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1
Wang, H., e X. Jia. "Selective deposition response to aeolian-fluvial sediment supply in the desert braided channel of the Upper Yellow River, China". Natural Hazards and Earth System Sciences Discussions 3, n. 2 (10 febbraio 2015): 1269–90. http://dx.doi.org/10.5194/nhessd-3-1269-2015.
Testo completoAbstract (sommario):
Abstract. Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such a cross-dune braided river. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. This selective deposition developed by the interaction between the flows and the Aeolian-fluvial sediment supplies, making the coarser sediments (> 0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel center and the finer fluvial sediments (< 0.08 mm) to be deposited on the bar and floodplain surfaces and forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of "above-ground river" in the braided reach of the Upper Yellow River in response to aeolian and fluvial sediment supplies.
2
Wang, H., X. Jia, Y. Li e W. Peng. "Selective deposition response to aeolian–fluvial sediment supply in the desert braided channel of the upper Yellow River, China". Natural Hazards and Earth System Sciences 15, n. 9 (2 settembre 2015): 1955–62. http://dx.doi.org/10.5194/nhess-15-1955-2015.
Testo completoAbstract (sommario):
Abstract. Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such cross-dune braided rivers. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. The Ulan Buh desert is the main coarse sediment source for this desert braided channel, and the mean percentage of the coarser (> 0.08 mm) grains on the aeolian dunes surface is 95.34 %. The lateral selective deposition process is developed by the interaction between the flows and the aeolian–fluvial sediment supplies, causing the coarser sediments (> 0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel centre and the finer fluvial sediments (< 0.08 mm) to be deposited on the bar and floodplain surfaces, forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of an "above-ground" river in the braided reach of the upper Yellow River in response to aeolian and fluvial sediment supplies.
3
Sigdel, Ashok, e Tetsuya Sakai. "Sedimentary facies analysis of the fluvial systems in the Siwalik Group, Karnali River section, Nepal Himalaya, and their significance for understanding the paleoclimate and Himalayan tectonics". Journal of Nepal Geological Society 51 (31 dicembre 2016): 11–26. http://dx.doi.org/10.3126/jngs.v51i0.24084.
Testo completoAbstract (sommario):
Fluvial sediments of the Siwalik successions in the Himalayan Foreland Basin are one of the most important continental archives for the history of Himalayan tectonics and climate change during the Miocene Period. This study reanalyzes the fluvial facies of the Siwalik Group along the Karnali River, where the large paleo-Karnali River system is presumed to have flowed. The reinterpreted fluvial system comprises fine-grained meandering river (FA1), flood-flow dominated meandering river with intermittent appearance of braided rivers (FA2), deep and shallow sandy braided rivers (FA3, FA4) to gravelly braided river (FA5) and finally debris-flow dominated braided river (FA6) facies associations, in ascending order. Previous work identified sandy flood-flow dominated meandering and anastomosed systems, but this study reinterprets these systems as a flood-flow dominated meandering river system with intermittent appearance of braided rivers, and a shallow sandy braided system, respectively. The order of the appearance of fluvial depositional systems in the Karnali River section is similar to those of other Siwalik sections, but the timing of the fluvial facies changes differs. The earlier appearance (3-4 Ma) of the flood-flow dominated meandering river system in the Karnali River section at about 13.5 Ma may have been due to early uplift of the larger catchment size of the paleo-Karnali River which may have changed the precipitation pattern i.e. intensification of the Indian Summer Monsoon. The change from a meandering river system to a braided river system is also recorded 1 to 3 Ma earlier than in other Siwalik sections in Nepal. Differential and diachronous activities of the thrust systems could be linked to change in catchment area as well as diachronous uplift and climate, the combination of which are major probable causes of this diachronity.
4
Lu, Zhiyuan, Zhiliang He, Shizhong Ma e Yu He. "Sedimentary characteristics and sand-body distributions in the Lower Permian He 8 Member, Ordos Basin, China". Interpretation 10, n. 2 (22 febbraio 2022): T223—T236. http://dx.doi.org/10.1190/int-2021-0101.1.
Testo completoAbstract (sommario):
The Lower Permian He 8 Member (P1h8) in the Ordos Basin is a typical producing zone of tight lithologic gas reservoirs. Analyses of sedimentary characteristics, electrofacies, and sand-body distributions of P1h8, conducted on modern fluvial deposits, outcrops, cores, and well logs, revealed that braided rivers that developed in the Lower P1h8 and Upper P1h8 are characterized by meandering river. Within these fluvial deposits, the procedure consists of analyzing high-resolution sequence stratigraphy and sedimentary dynamics defined from calibrated logging curve signatures and depositional studies. According to modern and ancient fluvial deposits, we have developed a process-based sedimentary conceptual model for interpreting and predicting the distribution and geometries of sand bodies in braided and meandering deposits. The main sand body of the braided river system was bars and channel fill deposits. The braided river sand bodies are distributed over multiple vertical superimpositions and overlapping horizontal connections. The meandering river sand bodies are mainly point-bar deposits, which are bead-shaped and exhibit scattered development in the vertical direction. This comparison indicates that there were significant differences between braided and meandering deposystems. The sand bodies in the Lower P1h8 were multidirectionally connected and primarily distributed in a stacked pattern. In contrast, the sand bodies in the Upper P1h8 were distributed in an isolated manner, and fine grains (mud and silt) were deposited between the sand bodies with poor connectivity. We interpreted the fluvial deposits that control the distributions of the sand body of the He8 Member in the eastern Sulige gas field and constructed a corresponding prediction model of a braided-meandering reservoir. This model will promote understanding of the extent of fluvial deposits and sand-body distribution of P1h8, thus elucidating hydrocarbon-bearing sand units of the Ordos Basin for future exploration.
5
Ju, Xiaoyu, Xiaodong Zhao, Boyu Zhou, Ruixue Zhang, Xinyu Wu e Dafa Guo. "Identification of Reservoir Water-Flooding Degrees via Core Sizes Based on a Drip Experiment of the Zhenwu Area in Gaoyou Sag, China". Energies 16, n. 2 (4 gennaio 2023): 608. http://dx.doi.org/10.3390/en16020608.
Testo completoAbstract (sommario):
In order to identify the degree of water flooding in a reservoir and to discover any remaining oil-enriched areas, in this paper, a systematic study on the water flooding of cores in obturated coring wells is carried out. With observations and testing data of the cores, based on the notion of sedimentary facies, the water-flooding degrees of 4–7 sand groups in member one of the Paleogene Sanduo Formation (E2s14–7) of the Zhenwu area in the Gaoyou Sag are determined. Overall, the results show that the study area is formed under the background of lake regression, with various sedimentary systems, mainly including delta facies, braided fluvial facies, and meandering fluvial facies. The degree of water flooding is determined using a point-by-point drip experiment of the core. Combined with the testing results of the core, the water-flooding degrees of the different sedimentary facies are quantitatively determined. Identification standards for the water-flooding degree of delta facies, braided river facies, and meandering river facies are established. The water-flooding degree of the delta sand body is generally weak, with an oil saturation rate of 24.1–40.2%, essentially indicating no water flooding or weak water flooding. The water-flooding degree of the braided fluvial sand body significantly changes, and the variation range of the oil and water saturation measurement results is also large. The water-flooding degree of the meandering fluvial sand body is weaker than that of the braided fluvial sand body, which is mostly not flooded or weakly flooded. The water-flooding degree is obviously controlled by the sedimentary rhythm and the sedimentary type. The top of the positive rhythm, the bottom of the sludge bed in the braided fluvial point bar, the deltaic front subaqueous distributary channel, and the point bar in the meandering fluvial have relatively low water-flooding degrees. They are the subjects of subsequent development adjustment and the remaining oil potential tapping.
6
Zawri, Nurul Fahana, Abdul Hadi Abd Rahman, Numair Ahmed Siddiqui e Norizam Md Nor. "Geomorphological evolution of the Group I fluvial system, AX field, Malay Basin". IOP Conference Series: Earth and Environmental Science 1003, n. 1 (1 aprile 2022): 012009. http://dx.doi.org/10.1088/1755-1315/1003/1/012009.
Testo completoAbstract (sommario):
Abstract The AX Field is located 167km off NNE Kerteh, Terengganu of Peninsular Malaysia, southwest of Malay Basin. This study is focused on the 3D seismic analysis of the Lower Miocene fluvio-deltaic Group I. The objective of the study is to evaluate the geomorphological evolution of fluvial succession and interpret the possible intra-basinal and extra-basinal controls on the fluvial evolution. One hundred strata slices were generated in order to evaluate the evolution of the fluvial systems within the Group I interval. Seismic attributes such as Root Mean Square (RMS), sweetness and spectral decomposition were computed to map channel geomorphology. Different fluvial styles were identified in the different parts of the study area. Variation of fluvial style were identified within the Group I interval including the low sinuosity system with tributary channels, high sinuosity system with broad meander belt and braided system. Fluvial channel imaged within the studied interval can be divided into six (6) stages based on the channel morphology. Stage 1 (1875 – 1810 ms), the oldest stage, displays high sinuosity channels. Braided system associated with coal deposition were imaged in Stage 2 (1810 – 1765 ms). During stage 3 (1765 – 1710 ms), the fluvial system is characterized by low to moderate sinuosity channel features that varies in scale and geometry. Stage 4 (1710 – 1675 ms) display fluvial style characterized by low sinuosity-to-straight system with tributary channels. Stage 5 (1675 – 1615 ms) is represented by high sinuosity fluvial system with broad meander belt and point bar. During Stage 6 (1615-1536 ms) the fluvial system displays moderate-to-high sinuosity. The high sinuosity system in period 6 exhibit well-defined meander scroll bar morphology that reveals the extension and translation course of the fluvial system.
7
Sun, Yu, Xiu Li Zhang, Jin Yan Zhang e Chen Chen. "Analysis on Grain-Size Characteristics and Sedimentary Environment of Conglomerate Reservoirs in Ying-4 Section of Xingcheng Gas Field of Songliao Basin". Advanced Materials Research 734-737 (agosto 2013): 286–89. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.286.
