal species (Planulina ariminensis, Cibicidoides pachydermus, Cibicides lobatulus). Within epifaunal taxa, the highest δ13C values are recorded for P. ariminensis, providing the best indicator for bottom water δ13CDIC. In contrast, C. pachydermus reveals minor pore water effects at the more eutrophic sites. Because of ontogenetic trends in the δ13C signal of U. mediterranea of up to 1.04 ‰, only tests larger than 600 µm were used for the development of the transfer function. The recorded differences in the δ13C values of U. mediterranea and epifaunal taxa (Δδ13CUmed-Epi) range from −0.46 to −2.13 ‰, with generally higher offsets at more eutrophic sites. The measured δ13C differences are related to site-specific differences in microhabitat, depth of the principal sedimentary redox boundary, and TOC content of the ambient sediment. The Δδ13CUmed-Epi values reveal a consistent relation to Corg fluxes estimated from satellite-derived surface water primary production in open-marine settings of the Alboran Sea, Mallorca Channel, Strait of Sicily, and southern Aegean Sea. In contrast, Δδ13CUmed-Epi values in areas affected by intense resuspension and riverine organic matter sources of the northern to central Aegean Sea and the canyon systems of the Gulf of Lion suggest higher Corg fluxes compared to the values based on recent primary production. Taking regional biases and uncertainties into account, we establish a first Δδ13CUmed-Epi-based transfer function for Corg fluxes for the Mediterranean Sea.
11
Molyneux, Stephen, Jeff Goodall, Roisin McGee, George Mills e Birgitta Hartung-Kagi. "Observations on the Lower Triassic petroleum prospectivity of the offshore Carnarvon and Roebuck basins". APPEA Journal 56, n.º 1 (2016): 173. http://dx.doi.org/10.1071/aj15014.
Resumo:
Why are the only commercial hydrocarbon discoveries in Lower Triassic and Permian sediments of the western margin of Australia restricted to the Perth Basin and the Petrel Sub-basin? Recent regional analysis by Carnarvon Petroleum has sought to address some key questions about the Lower Triassic Locker Shale and Upper Permian Chinty and Kennedy formations petroleum systems along the shallow water margin of the Carnarvon and offshore Canning (Roebuck/Bedout) basins. This paper aims to address the following questions:Source: Is there evidence in the wells drilled to date of a working petroleum system tied to the Locker Shale or other pre-Jurassic source rocks? Reservoir: What is the palaeogeography and sedimentology of the stratigraphic units and what are the implications for the petroleum systems?The authors believed that a fresh look at the Lower Triassic to Upper Permian petroleum prospectivity of the North West Shelf would be beneficial, and key observations arising from the regional study undertaken are highlighted:Few wells along a 2,000 km area have drilled into Lower Triassic Locker Shale or older stratigraphy. Several of these wells have been geochemically and isotopically typed to potentially non Jurassic source rocks. The basal Triassic Hovea Member of the Kockatea Shale in the Perth Basin is a proven commercial oil source rock and a Hovea Member Equivalent has been identified through palynology and a distinctive sapropelic/algal kerogen facies in nearly 16 wells that penetrate the full Lower Triassic interval on the North West Shelf. Samples from the Upper Permian, the Hovea Member Equivalent and the Locker Shale have been analysed isotopically indicating –28, –34 and –30 delta C13 averages, respectively. Lower Triassic and Upper Permian reservoirs are often high net to gross sands with up to 1,000 mD permeability and around 20% porosity. Depositional processes are varied, from Locker Shale submarine canyon systems to a mixed carbonate clastic marine coastline/shelf of the Upper Permian Chinty and Kennedy formations.
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Whiteway, Tanya, Andrew Heap, Tara Anderson e Rachel Przeslawski. "Marine mapping survey reveals broad-scale seabed environments of remote offshore basins in Western Australia". APPEA Journal 50, n.º 2 (2010): 730. http://dx.doi.org/10.1071/aj09094.