Testo completoAbstract (sommario):
Aimed at difficulty of conglomerate in Ying-4 Section of Xingcheng Gas Field, Songliao Basin, which it is impossible to be carried out, using routine granularity analysis methods, and the iconic grain-size analysis is carried out. According to iconic two-dimension grain-size analysis, and contacting to fundamental sedimentary characteristics of conglomerate, sedimentary environment analysis is carried out. It is thought that this area is Shallow gravel-bed braided fluvial fan deltas, to braided fluvial delta transition, which supported an important geological foundation for the next disposition of exploration in Xingcheng Gas Field.
8
Liu, Yuming, Luxing Dou, Xiaoxu Ren e Jiagen Hou. "Sedimentary characteristics of muddy deposits in sandy braided fluvial system: A case study from outcrops of the Jurassic Yungang Formation in the Datong Basin, Central China". Interpretation 8, n. 3 (1 luglio 2020): SM139—SM149. http://dx.doi.org/10.1190/int-2019-0174.1.
Testo completoAbstract (sommario):
The sandbodies within braided fluvial deposits are important reservoirs for the oil fields in China, and they usually have complex sedimentary architecture. A lot of research has been concentrated on characterizing the architecture of the sandbodies. Based on the observation that muddy deposits are commonly well preserved in fluvial deposits, we find that understanding the contact relationship between the muddy deposits and surrounding sand bodies can help characterize the depositional process of sandy braided fluvial systems. We have determined the effectiveness of this idea by characterizing a well-exposed outcrop of sandy braided fluvial system in the Datong Basin, Shanxi Province of China. We first define six muddy lithofacies by integrating the thickness of the muddy deposits, the morphology of the muddy deposit, and the lithofacies of surrounding sand deposits. The six muddy lithofacies include floodplain muddy deposits between intermittent channel complex, lateral covering muddy deposits and fall-silt seam muddy deposits between migrated bar complex, muddy gravel deposits in erosional bar complex, and channel-fill muddy deposits and gully-fill muddy deposits in abandoned bar complex. We then analyze the depositional environments according to the defined muddy lithofacies. We finally build the architecture of the outcrops by integrating the lithofacies of sand deposits and evolution of the depositional environments deduced from the muddy lithofacies.
9
Cui, Kunning. "Characteristics of sedimentary system evolution and sequence stratigraphy boundary of Denglouku group in Xujiaweizi fault depression, Songliao Basin". IOP Conference Series: Earth and Environmental Science 1087, n. 1 (1 ottobre 2022): 012073. http://dx.doi.org/10.1088/1755-1315/1087/1/012073.
Testo completoAbstract (sommario):
Abstract In the previous studies on this area, the sequence division is relatively rough. This study has improved the precision, and the Denglouku formation is divided into 10 fourth-order sequences, with the thickness of each small layer of about 70-80m. The characteristics of each small sequence boundary are described, and three third-order, four fourth-order sequence flooding surfaces are found. The stratigraphic framework is established. From bottom to top, the base level of all strata shows decline-rise-decline, which means regression-transformation-regression. The Denglouku 1st mainly includes lacustrine and fan delta, the sources of sediments from northeast, northwest, southwest and Southeast directions. In Denglouku 2nd and Denglouku 3rd, braided fluvial delta and intermittent lacustrine are dominant, which were controlled by the sedimentary systems from east, south, north, northeast, southwest, and the northwest. In Denglouku 4th, there is mainly braided fluvial, rarely are lacustrine and braided fluvial delta plain, the main source was from the northeast, and a small amount of source is from the west.
10
Candeiro, Carlos Roberto, Rodrigo Pinto De Azevedo e Priscila Maria Da Silva. "PRELIMINARY APPROACH ON DEPOSITIONAL ENVIRONMENTAL OF THE UBERABA FORMATION (UPPER CRETACEOUS), PEIRÓPOLIS SITE, MINAS GERAIS STATE, BRAZIL: AN INTRODUCTION". Caminhos de Geografia 8, n. 22 (22 settembre 2007): 81–85. http://dx.doi.org/10.14393/rcg82215625.
Testo completoAbstract (sommario):
The Coniacian-Santonian Uberaba Formation of Triângulo Mineiro region hás yielded a important paleofauna from fluvial and associated paleoenvironments. Although poor, fossil content are represented by invertebrates and vertebrates. The paleontological and geological data suggested that Uberaba Formation is characterized by a fluvial of a braided type.
11
Miall, Andrew D., e Mohamud Arush. "Cryptic sequence boundaries in braided fluvial successions". Sedimentology 48, n. 5 (21 ottobre 2001): 971–85. http://dx.doi.org/10.1046/j.1365-3091.2001.00404.x.
Testo completo
12
Kang, Qiangqiang, Jiagen Hou, Liqin Liu, Mingqiu Hou e Yuming Liu. "Quantitative Prediction of Braided Sandbodies Based on Probability Fusion and Multi-Point Geostatistics". Energies 16, n. 6 (17 marzo 2023): 2796. http://dx.doi.org/10.3390/en16062796.
Testo completoAbstract (sommario):
Predicting the spatial distribution of braided fluvial facies reservoirs is of paramount significance for oil and gas exploration and development. Given that seismic materials enjoy an advantage in dense spatial sampling, many methods have been proposed to predict the reservoir distribution based on different seismic attributes. Nevertheless, different seismic attributes have different sensitivities to the reservoirs, and informational redundancy between them makes it difficult to combine them effectively. Regarding reservoir modeling, multi-point geostatistics represents the distribution characteristics of the braided fluvial facies reservoirs effectively. Despite this, it is very difficult to build high-quality training images. Hence, this paper proposes a three-step method of predicting braided fluvial facies reservoirs based on probability fusion and multi-point geostatistics. Firstly, similar statistical data of modern sedimentation and field paleo-outcrops were processed under the guidance of the sedimentation pattern to construct reservoir training images suitable for the target stratum in the research area. Secondly, each linear combination of selected seismic attributes was demarcated to calculate the principal component value and work out the elementary conditional probability. Lastly, the PR probability integration approach was employed to combine all conditional probabilities and calculate the joint probability. Then the joint probability was combined with training images to build a reservoir distribution model through multi-point geostatistics. We illustrated the detailed workflow of our new method by applying it to a braided fluvial reservoir modeling case in the Bohai Bay Basin, East China. The new method reduced the error of prediction results by 32% and 46% respectively, and the error of water content by 36.5% and 60.3%. This method is a potentially effective technique to predict and characterize the reservoir spatial distribution and modeling in other oil fields with the same geological background.
13
Ulak, Prakash Das. "Evolution of fluvial system and reconstruction of paleohydrology of late Cenozoic Siwalik Group, related to tectonic uplift of Himalaya and climatic change, Kankai River section, east Nepal Himalaya". Journal of Nepal Geological Society 51 (31 dicembre 2016): 59–72. http://dx.doi.org/10.3126/jngs.v51i0.24093.
Testo completoAbstract (sommario):
This paper focuses on evolution of the fluvial system in the late Cenozoic Siwalik Group along the Kankai River section of East Nepal. The Siwalik Group lies on the southern flank of the Himalaya and composed of molasse sediments, which were derived from upheaval of the Himalaya. On the basis of lithology, assemblage of sedimentary structures and sediment body architectures, seven facies associations (FA1 to FA7) are recognized in the Kankai River section, East Nepal Himalaya. These recognized facies associations are closely related to each lithostratigraphic units of the area (Ulak 2009). The lower and upper members of the Lower Siwaliks are the products of the fine-grained meandering and flood flow-dominated meandering systems, respectively. The lower, middle and upper members of the Middle Siwaliks are interpreted as the deposits of the sandy meandering, deep sandy braided and shallow braided systems, respectively whereas the lower and upper members of the Upper Siwaliks are the products of the gravelly braided and debris flow-dominated braided systems, respectively. Paleohydrological characteristics and its evolutional changes of the group have been estimated by using grain diameter and thickness of fining upward fluvial successions. The paleohydrology suggests an increase in of flow velocity, channel slope gradient, and discharge of the fluvial system. Paleovelocity varies from 0.19 m/s to 5.31 m/s paleochannel gradient and paleodischarge changes from 6.67x10-5 to 2.97x10-4 m/m and 101 to 104 m3/s, respectively in stratigraphic upward. The progressively changes in the paleohydrology reflect the southward propagation of thrust activities, caused upheaval of the Himalaya.
14
Payenberg, T. H. D., e S. C. Lang. "RESERVOIR GEOMETRY OF FLUVIAL DISTRIBUTARY CHANNELS—IMPLICATIONS FOR NORTHWEST SHELF, AUSTRALIA, DELTAIC SUCCESSIONS". APPEA Journal 43, n. 1 (2003): 325. http://dx.doi.org/10.1071/aj02017.
Testo completoAbstract (sommario):
The exploration and development of stratigraphically trapped hydrocarbons requires detailed knowledge of the morphologies and reservoir characteristics of the stratigraphic body. Fluvial distributary channels are important exploration targets because they are typically isolated reservoirs, laterally and vertically sealed by delta plain and abandoned channel mudstone, and thus form excellent stratigraphic traps. The morphology and reservoir characteristics of fluvial distributary channels have been confused with fluvial channels in the past. Knowing the characteristics of fluvial distributary channels and their difference from fluvial channels is the key to the successful exploration and development of distributary channel reservoirs.Fluvial distributary channels, formed by mixed-load systems, are commonly rectilinear channel segments found only on the delta plain between the head of passes and the depositional mouthbars. While fluvial channel reservoirs are mainly sandstone deposits of meander pointbars or braided sheets, fluvial distributary channel reservoirs are typically elongated sandy channel sidebars attached to morphologically rectilinear channel walls. The sidebars form by both lateral and downstream accretion resulting from flow in a confined, but lowsinuosity thalweg, which may be filled with organic mud following channel abandonment. On 3D seismic data the morphology of a fluvial distributary channel is often slightly sinuous and can easily be mistaken for part of a meander channel belt.Fluvial distributary channels are usually thinner and shallower compared to their updip fluvial channel belts. Width-thickness ratios for fluvial distributary channel reservoirs are on average 50:1 (range 15:1 to 100:1), while meandering fluvial channel reservoirs have widththickness ratios typically >100:1, and braided river reservoirs show ratios of 500:1 or higher. Examples from the Mahakam Delta are used to illustrate these issues. Implications for exploration and development of deltaic deposits on the North West Shelf of Australia are discussed.