Resumo:
Between October 2008 and January 2009, Geoscience Australia conducted a marine mapping survey to document the seabed environments and subsurface geology of the Zeewyck, Houtman, Exmouth sub-basins and the deep-water Wallaby (Cuvier) Plateau, Western Australia. The seabed mapping survey, the second and largest mapping survey of the Federal Government’s Offshore Energy Security Program, documented seabed environments and biota from multibeam sonar and sub-bottom profiler data, towed video footage and physical samples. Preliminary analysis of the data indicates that for all of the sub-basins the seabed is comprised of carbonate mud that supports relatively sparse infaunal populations. Rocky substrates, principally in the numerous submarine canyons, supported sparse communities of sessile organisms. Interestingly, some of these hard-grounds were associated with volcanic (basaltic) peaks on the upper slope that attain 200 metres above the surrounding seabed. Data collected from the survey are being analysed in conjunction with existing environmental data to establish a series of environmental summaries that describe the key seabed habitats and biota for the offshore basins. The environmental summaries are being made available to support future acreage release in the sub-basins. The marine mapping survey was run in combination with a regional 2D seismic survey of the same offshore basins, also completed as part of the Offshore Energy Security Program.
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Kao, S. J., R. G. Hilton, K. Selvaraj, M. Dai, F. Zehetner, J. C. Huang, S. C. Hsu et al. "Preservation of terrestrial organic carbon in marine sediments offshore Taiwan: mountain building and atmospheric carbon dioxide sequestration". Earth Surface Dynamics 2, n.º 1 (4 de março de 2014): 127–39. http://dx.doi.org/10.5194/esurf-2-127-2014.
Resumo:
Abstract. Geological sequestration of atmospheric carbon dioxide (CO2) can be achieved by the erosion of organic carbon (OC) from the terrestrial biosphere and its burial in long-lived marine sediments. Rivers on mountain islands of Oceania in the western Pacific have very high rates of OC export to the ocean, yet its preservation offshore remains poorly constrained. Here we use the OC content (Corg, %), radiocarbon (Δ 14Corg) and stable isotope (δ13Corg) composition of sediments offshore Taiwan to assess the fate of terrestrial OC, using surface, sub-surface and Holocene sediments. We account for rock-derived OC to assess the preservation of OC eroded from the terrestrial biosphere and the associated CO2 sink during flood discharges (hyperpycnal river plumes) and when river inputs are dispersed more widely (hypopycnal). The Corg, Δ14Corg and δ 13Corg of marine sediment traps and cores indicate that during flood discharges, terrestrial OC can be transferred efficiently down submarine canyons to the deep ocean and accumulates offshore with little evidence for terrestrial OC loss. In marine sediments fed by dispersive river inputs, the Corg, Δ14Corg and δ 13Corg are consistent with mixing of terrestrial OC with marine OC and suggest that efficient preservation of terrestrial OC (>70%) is also associated with hypopycnal delivery. Sub-surface and Holocene sediments indicate that this preservation is long-lived on millennial timescales. Re-burial of rock-derived OC is pervasive. Our findings from Taiwan suggest that erosion and offshore burial of OC from the terrestrial biosphere may sequester >8 TgC yr−1 across Oceania, a significant geological CO2 sink which requires better constraint. We postulate that mountain islands of Oceania provide a strong link between tectonic uplift and the carbon cycle, one moderated by the climatic variability which controls terrestrial OC delivery to the ocean.
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Ross, Andrew, Alan Williams, Asrar Talukder, Joanna Parr, Christine Trefry, Richard Kempton, Charlotte Stalvies et al. "Building the regional understanding of the deep-water geology and benthic ecology of the Great Australian Bight". APPEA Journal 57, n.º 2 (2017): 798. http://dx.doi.org/10.1071/aj16212.
Resumo:
The Great Australian Bight (GAB) represents one of Australia’s most prospective frontier hydrocarbon exploration regions. Its largest subregion – the Ceduna sub-basin – is a deep (slope to abyss) area of 126 300 km2 with a 15-km deep sedimentary sequence that remains effectively untested. Knowledge of the Ceduna sub-basin’s geology is rapidly evolving following recent collection of 3D seismic datasets, but many questions remain about its geological evolution. The composition of the seabed biota and its ecology in the deep GAB was virtually unknown. To address a range of geological and biological questions, the multidisciplinary Great Australian Bight Deepwater Marine Program aims to build a more comprehensive regional understanding of the geology of the deep (~700–5437 m) GAB, with a focus on rocky outcrops, segif and volcanic seamounts, and to document aspects of the biota and benthic ecology for the first time. A field campaign of 63 days in 2015 aboard the RV Investigator and a second support vessel for an Autonomous Underwater Vehicle completed a detailed mapping of 10 225 km2 of seabed. In addition, physical geological and biological sampling collected 1.3 tonnes of volcanic and sedimentary rocks and over 25 553 biological specimens. A surprisingly complex deep-water sedimentary environment was revealed, including several previously unmapped deep-water canyons and 10 previously unmapped volcanic seamounts. A total of 430 species were collected, of which nearly half appeared to be unknown to science. This paper uses results from this survey to provide insights into the geological processes that have shaped the GAB, and briefly describes the makeup of biological assemblages present on the seabed.
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Obone-Zue-Obame, Edda Marlène, Virginie Gaullier, Françoise Sage, Agnès Maillard, Johanna Lofi, Bruno Vendeville, Isabelle Thinon e Jean-Pierre Rehault. "The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the “MAURESC” cruise". Bulletin de la Société Géologique de France 182, n.º 2 (1 de março de 2011): 181–96. http://dx.doi.org/10.2113/gssgfbull.182.2.181.
Resumo:
Abstract The Messinian salinity crisis (MSC) is characterized by gigantic erosion that remodels the margins while a thick, essentially evaporitic and detrital, sedimentary sequence forms in the deep basins. Based on recent (MAURESC, 2003) and earlier (MESEA 1, 1990; MAGIRAA, 1996; GEOBREST, 2002) seismic reflection data, this work brings to light the record of the MSC on the Provençal margin, which has until now been rarely explored from this perspective. Beyond its strictly regional interest, this study fits into a larger synthesis of MSC seismic markers in the Mediterranean and Black Sea marine domain [Lofi et al., 2011] and employs the new nomenclature established on this occasion. The results obtained reveal a Messinian detrital body (CU unit) of 625 metres maximum thickness at the foot of the margin, accumulating at the mouths of the principal canyons. Its form, facies and extension assimilate it to clastic fans, fed by subaerial erosion linked to the MSC. The relative geometry of CU and the Messinian units MU and UU deposited in the deep basin give indications to their chronostratigraphic relations. The deposition of the CU unit is posterior to the basal part of the mobile unit consisting of halite (MU), but contemporary to its top. These results agree with the recent scenarii, which propose that the precipitation of MU in the basin began early, during the lowering of the sea level, and ended at a low level during the MSC [Blanc, 2000; Martin et al., 2001; Sage et al., 2005; Ryan, 2009]. The UU unit surmounts MU and is subdivided into two sub-units with perceptibly different seismic facies : UU1 at the base and UU2 at the summit. UU1 could correspond to a unit containing more halite and/or more clastic material than UU2. The UU1 sub-unit could be partially contemporary to the CU unit. Concerning salt tectonics and its markers, three structural provinces have been evidenced in the sector of study, respectively : an upslope domain in extension (normal faults), an intermediary domain in translation (tabular MU) and a downslope domain in contraction (salt diapirs). These domains are directly linked to the gravity spreading and/or gliding of the brittle sedimentary cover formed by the CU, UU and Plio-Quatenary units and of the mobile level, MU. In the study area, a close relation between the distribution and thickness of CU and salt tectonics has additionally been evidenced at the mouths of the large Messinian canyons, being best expressed where CU is thick.