15
Fan, Er Ping, Yue Hong Cheng, Yuan Zhi Zhang e Zhen Hua Bai. "Sedimentology and Reservoir Characteristics of He8 Member, in a Gas Field of Ordos Basin, Northern China". Advanced Materials Research 734-737 (agosto 2013): 161–65. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.161.
Testo completoAbstract (sommario):
The rapid lateral variation of fluvial sand-bodies seriously affect the development of oil and gas field. One long-term base-level cycle (LSC), four middle-term base-level cycles (MSC) and nine short-term base level cycles (SSC) are recognized by researching the stacking patterns and volumetric partitioning according to the core, well log and seismic data in He8 member of A gas field, Ordos basin. The base level cycles which are mainly base level rise half cycles are mainly composed of braided and meandering river deposits. The evolution of depositional system has experienced three stages: braided river deposition in the earlier stage, braided and meandering river transition coexistence in the middle stage and only meandering river deposition in later period. The braided channel sand, mid-channel bar and point bar are mainly reservoirs which show belt and ribbon along the SEE trending. These sand-bodies are vertically and laterally stacked with good continuity in the early MSC1, MSC2 and MSC3, while isolated and with poor continutiy in the early MSC4. The sedimentary microfacies and diagenesis affect the fluvial reservoir quality including lateral continuity, porosity and permeability and the buried depth of the good reservoirs with development of secondary solution pores is less than 3500m in this area.
16
Raath, R. F., C. R. Penn-Clarke e A. F. M. Kisters. "Regional variance in alluvial sedimentation and revised stratigraphy of the Klipheuwel Group and Franschhoek Formation". South African Journal of Geology 127, n. 3 (1 settembre 2024): 641–64. http://dx.doi.org/10.25131/sajg.127.0033.
Testo completoAbstract (sommario):
Abstract The siliciclastic sediments of the Klipheuwel Group mark the transition from Pan-African tectonism and amalgamation of Southwest Gondwana to the shallow marine deposits of the Cape Supergroup in the Western Cape. The rocks are preserved in a number of seemingly isolated depositories and previous studies have mainly focused on selected occurrences. The lack of any integration of regional sedimentological or structural characteristics has, to date, resulted in only tentative stratigraphic correlations and subdivisions of the Klipheuwel Group. Lithological and structural data from the Klipheuwel Group indicate at least two separate depocentres that accommodated the post Pan-African peneplanation of the Saldania Belt and clastic detritus in distinctly different palaeoenvironments. A northern depocentre can be distinguished from a southern depocentre, each characterised by distinct architectural elements and facies associations that reflect topographic and structural controls. The northern depocentre, including Klipheuwel Group occurrences at Eendekuil, Redelinghuys and Elands Bay, show laterally persistent braided fluvial facies associations that developed multi-storey superimposed ‘braided sheet’ deposits. Here, the rocks show gentle dips and thicknesses range from 300 to 450 m. The southern depocentre, including the Klipheuwel and Klapmutskop localities, are characterised by much larger thicknesses (up to >2 000 m), steep dips of the rocks and laterally discontinuous braided fluvial facies associations that developed staggered channelised braided deposits. The lateral continuity of fluvial facies in the northern depocentre reflect sedimentation on a peneplained basement. The larger thickness, steep dips and strongly channelised deposits in the southern facies, in contrast, indicate deposition in actively subsiding half-graben structures that reactivated basement faults. The spatially closely associated Franschhoek Formation shares numerous characteristics with the Klipheuwel Group but preserves Pan-African strains similar to that of the underlying Malmesbury Group, that may indicate its formation as compressional piggyback basins with synorogenic sedimentation.
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Andrews-Speed, C. P. "The role of silica and iron oxide mobility in the formation of gold-bearing fluvial sediments in the Proterozoic Mporokoso Basin, northern Zambia". Geological Magazine 123, n. 2 (marzo 1986): 143–52. http://dx.doi.org/10.1017/s0016756800029794.
Testo completoAbstract (sommario):
AbstractGold-bearing sandstone and conglomerate near the base of the Proterozoic Mporokoso Group were deposited in a braided river system. The detrital sand grade material is mainly of quartz, sericite and haematite, and the pebbles are of vein-quartz, chert, silicic volcanics, quartzose metasediment and jaspilite. The basement rocks presently exposed in the basement are silicic igneous rocks and quartzose metasediments.The petrography of the fluvial sediments suggests that silica and, to a lesser extent, iron oxide were mobile both in the source-area and in the braided river system. Evidence for silica-mobility includes jaspilite pebbles with spherulites and glaebules of chalcedony, abundant vein-quartz pebbles, intra-basinal sandstone pebbles, and the silicification of volcanic pebbles. The detrital haematite in the fluvial sandstone forms pseudomorphs after magmatic magnetite. Authigenic iron oxide occurs in several forms which suggest that iron oxide was mobile in the source-area and in the fluvial sediments. Uranium is locally abundant in basement and sedimentary rocks, cassiterite is a common heavy mineral in the fluvial sediments, and fluorite has been found in the basement.These features may be explained by intense weathering which mobilized both silica and iron. The silica was concentrated near the surface to form silcretes in the basement and later in the overlying fluvial sediments. Hydrothermal convection cells driven by the granites may have carried silica, iron, tin, fluorine and uranium towards the surface before and during the erosion of the igneous basement.
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Fambrini, Gelson Luís, Diego da Cunha Silvestre, José Acioli Bezerra de Menezes-Filho, Ian Cavalcanti da Costa e Virgínio Henrique de Miranda Lopes Neumann. "Architectural and facies characterization of the Aptian fluvial Barbalha Formation, Araripe Basin, NE Brazil". Geological Society, London, Special Publications 488, n. 1 (2019): 119–50. http://dx.doi.org/10.1144/sp488-2017-275.
Testo completoAbstract (sommario):
AbstractThe Aptian Barbalha Formation records the beginning of the post-rift stage of the Araripe Basin. It consists predominantly of sandstones and mudstones interbedded with thin layers of bituminous black shales and conglomerates. The depositional and architectural features of the alluvial succession of the Barbalha Formation were characterized by detailed study and descriptions of the selected outcrops and analysis of well core data. In this study, two main depositional sequences were identified. The lower depositional sequence is more than 100 m thick and comprises a vertical facies succession composed of amalgamated, multistorey, braided fluvial channel sandstone bodies overlain by a widespread lacustrine black shale up to 10 m thick. The lacustrine black shales–carbonate mixed interval is known as the Batateira Beds and constitutes a regionally important stratigraphic correlation marker in the basin. This interval records the establishment of a large lake that experienced severe water-level fluctuations and anoxic events. The upper depositional sequence is 60–95 m thick, and mainly consists of thin, yellowish, medium- to fine-grained sandstones and variegated shales. The upper sequence rests unconformably on the lacustrine black shales of the Batateira Beds. Thin and discontinuous conglomerate beds at the base of the upper sequence laterally grade into coarse-grained sandstones. These coarse-grained sandstones are overlain by interbedded sandstones and mudstones organized in fluvial cycles. The upper and lower sequences of the Barbalha Formation are separated by an erosive unconformity, traceable throughout the study area, formed during a period of stratigraphic base-level lowering. This surface marks a change in the lower sequence from a dominantly fluvial depositional style, with amalgamated multistorey braided fluvial channel sand bodies, to a lacustrine system in the top to an eminently fluvial sedimentation, which in the basal section comprises amalgamated, multistorey, braided fluvial channel sand bodies, and in the superior section the amalgamated fluvial channels are overlain by floodplain and overbank sandstone bodies with fixed fluvial channel deposits, interpreted as a suspended-load-dominated fluvial system in the upper sequence. This change in the depositional style is accompanied by a reduction in grain size and a change in the fluvial regime, suggesting that the drainage system was restructured due to tectonic movements in the basin and climatic variations. In addition to the restructuring of the drainage basin, the characteristics of the discharge of the river system have changed, probably because of the more humid climatic conditions that dominated during the deposition of the upper sequence. The fluvial deposition in the lower sequence is associated with more ephemeral river systems, while the facies architecture of the upper sequence is associated with perennial systems and is suggestive of a suspended-load-dominated fluvial system. This fluvial system is capped by lacustrine deposits of the Crato Formation. The upper sequence grades upwards into the Crato Formation. The boundary between these two units is delineated by the presence of greenish calciferous shales that are covered by lacustrine laminated limestones and shales of Neoaptian age. Palaeocurrent readings from the fluvial deposits of both sequences display a consistent palaeoflow to the SE. Sedimentological and palaeontological evidence indicates a tectonic control on sedimentation and humid to subhumid climate conditions.
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García-Alix, Antonio, Raef Minwer-Barakat, Elvira Martín Suárez e Matthijs Freudenthal. "Small mammals from the early Pleistocene of the Granada Basin, southern Spain". Quaternary Research 72, n. 2 (settembre 2009): 265–74. http://dx.doi.org/10.1016/j.yqres.2009.06.004.
Testo completoAbstract (sommario):
AbstractThe Pliocene and Pleistocene continental sedimentary records of the western sector of the Granada Basin, southern Spain, consist of alternating fluvial and lacustrine/palustrine sediments. Two Quaternary sections from this sector have been sampled: Huétor Tájar and Tojaire. They have yielded remains of rodents, insectivores and lagomorphs. The presence in the Huétor Tájar and Tojaire sections of Mimomys, Apodemus atavus, Castillomys rivas and two different species of Allophaiomys, indicates an Early Pleistocene age. These deposits, which are related to a fluvio-lacustrine system, can be differentiated from an older (Pliocene) braided fluvial system. Their dating has important repercussions on the paleogeographic reconstruction of the basin. The conditions inferred from the ecological preferences of the small mammal associations are wet and cold. These associations suggest a predominance of open herbaceous habitats, followed by forested habitats; semiaquatic habitats are the least represented.
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Luo, Shun She, Fei Shang, Qi Qi Lv, Zhong Bao Liu e Ying Meng. "Influence of Hydrodynamics on Formation of Braided Fluvial Delta". Applied Mechanics and Materials 318 (maggio 2013): 453–59. http://dx.doi.org/10.4028/www.scientific.net/amm.318.453.