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Peybernès, Bernard, Marie-José Fondecave-Wallez e Pierre-Jean Combes. "Evidences of Palaeocene marine breccias unconformably overlying the Cretaceous orogenic axis of the Pyrenees, between Garonne and Gave de Pau". Bulletin de la Société Géologique de France 173, n.º 6 (1 de novembro de 2002): 523–32. http://dx.doi.org/10.2113/173.6.523.
Resumo:
Abstract Recently, have been evidenced in central/eastern French Pyrenees sub-marine polygenic breccias (Comus/Baixas Breccias), assigned to Upper Danian-Lower Selandian (P1c-P3) by means of planktonic foraminifera found either within their matrix, or within associated microrhythmic hemipelagites. These ante-Upper Eocene breccias, which are posterior to the HT-LP « Pyrenean » metamorphism (Mid.-Cretaceous in age and characterized by dipyre-bearing marbles and hornfelses) and to the Upper to Uppermost Cretaceous foldings, are only restricted to the Cretaceous orogenic axis of the range [Internal Metamorphic Zone (IMZ) and North-Pyrenean Zone (NPZ)]. They are dated in about 20 layers known from Mediterranean coast to Garonne valley. The breccias define in this part of Pyrenees a wide and long (more than 200 km) W-E trough (subdivided into several meridian palaeocanyons) inherited from former karstic topographies and separated by mountains with a steep topography, flanked to the South and the North of continental areas (covered by « Vitrollian » fluvio-lacustrine deposits). It was important to evidence if this marine breccia-filled « trough », Palaeocene in age, could extend westwards, West of Garonne, in Comminges/Barousse and Bigorre, where, laterally, the « Vitrollian » continental areas are replaced by outer-shelf marine sediments (clinoform carbonates), both covering the Sub-Pyrenean Zone (SPZ) and the High Primary Range (HPR) (Gavarnie-Mont-Perdu thrust sheet). In fact, the presence of those breccias has been already suggested (but without micropalaeontologic arguments) by Mattauer [in Choukroune, 1969 and 1976] in the Lourdes area (Bigorre). The topic of this paper is to characterize and to assign to the lower part of Palaeocene (63-59 Ma interval) several significant outcrops (St-Béat, Bramevaque/Troubat/Gembrié, Lortet, Medous/Bagnères-de-Bigorre and Lourdes/Pibeste) of these marine breccias (some of them previously used as black/yellow marbles called « Brèche romaine de St-Béat », « Portor des Pyrénées » or « Marbres de Medous ») recently identified from Garonne to Gave-de-Pau (fig. 1). Although quite poor in argillaceous hemipelagites, most of the breccias (which contain Mesozoic clasts) are now well dated by sections of « globigerinids » (= superfamily of Globerinacea) observed within their matrix. Other marine Palaeocene breccias also exist, more to the South (col de Gembre) along segments of the North-Pyrenean Fault, but they only rework Palaeozoic clasts. The « globigerinid » assemblage checked within all the Palaeocene breccias of Comminges/Bigorre includes, as more to the east, the following taxa: Globanomalina compressa, Gl. ehrenbergi, Gl. imitata, Parasubbotina varianta, P. variospira, Igorina pusilla, Morozovella angulata, M. praeangulata, Praemurica spiralis, Pr. inconstans and Woodringina hornestownensis. This assemblage is also laterally present within the marine carbonate sequences of the SPZ – HCR cover (« Lasseube Limestones » from the Nay/Pont Labau area, « Globigerinid-bearing Limestones » from the Gavarnie-Mont-Perdu thrust sheet), regions which are peripheric to the Pyrenean Lower/Mid. Cretaceous orogen (IMZ, NPZ) because exempt of major angular unconformity between Maastrichtian and Danian marine deposits (only a short gap of Lower/Lowermost Danian underlines the K/T boundary). On the contrary, the herein studied regions, belonging to this orogen, are characterized by a clear unconformity (both angular and cartographic) along a well-marked ravining surface inherited from erosional processes and karstification. The substratum of these breccias is strongly folded, cleaved and sometimes metamorphic and its younger formation seems to be Mid.– Cretaceous in age at least. Thus, it is very probable that the ante-Palaeocene unconformity seals compressional/transpressional structures (followed by emersions) assigned to the Uppermost Cretaceous phase (palinspastic transect, fig. 5). Danian/Selandian marine breccias and their already folded Mesozoic substratum are later tectonically reactived together by the « Pyrenean » compressions, Upper Eocene in age. If the elements of these breccias sometimes correspond to marbles induced by the Mid.-Cretaceous thermometamorphism (as around the famous « Etang de Lherz », more to the East, where lherzolites are also reworked in similar Danian/Selandian breccias), their matrix locally contain neogenic phyllites (never dipyre !) which could be related to a light (hydrothermal ?) post-breccia metamorphism. The clasts are generally angular, showing a very short transport from emerged steep topographies separating the different elementary canyons of the trough. The last problem is to determine the eventual westwards extension in the Bearn and Basque Pyrenees (fig. 6), particularly in the « Chaînons Béarnais » Zone which belonged to the North-Iberian palaeomargin (Iberian Plate) of the future range during Lower/Mid.-Cretaceous times. At this first level of micropalaeontologic investigations, it seems that several breccias (Lauriolle, Etchebar, Bosmendiette etc …), previously interpreted by several authors (synthesis in James and Canerot [1999]) as Aptian and « diapiric » (collapse) breccias, should be assigned to marine Palaeocene deposits because containing (in their matrix and associated hemipelagites) Danian-Selandian planktonic foraminifera similar to the Comminges/Bigorre ones.
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Buchan, Susannah J., Marcel Ramos, Jorge Oyanadel, Macarena Santos-Carvallo, Luis Bedriñana-Romano, María Valladares, Marinella Maldonado et al. "Understanding the oceanographic dynamics of the Isla Chañaral baleen whale feeding ground, (Humboldt Archipelago, Northern Chile) to extend habitat protection". Frontiers in Marine Science 10 (4 de janeiro de 2024). http://dx.doi.org/10.3389/fmars.2023.1208262.
Resumo:
Off Northern Chile, baleen whales use the area around Isla Chañaral as a feeding ground where they forage on euphausiids. Isla Chañaral is part of the highly productive Humboldt Archipelago (∼ 28°S-29°S) within the Humboldt Current System (HCS). In this study, we seek to understand the sub-mesoscale spatial distribution of fin and blue whales and their prey around Isla Chañaral using systematic and opportunistic visual sighting data of whales and systematic acoustic backscatter data of zooplankton from an Acoustic Zooplankton and Fish Profiler (AZFP); and to examine the oceanographic dynamics of the wider Humboldt Archipelago area with remote-sensing oceanographic data. We completed a total of 512.6 km of survey effort over 20 days in 2018 and 318.3 km over 16 days in 2019 collecting systematic whale sighting and backscatter data. A total of 42 fin whales, 0 blue whales and 66 unidentified whales were sighted in 2018, and 7 fin whales, 3 blue whales and 12 unidentified whales were sighted in 2019. Observed spatial distribution of backscatter and whales was strongly associated with a bathymetric feature, i.e., the submarine canyon that curves around Isla Chañaral. Generalized Additive Models showed that fin whale presence was associated with high levels of backscatter and shallow depths similar to those of the canyon. We found that long-term average geostrophic currents form a recirculation system between 28°S and 31°S that can transport nutrient-rich upwelled surface waters back towards the Humboldt Archipelago and contribute to high biological productivity in this area. However, in summer 2019 geostrophic flow occurred away from the coast and a warm low-productivity spring explained low backscatter and whale sightings around Isla Chañaral. The unique oceanographic features of Isla Chañaral and the Humboldt Archipelago that contribute to high concentrations of Endangered baleen whales and their prey justify the extension of the Isla Chañaral Marine Reserve to include the canyon between the mainland and the island, and the implementation of a Multiple Use Marine Protected Area for the entire Humboldt Archipelago area that explicitly protects this critical feature.