Testo completoAbstract (sommario):
The changes of hydrodynamics will influence the formation of braided river delta. Based on many previous studies, this article does some quantitative analysis of migration rate of channel, sedimentation position for sandbody and the shape of bar under the conditions of flood, common water and low water on the basis of sedimentary simulation techniques, and transportation model of sandbody is set up under the experimental condition. The results of flume experiment show that the difference exists in the position of the thickest sandbody under diffident hydrodynamic conditions. Migration rate of channel is the highest in common water period, followed by flood period and low water period. The ratio of sandbody width/height increases and the ratio of length/width decrease gradually from flood period to common water period to low water period.
21
Li, Shunli, Xinghe Yu, Bintao Chen e Shengli Li. "Quantitative Characterization of Architecture Elements and Their Response To Base-Level Change In A Sandy Braided Fluvial System At A Mountain Front". Journal of Sedimentary Research 85, n. 10 (1 ottobre 2015): 1258–74. http://dx.doi.org/10.2110/jsr.2015.82.
Testo completoAbstract (sommario):
Abstract: The Rockcave Member of the Yungang Formation (Middle Jurassic), in the Datong Basin, China, is a multistory sandstone that is interpreted as a sandy braided fluvial deposit based on grain size, lithofacies, and architectural elements. The depositional setting was the mountain front of the Datong Basin, which was tens of kilometers from the shoreline of a lacustrine basin during the Middle Jurassic. The concept of base level is used to analyze the architectural elements of the braided system obtained from photographic mosaics and high-resolution measurement of six outcrop sections from Yungang Rock Cave. Grain size, lithology, and bounding surfaces together with scale and dimension parameters of the sedimentary structures in various architectural elements were used to quantitatively characterize each group of architectural elements and stratigraphic units. Width/thickness values of trough crossbeds were found to be a fundamental component of the hydrodynamic regimes. During base-level rise the braided fluvial system developed large-scale channel units, bar units, and overbank fills. The relatively high proportion of bar units and overbank fills reflect processes operating during positive accommodation. However, during base-level fall there are a high proportion of small-scale channel units that reflect incision-dominated processes such as channels with low W/T values for trough crossbeds and less common overbank fines.
22
Xu, Qinghai, Wanzhong Shi, Xiangyang Xie, Changmin Zhang, Walter L. Manger, Jian Wang e Song Rao. "Multichannel systems in an ancient river-dominated delta: case study of the lower Yanchang Formation, southwest Ordos Basin, China". Canadian Journal of Earth Sciences 56, n. 10 (ottobre 2019): 1027–40. http://dx.doi.org/10.1139/cjes-2018-0277.
Testo completoAbstract (sommario):
Distributary channels in large deltas can form a channel pattern similar to braided fluvial system or anastomosed fluvial system that have multichannel systems. Although both systems are of generally comparable platforms, their geometry, sedimentology, and facies associations may exhibit unique characteristics. Many ancient multichannel systems have been interpreted as braided patterns, but some are certainly anastomosed patterns. A reevaluation of ancient multichannel architectures and sedimentology patterns is needed to improve discrimination of braided and anastomosed patterns of multichannel systems. This study examines the characteristics of two modern anastomosed pattern channel systems. Those modern systems are compared to ancient examples in the lower Yanchang Formation, southwest Ordos Basin. This comparison indicates that the multichannel systems of the delta, southwest Ordos Basin, exhibit greater similarity to modern anastomosed channel systems of shallow-water deltas. Systems of low-sinuosity distributary channels and interdistributary bays or swamp islands are developed mainly between the channels, and there are no mouth bar deposits. Both modern and ancient multichannel systems suggest that low gradient slope is a significant controlling factor in the formation of anastomosed pattern channels in river-dominated deltas. The identification of anastomosed patterns plays a significant role in reservoir characterization and hydrocarbon exploration and production in delta systems.
23
Malaza, Ntokozo, Kuiwu Liu e Baojin Zhao. "Facies Analysis and Depositional Environments of the Late Palaeozoic Coal-Bearing Madzaringwe Formation in the Tshipise-Pafuri Basin, South Africa". ISRN Geology 2013 (11 dicembre 2013): 1–11. http://dx.doi.org/10.1155/2013/120380.
Testo completoAbstract (sommario):
The late Palaeozoic coal-bearing Madzaringwe Formation of the Karoo Supergroup in the Tshipise-Pafuri Basin in the Limpopo Province, South Africa, records part of the infill of a passive continental margin terrain. Lithofacies analysis was performed with a view to deduce the nature of depositional environments of the Formation. Sedimentological and sequence stratigraphic evidence indicates that this unit represents a complex siliciclastic facies that reflects a fluvial paleodepositional environment. Eleven facies, which were grouped into five facies associations, were recognised. The base of the Madzaringwe Formation (Lower Member) represents a sequence deposited by braided channels. The coal deposits represent flood plain and swamp deposits, which is characterised by shale, thick coal seams, siltstone, and sandstone. The Middle Member is characterised by both clast and matrix supported conglomerates, major tubular and lenticular sandstones, and finely calcareous, micaceous siltstone. The deposition represents a sequence being formed from fluvial and particularly braided channels. The crudely stratified, coarse to pebbly sandstone indicates channel lag deposits within a heavy loaded fluvial system. The fine-grained sandstone represents deposition by shift channel and side bar deposits during lower flow conditions. The Upper Member is characterised by facies associations similar to the Lower Member, representing a new depositional cyclothem.
24
Preusser, Frank, Benjamin U. Müller e Christian Schlüchter. "Luminescence Dating of Sediments from the Luthern Valley, Central Switzerland, and Implications for the Chronology of the Last Glacial Cycle". Quaternary Research 55, n. 2 (marzo 2001): 215–22. http://dx.doi.org/10.1006/qres.2000.2208.
Testo completoAbstract (sommario):
AbstractThe advancing glaciers of the last glacial maximum either eroded or deeply buried older sediments in the Swiss Alpine Foreland. However, part of the Swiss Plateau was not covered by ice and is therefore an excellent area for investigating climate and environmental change during the Upper Pleistocene. Repeated fluvial sequences can be studied in several pits along the Luthern Valley. The chronological framework is based on lithostratigraphy, pollen analysis, U/Th dating, and recently, heavy mineral analysis and luminescence dating. The oldest unit, the Untere Zeller Schotter braided river deposit, represents cold climate conditions and presumably a glaciation prior to the Eemian Interglaciation. The last interglacial period and the very beginning of the last glacial cycle is represented by the Mittlere Zeller Schotter, sediments of a meandering fluvial system. Younger braided river sediments, the Obere Zeller Schotter, seem to correlate with the cold climate of oxygen isotope stage (OIS) 4. Weathering of the top of the Obere Zeller Schotter is likely to represent the OIS 3. The advancing Reuss glacier caused erosion of the recent Luthern Valley, cutting into older sediments, with local loess accumulation during the last glacial maximum as indicated by cover sediments on top of the fluvial sequence.
25
Daryono, Sapto Kis, Carolus Prasetyadi, Eko Teguh Paripurno, Sutanto Sutanto e Aditya Zaenalfi Faozi. "Facies and architectural analysis of Paleogen fluvial deposits of the measured section of Rambangnia and Air Napalan Rivers in Palembang Sub-basin". Journal of Earth and Marine Technology (JEMT) 3, n. 1 (12 ottobre 2022): 24–33. http://dx.doi.org/10.31284/j.jemt.2022.v3i1.3606.
Testo completoAbstract (sommario):
Paleogene fluvial deposits have an important problem as pre-rift deposits, which occur before or at the same time as the formation of the basin. The research results on facies analysis and interpretation of the depositional environment of Paleogene deposits located in the Garba Hills will later explain and describe the history of the formation and stratigraphic evolution of sedimentary rocks in the South Sumatra Basin, reflected in the lithological and facies characteristics. The facies analysis was carried out on a stratigraphic cross-section with a thickness of ± 107.37 meters and ± 11.06 meters on the measurement path of the Rambangnia River and Air Napalan River, which are located in the Ogan Komering Ulu area, South Sumatra. Seven lithofacies developed on two measured paths are matrix supported gradded gravel (Gmg), gravel matrix supported Massive (Gmm), through cross-bedded (St), massive sandstone (Sm), horizontally bedded sandstones (Sh), parallel laminated siltstone and claystone (F1), massive siltstones and mudstones (Fsm). Asosiasi fasies didapatkan berupa Sedimentary Gravity Flow (SG), Gravel Bars (GB), Sandy Bedforms (SB), channel (CH), Overbank fine (FF). The interpretation of the depositional environment shows a fluvial environment, the type of braided river with a gravel braided rivers model with sedimentary gravity flows.Paleogene fluvial deposits have an important problem as pre-rift deposits, which occur before or at the same time as the formation of the basin. The research results on facies analysis and interpretation of the depositional environment of Paleogene deposits located in the Garba Hills will later explain and describe the history of the formation and stratigraphic evolution of sedimentary rocks in the South Sumatra Basin, reflected in the lithological and facies characteristics. The facies analysis was carried out on a stratigraphic cross-section with a thickness of ± 107.37 meters and ± 11.06 meters on the measurement path of the Rambangnia River and Air Napalan River, which are located in the Ogan Komering Ulu area, South Sumatra. Seven lithofacies developed on two measured paths are matrix supported gradded gravel (Gmg), gravel matrix supported Massive (Gmm), through cross-bedded (St), massive sandstone (Sm), horizontally bedded sandstones (Sh), parallel laminated siltstone and claystone (F1), massive siltstones and mudstones (Fsm). Asosiasi fasies didapatkan berupa Sedimentary Gravity Flow (SG), Gravel Bars (GB), Sandy Bedforms (SB), channel (CH), Overbank fine (FF). The interpretation of the depositional environment shows a fluvial environment, the type of braided river with a gravel braided rivers model with sedimentary gravity flows.
26
Kasse, C., R. T. Van Balen, S. J. P. Bohncke, J. Wallinga e M. Vreugdenhil. "Climate and base-level controlled fluvial system change and incision during the last glacial–interglacial transition, Roer river, the Netherlands – western Germany". Netherlands Journal of Geosciences 96, n. 2 (19 dicembre 2016): 71–92. http://dx.doi.org/10.1017/njg.2016.50.