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Holland, Robert D., Thomas S. Coolbaugh e Paul Schuler. "Bridging research to response – how the spill response community benefits from academic engagement". International Oil Spill Conference Proceedings 2021, n.º 1 (1 de maio de 2021). http://dx.doi.org/10.7901/2169-3358-2021.1.684986.
Resumo:
ABSTRACT Often technical advances are made through key industry-academic alliances in a diverse range of engineering, medical and scientific disciplines. Oil spill response studies are no stranger to research programmes within the academic / R&D community and have advanced our knowledge, understanding and capability significantly over the last 50 years. For example, following the use of industrial detergents during Torrey Canyon in 1967, the research, development and scientific rigour behind the latest marine dispersants is testament to the value in investment of resources to develop and deliver solutions to new and emerging risks. Typically, spill responders are focussed on operational issues and seeking maximum reward when selecting a response technique(s) as part of a given spill scenario. Research scientists conversely may be focussed on a more detailed aspect of the spill such as a sub-cellular, non-lethal biological effect which may have limited relevance to the immediate clean-up effort. Having a spill response organisation intrinsically involved with academic response research ensures that an element of “operational realism” is injected into the programmes to produce outputs with more direct relevance and application to advance the boundaries of future spill response techniques and capability. The paper discusses the merits and leverage potential of “Bridging Research to Response” and offers suggestions for future collaborations potentially adding value to all spill stakeholders.
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Hambrey, Michael J., e Anthony M. Spencer. "Late Precambrian glaciation of central East Greenland". Meddelelser om Grønland. Geoscience 19 (13 de agosto de 1987). http://dx.doi.org/10.7146/moggeosci.v19i.138868.
Resumo:
The Vendian succession of the central East Greenland fjord region is among the best preserved and most extensively exposed in the world and is represented approximately by the Tillite Group, comprising five formations, which from bottom to top are: the Ulvesø Formation (formerly Lower Tillite, dominantly diamictite), the Arena Formation (formerly Inter-Tillite beds, dominantly sandstone and shale), the Storeelv Formation (formerly Upper Tillite, dominantly diamictite, sandstone and conglomerate), the Canyon Formation (dominantly shale and dolostone) and the Spiral Creek Formation (dominantly sandstone, shale and dolostone). The group is underlain by Bed group 20 (limestone) and Bed group 19 (dominantly carbonate, shale and breccia) in different places and in the peripheral areas by older Bed groups of the Eleonore Bay Group. Above, the transgressive Cambrian sandstones of the Kløftelv Formation cap the Vendian sequence, though the exact level of the Precarmbrian-Cambrian boundary may be slightly lower. This paper reviews previous work on the succession and presents numerous new stratigraphic sections and an assessment of the sedimentary structures. The stratigraphic and palaeoenvironmental significance of the succession can therefore be assessed. Both main diamictite horizons contain other facies, which together with sedimentary structural and fabric data indicate that the following sediments have been produced: lodgement tillites, waterlain tillites, proximal and distal glaciomarine sediments (with ice-rafted dropstones), glaciolacustrine sediments, fluvioglacial deposits, subaqueous and sub-aerial mass-flows and periglacial phenomena. The other sediments of the Tillite Group were deposited in a dominantly shallow marine or lacustrine environment. Deeper water turbidites are recorded in part of the Arena Formation, whilst the upper part of the group indicates periodic emergence. Stromatolites, desiccation cracks and halite pseudomorphs are particularly distinctive in this part of the succession. A hiatus preceded deposition of the Kløftelv Formation, a transgressive unit of tidally-influenced sandstones. Stratigraphic thicknesses vary considerably, and whereas individual formations can be recognised throughout most of the fjord region, intraformational horizons cannot normally be traced for more than several kilometres. The nature of the bottom contact of the Tillite Group remains enigmatic, and transitional sedimentary, unconformable and thrust contacts are all present. It is possible that Bed Group 20 may be the lateral equivalent of the Ulves0 Formation, or of Bed Group 19. Although local palaeogeography was complex during deposition of the diamictites, these rocks indicate that a low-level ice sheet prevailed at the time. Together with Svalbard and western Scotland they represent the periphery of an ice-sheet which stretched across much of northern Europe to the Urals. However, much of Vendian time was not characterised by glacial conditions, and warm climates prevailed when the upper part of the Tillite Group was deposited.
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Yadav, Ravi, e A. S. Maurya. "A freshwater ostracod assemblage from the Kesavi intertrappean beds (latest Cretaceous/earliest Paleocene) of lower Narmada Valley, Malwa Sub-province of Deccan Traps, Dhar District, Madhya Pradesh, India". Journal of the Palaeontological Society of India, 23 de setembro de 2023. http://dx.doi.org/10.1177/05529360231181799.
Resumo:
We here report a new freshwater ostracod assemblage comprising 11 species ( Frambocythere tumiensis anjarensis, Gomphocythere paucisulcatus, G. strangulata, Limnocythere deccanensis, Zonocypris spirula, Eucypris intervolcanus, Cypria cyrtonidion, Stenocypris cylindrical, Cypridopsis hyperectyphos, Candona amosi, Eucypris sp.) from a newly discovered intertrappean locality at Kesavi, Dhar District, Madhya Pradesh. This locality lies in the lower Narmada Valley of Malwa sub-province, a poorly studied region of the Deccan Traps volcanic province of peninsular India compared to the other volcanic sub-provinces. The ostracod assemblage from Kesavi is similar to those known from different parts of the Deccan volcanic province and lacks any brackish or marine elements. The endobenthic crawler Frambocythere tumiensis dominates the assemblage, indicating a lacustrine freshwater depositional environment.
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Hurtado-García, Jennifer, e M. Eugenia Manjón-Cabeza. "Species composition of sea stars (Echinodermata: Asteroidea) in the Patagonian Argentinian deep sea, including seven new records: connectivity with sub-Antarctic and Antarctic fauna". Polar Biology, 28 de junho de 2022. http://dx.doi.org/10.1007/s00300-022-03056-x.
Resumo:
AbstractThe main target of this paper is to improve the knowledge of the species composition of sea stars in Patagonian Argentine deep sea reaching depths of 2062 m. In addition, these results offer us the opportunity to analyze the possible connections between Argentinian marine fauna and adjacent Antarctic areas that have become a topic of interest in the past few years. This work is based on Atlantic Projects’ surveys carried out on an atypical and especially vulnerable marine ecosystems (canyons created from craters collapse by gas leaks). These are profusely impacted by frequent fishing activities, being one of the most important and international fishing grounds, where 887 records (1878 specimens) of 41 species of asteroids were collected in 217 stations ranging from 219 to 2062 m in depth. Seven of those species are proposed as new records: (Diplasterias octoradiata (Studer 1885), Plutonaster bifrons (Wyville Thomson, 1873), Radiaster elegans Perrier, 1881, Anseropoda antarctica Fisher, 1940, Pillsburiaster calvus Mah, 2011, Paralophaster lorioli (Koehler, 1907), Pteraster flabellifer Mortensen 1933). After refining the database built from literature and open-access databases such as OBIS and AntBIF, the new Argentinian asteroids deep-water checklist contains 2198 records from 64 asteroids species including the 7 new records proposed. Most of these 64 species (89.06%) are present in Antarctic-adjacent waters, and after the study of their occurrences at traditional biogeographic entities, our results support the hypothesis that Argentinian waters (in the case of the class Asteroidea) should be considered part of the sub-Antarctic entity.