Testo completoAbstract (sommario):
AbstractThe fluvial development of the Roer river in the southeastern Netherlands and western Germany is presented for the Late Pleniglacial, Late-glacial and Early Holocene periods. Reconstruction of fluvial-style changes is based on geomorphological and sedimentological analysis. Time control comes from correlation to the pollen-based biochronostratigraphic framework of the Netherlands combined with independent optically stimulated luminescence (OSL) ages. At the Pleniglacial to Late-glacial transition a system and channel pattern change occurred from an aggrading braided to an incising meandering system. Rapid rates of meander migration, as established for the Late-glacial by optical dating, were likely related to the sandy nature of the substratum and the Late-glacial incision of the Meuse that resulted in a higher river gradient in the downstream part of the Roer. In the Roer valley the Younger Dryas cooling is not clearly reflected by a fluvial system response, but this may also be related to Holocene erosion of Younger Dryas fluvial forms. An important incision and terrace formation was established at the Younger Dryas to Early Holocene transition, probably related to forest recovery, reduced sediment supply and base-level lowering of the Meuse. The results of this study show a stepwise reduction in the number of channel courses from a multi-channel braided system in the Pleniglacial, to a double meander-belt system in the Late-glacial and a single-channel meandering system in the Early Holocene. The results show that the forcing factors of fluvial-system change in the Roer valley are climate change (precipitation, permafrost and vegetation) and downstream base-level control by the Meuse.
27
Moscariello, A. "The Schooner Field, Blocks 44/26a, 43/30a, UK North Sea". Geological Society, London, Memoirs 20, n. 1 (2003): 811–24. http://dx.doi.org/10.1144/gsl.mem.2003.020.01.68.
Testo completoAbstract (sommario):
AbstractThe Schooner Field is Shell U.K.'s first Carboniferous gas development in the North Sea. The field was discovered in 1987 by well 44/26-2 and gas production began in October 1996 from four wells. In contrast to the majority of the fields in the Southern North Sea producing from the aeolian Leman Sandstones Formation (Rotliegend), Schooner targets the low net-to-gross, fluvial Upper Carboniferous Barren Red Measures and Coal Measures formations. The reservoir consists of discrete, low sinuosity fluvio-deltaic channels draining a swampy coastal floodplain evolving upwards into a highly aggrading, low gradient, distal fluvial fan, dominated by braided and anastomosing channels. In Schooner, like other Carboniferous fields, reservoir connectivity is one of the key subsurface uncertainties due both to channel lateral discontinuity and fault compartmentalization. Production data and reservoir properties distribution, together with a new stratigraphical subdivision driven mostly by chemostratigraphic techniques, have been used to reassess the volume of gas-in-place which currently is estimated at 29.98 Gm3 (1059 BCF)
28
Ning, Zhao, Gao Xia, Chen Zhongmin, Huang Jiangqin e Zhang Guangya. "High Resolution Sequence Stratigraphy Correlation and Sedimentary Model of Braided Rivers: A Case on Paleogene Palogue Oilfield, South Sudan". E3S Web of Conferences 53 (2018): 03024. http://dx.doi.org/10.1051/e3sconf/20185303024.
Testo completoAbstract (sommario):
Complicated fluvial sands correlation and braided river models are still challenges for heterogeneous anisotropic reservoir evaluation for petroleum development in oilfields. Based on high-resolution sequence stratigraphy and sedimentology, core observation, and the analysis of logging and seismic data, high-resolution sequence stratigraphy framework of Paleogene Yabus formation of Palogue Oilfield, South Sudan is established, and sedimentary characteristics of braided rivers are analyzed, (1) In braided river deposits, channel bars are usually pro-gradating seawards and going thicker upwards. And braided channels are retro-gradating landwards and going thinner upwards. Both of them can be subdivided into channel (bar) trunks and channels (bar) flanks, showing vertical stacking and lateral migration; (3) As the A/S (Accommodation space/sediments supply) increasing upwards, braided river sands are shifting frequently as a reciprocating migration in Yabus V/VI, and they are more stable as the A/S decreasing upwards as a vertical aggradation in Yabus VII/VIII; (4) With 77 wells sedimentary microfacies identification, sand thickness and sand/bed ratio distribution, sedimentary facies distribution of all members and zones are analyzed. According to the A/S change, three braided river models are concluded, including isolated channel type (high A/S period), crossed channels type (medium A/S period), and superposed channels type (low A/S period).
29
Weckwerth, Piotr. "Palaeoslopes of Weichselian sand-bed braided rivers in the Toruń Basin (Poland): results of a palaeohydraulic analysis". Geologos 17, n. 4 (1 dicembre 2011): 227–38. http://dx.doi.org/10.2478/v10118-011-0013-6.
Testo completoAbstract (sommario):
Palaeoslopes of Weichselian sand-bed braided rivers in the Toruń Basin (Poland): results of a palaeohydraulic analysis Palaeoslopes of Weichselian sand-bed braided rivers have been reconstructed for two stages of fluvial development in the Toruń Basin. (1) The palaeoslope of the ‘fossil’ fluvial succession (buried under Weichselian tills) was calculated on the basis of the median grain size and the Shields parameter. The hydraulic gradient thus found is comparable with the hydraulic gradient of the present-day river. (2) The second developmental stage of the Toruń Basin (as a apart of the Noteć-Warta ice-marginal valley) took place after deglaciation. The slopes of river terraces are a few times lower than those calculated on the basis of the Shields parameter. The palaeoslope of the then river was estimated on the basis of a constant interdependency between the braidplain width, the channel geometry and the grain size. The river gradient that was thus calculated is similar to the measured terrace slope. Palaeoslope estimates in valleys similar to those in the Toruń Basin should consider the width of the braidplain.
30
Lin, Zhipeng, Le Chen, Jingfu Shan, Tan Zhang, Qianjun Sun e Yiwu Wang. "A New Sequence Stratigraphic Framework of Terrestrial Fluvial". Studies in Engineering and Technology 4, n. 1 (30 luglio 2017): 85. http://dx.doi.org/10.11114/set.v4i1.2521.
Testo completoAbstract (sommario):
Currently, the recognition and research on the classification of fluvial types mainly focus on the description and results of a series of indicators, such as the plane shape and sediment characteristics. However, there is limited literacy about how to demonstrate the fluvial types from the depositional process, especially less on sequence model of inland fluvial. Thus, this paper aims o propose a new kind of sequence stratigraphic framework, which is able to reflect the fluvial processes under the perspective of sequence stratigraphy. Accordingly, we use the principle of concrete analysis for concrete problems by comprehensively summing up the previous classification schemes of river types. With the research method of sedimentation process, new fluvial systems tracts for fluvial are presented here, including four parts: low fluvial system tract (LFST), advancing fluvial system tract (AFST), flooding fluvial system tract (FFST), receding fluvial system tract (RFST). Moreover, these could be applied to tackle the problem of the traditional division of fluvial. Various rivers have the different characteristics of systems tracts, then this may play a vital role in the discrimination of meandering river, braided river, anastomosing river and branched river. This study embodies the philosophical thought of Process Sedimentology and may contribute to revealing the deposition process of the fluvial system more profoundly from the aspect of genetic mechanism and evolution course. Most importantly, the fluvial classification system is definitely improved from the description stage to a complete rational stage.
31
Katona, Orsolya, György Sipos, Alexandru Onaca e Florina Ardelean. "Reconstruction of Palaeo-hydrology and fluvial architecture at the Orosháza palaeo-channel of River Maros, Hungary". Journal of Environmental Geography 5, n. 1-4 (2 gennaio 2012): 29–38. http://dx.doi.org/10.14232/jengeo-2012-43805.
Testo completoAbstract (sommario):
Several studies have addressed the impact of climate change and tectonic activity on fluvial systems. When investigating these systems palaeo-hydrological and geomorphological data on abandoned channels can yield valuable results. The main aim of our work was to reconstruct morphological conditions at the Orosháza palaeo-channel and to estimate the bankfull discharge which characterized the channel during its formation. There are several equations predicting bankfull discharge on the basis of planform parameters, but these only work for meandering rivers. In case of braided channels flow reconstruction can only be made by using cross-sectional parameters. The Orosháza palaeo-channel provided the means of a comparative analysis in this respect. By a sudden pattern change both meandering and braided reaches, supposedly having a very similar bankfull discharge, could be simultaneously studied. Planform parameters and present cross-sections were determined on the basis of a high resolution DEM, while original cross-section parameters were assessed using sedimentological and geophysical methods. Based on sedimentological data, channel pattern transition was mainly driven by intensive bedload accumulation at the edge of the Maros Alluvial Fan (MAF). Slope differences could not be evened out due to an avulsion close to the apex of the fan. Concerning discharge calculations a good agreement was found between a region-specific planform based equation and the cross-section based Grauckler-Manning equation. Values determined for the braided and meandering reach were also in a good correspondence. Consequently, the presented approach is suitable to determine the discharge of other braided palaeo-channels on the MAF and elsewhere.
32
Daryono, Sapto Kis, Afrilita Afrilita e Idarwati Idarwati. "Deposition Environment Interpretation of Lemat Formation in the West Tanjung Jabung, Jambi Province". Journal of Earth and Marine Technology (JEMT) 4, n. 2 (2 marzo 2024): 240–54. http://dx.doi.org/10.31284/j.jemt.2024.v4i2.5626.
Testo completoAbstract (sommario):
The study of facies analysis and interpretation of the depositional environment of the Lemat Formation located on Bukit Tigapuluh aimed to clarify the problems found in Paleogene sediments in the South Sumatra Basin. The results of research on facies analysis and interpretation of the depositional environment of the Lemat Formation will provide an explanation and description of the history of the formation and stratigraphic evolution of Paleogene-aged sedimentary rocks in the South Sumatra Basin as reflected in their lithological and facies characteristics. A detailed analysis of fluvial facies was carried out in the West Tanjung Jabung area, Jambi Province. A stratigraphic cross-section was prepared with an accumulated thickness of ± 25 m. The stratigraphic section included two rock deposits, namely sandstone-quartz deposits and conglomerate deposits. Analysis of lithofacies and architectural elements of the study area indicated a fluvial depositional environment. The resulting architectural elements consisted of six associations: channel (CH), scour hollows (HO), gravel bedform (GB), sediment gravity flows (SG), sandy bedform (SB), and floodplain fines (FF). The dominance of sedimentary material, which tends to be coarse, and the many facies associations GB, SG, and SB indicated many river bars and were characteristic of braided rivers. The obtained interpretation of the depositional environment was Conglomerate deposits in the Alluvial Fans System with Gravity Flow River environment or gravel bed braided river, and sandstone-gravel deposits in the shallow environment or gravel bed braided river.
33
Zhang, Zili, Xiaomin Zhu, Qi Li, Ruifeng Zhang, Jing Zhang e Yi Huang. "Depositional characteristics of fluvial facies in gentle slope zone of lacustrine rift basins: The third member of the Dongying Formation in the Wen’an Slope of Baxian Sag, Bohai Bay Basin, China". Interpretation 8, n. 2 (1 maggio 2020): SF37—SF55. http://dx.doi.org/10.1190/int-2019-0125.1.
Testo completoAbstract (sommario):
We have integrated core, well logs, and seismic data to analyze fluvial types and reconstruct sediment dispersal patterns of the Dongying Formation in the Wen’an Slope, Bohai Bay Basin (China). We analyzed four meandering-braided fluvial successions from the Dongying Formation in the Wen’an Slope. The results indicate that the fluvial systems are dominantly northeast–southwest and consist of channel, channel bar, and flood plain subfacies, which can be further subdivided into six microfacies including braided channel, meandering channel, sandy channel bar, muddy channel bar, crevasse fan, and floodplain. With a paleoflow direction, [Formula: see text] ranges from 40° to 65°, the river belt width [Formula: see text] is estimated to be 1.47–2.64 km, whereas the main channel width varies from 0.02 to 0.29 km and its thickness/bankfull depth [Formula: see text] ranges from 1.2 to 6.4 m. The differential subsidence of rift basin during fault-depression transition period is the main control on fluvial evolution and sand body distribution. The climatic effect causes changes in river flow. During the flood season, river flow and flow rate are large, and early sediments and sand bodies are reconstructed. Lateral erosion and undercutting are very strong in this period. In the dry season, the river is dominated by weak lateral erosion. Our study also suggests that the development of thick mudstone in the upslope may limit hydrocarbon charging and migration and thick channel and channel bar deposits in the middle and downslope cross cut by faults, which are conduits for migration are likely to be the most potential reservoirs in the Bohai Bay Basin.
34
Alege, T. S., J. I. Omada e K. Uchendu. "Field and Sedimentological Studies of Nataco-Banda Sediments of Lokoja Formation, Southern Bida Basin, Nigeria: Implication for Depositional Environment". Journal of Applied Sciences and Environmental Management 26, n. 11 (30 novembre 2022): 1835–42. http://dx.doi.org/10.4314/jasem.v26i11.15.
Testo completoAbstract (sommario):
The study area falls within the Lokoja Formation of the Southern Bida Basin. The objective of this study was to evaluate the field characteristics and sedimentological parameters of depositional environment of the Nataco-Banda Sediments of Lokoja Formation, Southern Bida Basin, Nigeria using appropriate techniques such as granulometric and pebble morphometric analysis. Field studies revealed a repeated alternating sequence of conglomeratic and pebbly to coarse-grained sandstone and overbank fine sediment that is indicative of a braided fluvial source while the presence of crossbedding is suggestive of tidal influence. The morphometric analysis shows a fluvial setting where pebbles plot in the river area than the beach area. Environmental discrimination formulae for Y1, Y2 and Y3 indicated the dominance of Beach and Shallow agitated marine in both Y1 and Y2, respectively, while the almost equal percentage values of Y3 in both fluvial and shallow marine settings are highly suggestive of a shallow marine environment that is largely influenced by fluvial deposition.
35
Hickin, Edward J. "Fluvial facies models: a review of Canadian research". Progress in Physical Geography: Earth and Environment 17, n. 2 (giugno 1993): 205–22. http://dx.doi.org/10.1177/030913339301700207.
Testo completoAbstract (sommario):
Canadian river scientists made significant contributions to the early development (1960-80) of fluvial facies models, particularly to those for braided rivers. More recent Canadian studies (1980-92) have centred on understanding the facies sedimentology of anastomosed and wandering gravel-bed rivers. River planform facies models are distinctly limited as indicators of fluvial style because of: (1) spurious environmental correlations; (2) the difficulty of river planform definition; (3) differential preservation potential of facies; (4) inadequate and unsystematic field sampling; (5) flawed statistical testing; and (6) the inappropriate space scale adopted for analysis. The scale problems of facies analysis may be overcome by employing architectural element analysis in conjunction with modem geophysical methods such as shallow reflection seismology and ground-penetrating radar. Future research should focus on devising specific tests of element-scale sedimentological relationships based on the contemporary fluvial enrivonment.
36
Slomka, J. M., e C. H. Eyles. "Characterizing heterogeneity in a glaciofluvial deposit using architectural elements, Limehouse, Ontario, Canada". Canadian Journal of Earth Sciences 50, n. 9 (settembre 2013): 911–29. http://dx.doi.org/10.1139/cjes-2013-0020.
Testo completoAbstract (sommario):
Major hydrocarbon and groundwater reservoirs are commonly hosted within coarse-grained alluvial deposits that contain a high degree of sedimentary heterogeneity. This paper presents a detailed characterization of the sedimentary heterogeneity of fluvial–deltaic deposits using architectural element analysis (AEA). Sedimentological data collected from outcrop faces exposing Late Quaternary glaciofluvial deposits in southern Ontario, Canada, is recorded in 31 sedimentary logs. These logs are used to identify nine different facies types, including gravel facies (Gm, Gp, Gt), sand facies (Sr, Sp, St, Ss), and fine-grained facies (Fl and Fd). Variations in facies associations and geometries are defined by five architectural elements (AEs): sand complex (SC), gravel sheet (GS), fine-grained sheet (FS), gravel foreset body (GFB), and concave fill (CF) elements. The spatial arrangement of bounding surfaces (first- to fifth-order) and AEs allows the classification of six EAs, which, in this study, are defined as the largest-scale architectural subunits that allow for architectural-based mapping over a large area. EAs delineated in this study are sandy braided-river (EA1), delta-front (EA2), gravelly braided-river to delta-top (EA3), delta-front to lacustrine (EA4), braided-river to deltaic (EA5), and sand-dominated fluvial (EA6). AEA is utilized here to capture three levels of heterogeneity, which allow detailed reservoir characterization based on geometric objects and can be readily used for computer-based modelling. Outcrop analogue studies such as this one provide insight to the geometries of more deeply buried coarse-grained deposits that form potential reservoirs and enhance paleoenvironmental reconstruction of subsurface alluvial deposits in Canada and elsewhere.
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Li, Jie, Junqiang Xia, Meirong Zhou, Shanshan Deng e Zenghui Wang. "Channel geometry adjustments in response to hyperconcentrated floods in a braided reach of the Lower Yellow River". Progress in Physical Geography: Earth and Environment 42, n. 3 (giugno 2018): 352–68. http://dx.doi.org/10.1177/0309133318776492.
Testo completoAbstract (sommario):
Hyperconcentrated floods with more than 200–300 kg/m3 sediment concentrations often occur in the Lower Yellow River (LYR) during flood seasons, which leads to unique fluvial processes in the braided reach of the LYR. The investigation of channel geometry adjustments in response to hyperconcentrated floods can not only help to gain a better understanding of associated fluvial processes, but also is significant for making flood control strategies in the braided reach. In this study, pre- and post-flood bankfull channel dimensions in the braided reach were calculated based on the observed cross-sectional profiles in 15 years with the occurrence of hyperconcentrated flood events. Adjustments in channel geometry at section- and reach-scales were investigated, with several factors influencing adjustments in reach-scale channel geometry being analyzed. It indicates that the mean sediment transport rate was a key factor influencing the adjustment index, although pre-flood channel geometry and sediment deposition can also affect the index to some extent. An empirical relationship was developed between the characteristic parameter representing the pre- and post-flood channel geometries and mean sediment transport rate in hyperconcentrated floods. Eleven datasets were used to calibrate the parameters in the empirical relation, with the datasets in 1973, 1988, 1995, and 2002 verifying the relation. The calculated post-flood characteristic parameter of channel geometry using the empirical relation agreed well with observed data, and the proposed method can be used to predict the reach-scale adjustment of channel geometry during hyperconcentrated floods in alluvial rivers.
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VALENCIA, GUSTAVO L., LUIS A. BUATOIS, M. GABRIELA MÁNGANO, MARTIN E. FARINA e VERÓNICA KRAPOVICKAS. "EVALUATING TRACE FOSSILS, FLUVIAL ARCHITECTURE, AND COLONIZATION PATTERNS IN CHANNEL AND OVERBANK DEPOSITS FROM THE MIOCENE VINCHINA FORMATION, WESTERN ARGENTINA". Palaios 39, n. 10 (24 ottobre 2024): 363–83. http://dx.doi.org/10.2110/palo.2023-038.
Testo completoAbstract (sommario):
Abstract Trace-fossil distribution within the framework of three-dimensional fluvial architecture has been commonly overlooked. The Miocene Vinchina Formation in western Argentina preserves extensive outcrops of fluvial deposits, including architectural elements of both anastomosing and braided systems identified along the Quebrada de La Troya. Multistorey sandy channels, amalgamated sandy channels, heterolithic multistorey channels, channels with gravel bars, abandoned channels, muddy floodplains, crevasse splays, and crevasse channels have been identified. Of these, only the deposits of three elements were bioturbated, namely crevasse splays, anastomosing abandoned channels, and braided abandoned channels. Vertical simple burrows (Skolithos isp.), large-sized J burrows (Capayanichnus vinchinensis), and simple horizontal burrows (Palaeophycus tubularis) are the most common trace fossils in the Vinchina Formation. Other elements include the horizontal meniscate trace Taenidium barretti and the vertebrate footprints Tacheria troyana, Macrauchenichnus troyana, and Ardeipeda isp. The trace-fossil assemblages identified in the Vinchina Formation collectively illustrate the Scoyenia Ichnofacies. In addition, five ichnofabrics are characterized. The position of the water table, substrate consistency, flow energy, and time between depositional events under arid to semi-arid climate conditions were the main parameters controlling bioturbation. Based on detailed observation of the cross-cutting relationship among ichnotaxa, the ichnofabric distribution and the preservation features of the trace fossils studied, a colonization sequence for each of the subenvironments of the Vinchina Formation is proposed in this study. In addition to integration with conventional facies analysis, articulating ichnologic data and fluvial architecture provides further insights into the application of trace fossils to unravel the sedimentary dynamics of alluvial systems.
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Martin, John H. "A review of braided fluvial hydrocarbon reservoirs: the petroleum engineer’s perspective". Geological Society, London, Special Publications 75, n. 1 (1993): 333–67. http://dx.doi.org/10.1144/gsl.sp.1993.075.01.20.
Testo completo
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Wang, Xixin, Fan Zhang, Shaohua Li, Luxing Dou, Yuming Liu, Xiaoxu Ren, Depo Chen e Wen Zhao. "The Architectural Surfaces Characteristics of Sandy Braided River Reservoirs, Case Study in Gudong Oil Field, China". Geofluids 2021 (29 aprile 2021): 1–12. http://dx.doi.org/10.1155/2021/8821711.
Testo completoAbstract (sommario):
The architecture analysis of the different orders sedimentary bodies is of great significance to the efficient development of oil and gas fields. In order to investigate the effects of the architectural interfaces on reservoir quality and heterogeneity, this study takes the Gudong oil field as a case to investigate the architectural characteristics of hierarchical bounding surfaces using detailed descriptions of core and wireline logs. Architectural models from the 7th-order to the 3rd-order are analyzed, and the developmental characteristics of the 5th-order braided river, 4th-order single sandstone, and 3rd-order accretion are summarized. The interlayer between two braided rivers is floodplain mud deposition, with poor physical properties, stable thickness, and strong blocking capacity. Two models of interlayers are found in the 4th-order deposition. The first interlayer is between the braided filling channel and midchannel bar, which is composed of generally fine-grained sediments with calcium cementation and poor physical properties. The second interlayer is a transformation belt between two midchannel bars and is generally composed of gravel-scoured deposition with penetration capability. The 3rd-order surfaces are defined as the surfaces of accretions within midchannel bars. Two models of interlayers are also found in the 3rd-order surfaces of accretions. The paleocurrent of the sandy braided river is reconstructed by synthesizing the core data, well logging data, and production performance data. A total of 1 fluvial system (7th-order), 2 compound braided rivers (6th-order), 11 braided rivers (5th-order), 41 midchannel bars (4th-order), and 96 accretions (3rd-order) are developed in the study area.
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Schwartz, Theresa M., Marieke Dechesne e Kristine L. Zellman. "Evidence for variable precipitation and discharge from Upper Cretaceous–Paleogene fluvial deposits of the Raton Basin, Colorado–New Mexico, U.S.A." Journal of Sedimentary Research 91, n. 6 (10 giugno 2021): 571–94. http://dx.doi.org/10.2110/jsr.2020.081.
Testo completoAbstract (sommario):
ABSTRACT The Raton Basin of Colorado–New Mexico, USA, is the southeasternmost basin of the Laramide intraforeland province of North America. It hosts a thick succession (4.5 km or 15,000 ft) of Upper Cretaceous to Paleogene marine and continental strata that were deposited in response to the final regression of the Western Interior Seaway and the onset of Laramide intraforeland deformation. The Upper Cretaceous–Paleogene Raton and Poison Canyon formations were previously described as meandering river and braided river deposits that represented distal and proximal members of rivers that drained the basin-bounding Sangre de Cristo–Culebra uplift. We present new observations of fluvial-channel architecture that show that both formations contain the deposits of sinuous fluvial channels. However, fluvial channels of the Raton Formation formed in ever-wet environments and were affected by steady discharge, whereas channels of the overlying Poison Canyon Formation formed in drier environments and were affected by variable discharge. The apparent transition in fluvial discharge characteristics was coeval with the progradation of fluvial fans across the Raton Basin during the Paleocene, emanating from the ancestral Sangre de Cristo–Culebra uplift. The construction of fluvial fans, coupled with the sedimentary features observed within, highlights the dual control of Laramide deformation and early Cenozoic climatic patterns on the sedimentary evolution of the Raton Basin.
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Waksmundzka, Maria I. "Braided-river and hyperconcentrated-flow deposits from the Carboniferous of the Lublin Basin (SE Poland) – a sedimentological study of core data". Geologos 18, n. 3 (1 novembre 2012): 135–61. http://dx.doi.org/10.2478/v10118-012-0008-y.
Testo completoAbstract (sommario):
Abstract Fining-upwards cyclothems found in five boreholes in the Carboniferous (Lower Bashkirian) of the Lublin Basin were analysed sedimentologically. It was established that the cyclothems represent fluvial deposits, and the lithofacies were grouped into lithofacies associations. Most lithofacies associations represent three types of sand-bed braided rivers: (1) high-energy, (2) deep and (3) distal sheetflood-affected. Other associations represent hyperconcentrated flows. Both coarse-grained (type I) and fine-grained (types IIa and IIb) occur among the fining-upward cyclothems. The formation of most thick cyclothems was related mainly to allocyclic factors, i.e. a decrease in the river’s gradient. The thickest fining-upward cyclothems are characteristic of hyperconcentrated flows and braided-river channels. The aggradation ratios were commonly high. During the early Namurian C and early Westphalian A (Early Bashkirian), the eastern part of the Lublin Basin was located close to the source area. The sedimentary succession developed due to a transition from high-energy braidedrivers and hyperconcentrated flows to lower-energy braided rivers, controlled by a rise of the regional base level.
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Marghani, Mouna M. A., e Abdulhadi Elsounousi Khalifa. "Formation Evaluation of the Lower Cretaceous Nubian Formation, East Sirt Basin, Libya". International Science and Technology Journal 35, n. 1 (1 ottobre 2024): 1–38. http://dx.doi.org/10.62341/mafe3510.
Testo completoAbstract (sommario):
It is crucial to gain a deeper comprehension of the factors that influence reservoir quality in low-porous heterogeneous reservoirs for the purpose of petroleum exploration and production. This research examines the depositional and post-depositional influences on the sandstone reservoir quality of the Upper Nubian Member in the North Gialo Field, East Sirt Basin, Libya. To explore the connection between facies and petrophysical parameters and to determine the impact of fractures on enhancing the pore system in low-porous reservoirs, core analysis, petrography analysis, and petrophysical measurements are integrated. The study revealed that the Upper Nubian Member is a very heterogeneous reservoir with major lateral and vertical quality variations, and has low porosity and fair permeability. The reservoir can be subdivided into seven lithofacies and grouped into four dominant facies associations (FAs) (i.e., flood plain, crevasse splay, meandering channel, and braided channel) based on sedimentological analysis. Analysis of various lithofacies associations within the fluvial environment indicates that the fluvial meandering and braided channel sandstones exhibit superior reservoir quality. In contrast, the crevasse splay lithofacies associations demonstrate moderate reservoir quality, whereas the flood plain lithofacies association, as anticipated, showcases the poorest reservoir quality owing to its high detrital clay content. The examination of facies, petrography, and routine core analysis (RCAL) data indicated that mechanical compaction, quartz overgrowth, and clay cement precipitation are the primary factors influencing the deterioration of reservoir quality, whereas feldspar and anhydrite dissolution, along with fractures, contributed to the improvement of reservoir quality. The analysis of fracture characteristics and image logs demonstrated the substantial impact of fractures on the permeability of low-porosity fluvial sediments, with five predominant fracture types shaping the fracture network within the reservoir under investigation. The study delineates the source of fractures and their impact on fluid migration, fluid flow, and the improvement of reservoir quality. It also illustrates the function of fractures as pathways through the less porous sand units. Additionally, it offers guidance and insight for reservoir development in the quest for high-quality sweet spots in low-porosity fluvial reservoirs. Keywords: Fluvial sandstone; Facies analysi; Nubian Formation; Sirt Basin; Libya.
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Weckwerth, Piotr, Krzysztof Przegiętka, Alicja Chruścińska, Barbara Woronko e Hubert Oczkowski. "Age and sedimentological features of fluvial series in the Toruń Basin and the Drwęca Valley (Poland)". Geochronometria 38, n. 4 (1 dicembre 2011): 397–412. http://dx.doi.org/10.2478/s13386-011-0038-1.
Testo completoAbstract (sommario):
Abstract The deposits of the Toruń Basin are dominated by a few-metre thick sand series which fill up buried valley-like depressions. In many cases they underlie the Weichselian till which builds up the ice marginal streamway (pradolina) terraces or they are exposed at the basin slopes. As the results of the geological and sedimentological studies, as well as of the dating of the deposits at the sites in the Toruń Basin indicate, the deposits include two fluvial series accumulated before the advancement of the Leszno Phase ice sheet, i.e. in Middle Weichselian and at the beginning of Late Weichselian. The oldest fluvial series connected with the Saalian Glaciation was found at the mouth section of the Drwęca Valley. The fluvial system of the Toruń Basin during Middle Weichselian and at the beginning of Late Weichselian developed in two phases of the sand-bed braided river. During the first one the river channel were dominated by large mid-riverbed sandbars, while during the second phase the water flow was smaller and, as a result, low transverse sandbars and two-dimensional dunes developed. Other active river channel also showed low-energy flows, more intensive meandering than in the case of the braided rivers, as well as sandy side-bars. Analysis of the rounding and frosting of the quartz grains indicate that the studied series of the Weichselian sandy deposits represent alluvia of a river which were fed from two diverse sources. The first one might have represented the alluvia of a warm river which transformed its load, while the other one might have mainly carried the underlying Quaternary deposits.
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Bukar, Shettima, Mohammed Bukar, Asabe Kuku, Bintu Shettima e Ishaku H. Kamale. "Incised Valley Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-basin Northern Benue Trough N.E. Nigeria". European Journal of Engineering Research and Science 5, n. 8 (19 agosto 2020): 870–76. http://dx.doi.org/10.24018/ejers.2020.5.8.1999.
Testo completoAbstract (sommario):
This research was carried out in the Gongola Sub-basin of the Northern Benue Trough aimed at deciphering of the paleo-depositional environment of the Yolde Formation based on facies on facies analysis. Six lithofacies were identified to include trough crossbedded sandstone facies (St), massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel sandstone facies (Sl) and mudstone facies (Fm). These build into two facies association of fluvial channel and tidally influenced fluvial channel facies associations. The fluvial successions typical characterizes the lower stratigraphic horizons and their contained dominances of trough crossbedded sandstone facies with high channel to overbank facies and contained mud-clast reflecting deep, high energy braided river system. The submergences of these channels by surging sea level rise generated the tidally influenced fluvial facies association and this package characteristically defines the upper interval stratigraphic architecture of this formation, displaying occasional bi-directional current system and abundant marine ichnogenera. This architectural symmetry is reflective of an incised valley fills, developing as a consequence of Cenomanian transgressive phase induced by the mid-Cretaceous global marine transgression.
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Bukar, Shettima, Mohammed Bukar, Asabe Kuku, Bintu Shettima e Ishaku H. Kamale. "Incised Valley Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-basin Northern Benue Trough N.E. Nigeria". European Journal of Engineering and Technology Research 5, n. 8 (19 agosto 2020): 870–76. http://dx.doi.org/10.24018/ejeng.2020.5.8.1999.
Testo completoAbstract (sommario):
This research was carried out in the Gongola Sub-basin of the Northern Benue Trough aimed at deciphering of the paleo-depositional environment of the Yolde Formation based on facies on facies analysis. Six lithofacies were identified to include trough crossbedded sandstone facies (St), massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel sandstone facies (Sl) and mudstone facies (Fm). These build into two facies association of fluvial channel and tidally influenced fluvial channel facies associations. The fluvial successions typical characterizes the lower stratigraphic horizons and their contained dominances of trough crossbedded sandstone facies with high channel to overbank facies and contained mud-clast reflecting deep, high energy braided river system. The submergences of these channels by surging sea level rise generated the tidally influenced fluvial facies association and this package characteristically defines the upper interval stratigraphic architecture of this formation, displaying occasional bi-directional current system and abundant marine ichnogenera. This architectural symmetry is reflective of an incised valley fills, developing as a consequence of Cenomanian transgressive phase induced by the mid-Cretaceous global marine transgression.
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Gao, Peng, Barbara Belletti, Hervé Piégay, Yuchi You e Zhiwei Li. "Can Water-Detection Indices Be Reliable Proxies for Water Discharges in Mid-Sized Braided Rivers Using Coarse-Resolution Landsat Archives?" Remote Sensing 16, n. 1 (28 dicembre 2023): 137. http://dx.doi.org/10.3390/rs16010137.
Testo completoAbstract (sommario):
The use of water detection (WD) indices to infer daily discharge (Qd) has a great potential to enrich needed hydrological data for understanding fluvial processes driving the morphological changes of braided rivers. However, no consensus has been reached on which one stands out for use in mid-sized braided rivers. In this study, we compared the physical characteristics of three most commonly used WD indices, the Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (MNDWI), and Normalized Difference Moisture Index (NDMI), for two mid-sized braided reach segments in the Qinghai-Tibet Plateau, China, that have different morphological structures. Relying on the Google Earth Engine web interface, we calculated the total mean water width (WWt) based on the detected surface-water areas (As) and braiding index (BI), as well as the mean values (m) of these indices over about four decades at the braided corridor scale (cs) (mNDWIcs, mMNDWIcs, and mNDMIcs). We then examined different responses of these indices to water and non-water features and their best threshold values for characterizing channel structures. Our analyses demonstrated that (1) NDWI and MNDWI perform well for detecting braided channel structures with the threshold of zero; (2) WWt is generally better correlated to Qd in a linear style than WD indices do, particularly when calculated from MNDWI; and (3) among WD indices calculated at the braided corridor scale, mMNDWIcs shows a better relationship with Qd than mNDMIcs does. Finally, we provided mechanisms that may explain these differences in terms of photometric discrepancies in calculating WWt and WD indices and the impact of image resolution on their calculations.
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Lakshminarayana, G. "Gondwana Sedimentation in the Chintaiapudi Sub-basin Godavari Valley, Andhra Pradesh". Journal Geological Society of India 46, n. 4 (1 ottobre 1995): 375–83. http://dx.doi.org/10.17491/jgsi/1995/460408.
Testo completoAbstract (sommario):
Abstract A 3000 m thick Gondwana lithic fill consisting of multifacies associations were preserved in a NW-SE oriented intracratonic Chintalapudi sub-basin set across the Eastern Ghat Complex (EGC). Sedimentation commenced with the deposition of diamictite-rhythmite sequence of the Talchir Formation in glacio-lacustrine environment. The succeeding sandstone-coal cyclothems of the Barakar Formation were formed in fluvial-coal swamp complex. The fluvial streams flowed across the EGC, originating somewhere in the southeast beyond the East Coast of India. Phase-wise upliftment of the EGC during Mesozoic imparted changes to the Permian intercontinental drainage system which started supplying increased aJll'lOunt of detritus to the basin. Basin marginal faults were first formed at the beginning of Triassic. Alluvial fans originated in the east and southeast and northwesterly flowing braided streams deposited the conglomerate-sandstone sequence of the Kamthi Formation. The Early Jurassic uplift of the Mailaram high in the north imparted westerly shift to the braided rivers during the Kola sedimentation . Due to prominence of Kamavarapukota ridge in the south by Early Cretaceous, the drainage pattern became centripetal and short-lived high sinuous rivers debouched into the basin. The silting up of the Chintalapudi sub-basin with tbe sandstoneclaystone sequence of the Gangapur Formation marks the culmination of the Gondwana sedimentation, perhaps, coinciding with the breakup of India from the Gondwanaland.
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Noll, C. A., e M. Hall. "FLUVIAL ARCHITECTURE AND THE TECTONIC CONTROL ON DEPOSITION OF ONSHORE EUMERALLA FORMATION, OTWAY RANGES, VICTORIA: IMPLICATIONS FOR EXPLORATION IN THE EARLY CRETACEOUS OTWAY BASIN". APPEA Journal 43, n. 1 (2003): 99. http://dx.doi.org/10.1071/aj02005.
Testo completoAbstract (sommario):
Spectacular outcrops of the terrestrial Aptian-Albian Eumeralla Formation are exposed in the Skenes Creek– Wongarra region, located on the eastern margin of the Otway Ranges, Victoria. The succession comprises mudstone-dominated floodplain and lacustrine successions and fluvially-derived sandstones. Lithofacies observed in the study area comprise intraformational and exotically derived conglomerate, massive and planar laminated sandstone, trough and tabular cross-bedded sandstone, ripple laminated sandstone, interbedded sandstone and mudstone, massive to laminated mudstone and thin coal seams. Architectural analysis of the fluvial system reveals these lithofacies are arranged into architectural elements that include channel elements, sandy bedforms, downstream and lateral accretion elements, laminated sand sheets and overbank fines elements.The fluvial system is characterised by low-sinuousity, braided river channels with high width to depth ratios. Palaeocurrent data indicates that the generally westward palaeoflow is interpreted to have been diverted into local axial-through drainage patterns by active northeast trending normal faults. One of these, the Skenes Creek Fault, is also likely to have structurally isolated floodplain and lacustrine successions from the main channel belt, leading to the deposition of an anomalously thick coal measure sequence in the hanging wall of the fault. The local study therefore provides insight into regional lithofacies and potential source rock distributions, and the associated tectonostratigraphic evolution of the Eumeralla Formation in the eastern Otway Basin. While the nature of the Eumeralla Formation sandstone does not lend itself to good reservoir properties, the geometry and internal structure of the sands provide an excellent model for other fluvial sandstone reservoir reconstructions.
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Oyanyan, Raphael Oaikhena, Modestus Chijioke Ohaegbulem, Christian Chukwudi Agbo e Nonyelum Stella Iloanya. "SEDIMENTARY ARCHITECTURAL ELEMENTS AND SANDY BRAIDED FLUVIAL SUCCESSIONS IN AJALI SANDSTONE RIDGES, WESTERN AFIKPO BASIN, UTURU, NIGERIA". Earth Science Malaysia 5, n. 1 (29 dicembre 2020): 49–57. http://dx.doi.org/10.26480/esmy.01.2021.49.57.
Testo completoAbstract (sommario):
Lithofacies, bounding surfaces and sedimentary architectural elements exposed in two ridges at Uturu being quarried for construction sands were analysed to determine the paleoenvironment of deposition and the factors that control the deposition of sand units. Mainly outcropped is Ajali Formation overlying locally exposed Mamu Formation in Western Afikpo basin. Lithofacies identified include: Trough cross bedded medium- to coarse-grained (St), Planar cross bedded fine- to coarse-grained sandstone (Sp), Small scale planar cross bedded sandstone (SSp), Lenticular mudstone (Fm), Heterolithic sandstone/mudstone (Fsm), Horizontal stratified sandstone (Sh), Cross ripple laminated sandstone (Sr), Reddish muddy sand (Fl), Siltstone (SSm) and Shale (Fsh). The associations of lithofacies and bounding surfaces gave four fluvial and one marine architectural element. The fluvial elements which mainly characterized the Ajali Formation include: Channel-fill (CH), Macroforms Accretion (MA). Flood-Plain Fines (FF) and Channel Abandonment Fines (CAF). Offshore-shoreface fines (OSF) element defined marine Mamu Formation. The profiles of the ridges show dominance of MA followed by CH while FF is limited in occurrence and in some zones pinch-out to lenticular inter-bar mudstone. The MA is characterized by planar cross beddings, reactivation surfaces, internal grading, steep dipping ferruginized accretion surfaces and abrupt flat top which indicate mid-channel bars deposition in typical sandy braided fluvial depositional system. Generally, there is vertical aggradation/ amalgamation of channel deposits and dominance of sheet alluvial architecture. Low rate of channel avulsion, moderate rate of lateral migration and aggradation, variable discharge rate and high rate of sediment supply and subsidence were considered as factors that controlled the deposition and preservations of sand units. This study provided an understanding of mesoscopic heterogeneities and compartmentalization style inherent in hydrocarbon bearing sandy braided reservoirs which can be used as analog model for its development.