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D W Lewis - One of the best experts on this subject based on the ideXlab platform.
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trace fossils and paleoenvironmental control of ichnofacies in a late quaternary gravel and loess Fan Delta complex new zealand
Palaeogeography Palaeoclimatology Palaeoecology, 1991Co-Authors: A A Ekdale, D W LewisAbstract:Abstract Remarkably well-preserved trace fossil assemblages of a small, Late Quaternary (> 3000 yr B.P.) Fan Delta complex are exposed in sea cliffs south of Conway Flat, North Canterbury, New Zealand. Marine trace fossils are common and well-preserved in the bar, embayment and proDelta facies, but Deltaic distributary facies contain no trace fossils at all. The preceding paper in this journal ( Lewis and Ekdale, 1991 ) describes the lithofacies and their paleoenvironmental setting in this Fan Delta complex. Common trace fossils include the ichnogenera Anconichnus, Arenicolites, Asterosoma, Cylindrichnus, Diplocraterion, Gordia, Helminthoida, Ophiomorpha, Piscichnus, Planolites and Skolithos . One new ichnogenus ( Arborichnus ), two new ichnospecies ( Arborichnus sparsus and Diplocraterion asymmetrium ), and three informal varieties of Diplocraterion parallelum (var. lingum, arcum and quadrum ) are introduced. Local ichnofacies include (a) low-divsity Anconichnus horizontalis Ichnofacies of densely packed burrows of deposit-feeding animals in shallow-marine, fine-grained sediment of bar and distal embayment facies, (b) high-diversity Diplocraterion parallelum var. lingum Ichnofacies of burrows of suspension-feeding animals in interbedded mud, clean sand and gravelly sand of the bar facies, (c) moderate-diversity Diplocraterion parallelum var. quadrum Ichnofacies in interbedded mud and sand of distal embayment facies, and (d) low-diversity Planolites montanus Ichnofacies of deformed burrows in bioturbated mud of the proDelta facies. In addition, sparse animal escape structures (fugichnia) occur locally in interbedded sand and gravel of the bar facies. The trace fossil associations of the Conway Flat Fan Delta complex are unusual in their excellent state of preservation, and many trace fossils are exposed in full-three-dimensional relief. Because of their very young age, they must reflect similar associations of biogenic sedimentary structures in modern Deltaic settings that are as yet undescribed. This report appears to be the first documentation of a fully marine trace fossil assemblage in loessial sediments.
S. K. Chough - One of the best experts on this subject based on the ideXlab platform.
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The Maesan Fan Delta, Miocene Pohang Basin, SE Korea: architecture and depositional processes of a high‐gradient Fan‐Delta‐fed slope system
Sedimentology, 2000Co-Authors: I. G. Hwang, S. K. ChoughAbstract:The Maesan Fan-Delta-fed slope system in the Miocene Pohang Basin occurs between two Gilbert-type Fan Deltas. Detailed analysis of sedimentary facies and bed geometry reveals that the sequence is represented by 13 sedimentary facies. These facies can be organized into three facies associations, representing distinct depositional environments: alluvial Fan (facies association I), steep-faced slope (facies association II), and basin plain (facies association III). Subaerial debris flows and dense, inertia-dominated currents were transformed into subaqueous sediment gravity flows in steep-faced slope environments. Further downslope, these flows were channelized and formed lobate conglomerate and sandstone bodies at the terminal edge of the channels (or chutes). Interchannel and interlobe areas were dominated by homogeneous mudstone and muddy sandstone, deposited by suspension settling of fine-grained materials. Part of the steep-faced slope deposits experienced large-scale slides and slumps. The chutes/channels, lobes and splays on the steep-faced slope of the Maesan system are similar to those in modern subaqueous coarse-grained Fan-Delta systems.
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the maesan Fan Delta miocene pohang basin se korea architecture and depositional processes of a high gradient Fan Delta fed slope system
Sedimentology, 2000Co-Authors: I. G. Hwang, S. K. ChoughAbstract:The Maesan Fan-Delta-fed slope system in the Miocene Pohang Basin occurs between two Gilbert-type Fan Deltas. Detailed analysis of sedimentary facies and bed geometry reveals that the sequence is represented by 13 sedimentary facies. These facies can be organized into three facies associations, representing distinct depositional environments: alluvial Fan (facies association I), steep-faced slope (facies association II), and basin plain (facies association III). Subaerial debris flows and dense, inertia-dominated currents were transformed into subaqueous sediment gravity flows in steep-faced slope environments. Further downslope, these flows were channelized and formed lobate conglomerate and sandstone bodies at the terminal edge of the channels (or chutes). Interchannel and interlobe areas were dominated by homogeneous mudstone and muddy sandstone, deposited by suspension settling of fine-grained materials. Part of the steep-faced slope deposits experienced large-scale slides and slumps. The chutes/channels, lobes and splays on the steep-faced slope of the Maesan system are similar to those in modern subaqueous coarse-grained Fan-Delta systems.
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a gravel lobe deposit in the proDelta of the doumsan Fan Delta miocene se korea
Sedimentary Geology, 2000Co-Authors: J W Kim, S. K. ChoughAbstract:Abstract The Doumsan Fan-Delta system in the Pohang Basin (Miocene), SE Korea comprises tripartite components of Gilbert-type topset, foreset, and bottomset environments with an extended proDelta in the deeper part (a few hundred metres deep). The present study documents sedimentologic features and origin of a gravel body (here interpreted as a gravel lobe) formed in the proDelta region of the Doumsan Fan Delta. The gravel lobe lies on sandy mud deposits and is capped by a thick massive sand bed. It extends for more than 1.5 km with a height of up to 30 m and shows a narrow tongue-like geometry. Eight sedimentary facies have been distinguished to describe characteristic features of the gravel lobe and the associated deposits. Of these, three types of gravelly sedimentary facies are important with regard to volumetric contribution and depositional processes: (1) crudely stratified pebble-grade conglomerate; (2) disorganized, clast-rich pebble(-to-cobble)-grade conglomerate; and (3) matrix-rich, bimodal cobble-grade conglomerate. The former two types dominate the central part of the lobe where they are not accompanied by sand beds, whereas the latter, as subordinate units, is prevalent in the fringe which otherwise is dominated by thick sandy mud deposits. The stacked successions of crudely stratified pebble-grade conglomerate are representative of the active aggradational phases of the gravel lobe, whereas the occurrence of channels within the lobe reflects that the gravel lobe prograded under the influence of subaqueous channel systems. The gravel lobe resulted from catastrophic disturbance (slumping) on the foreset region that further caused the development of channel systems, promoting efficient transport of gravelly sediments. This type of deposit may represent an important additional category of low-efficiency subaqueous Fans.
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provenance of coarse grained detritus in Fan Delta systems miocene pohang basin se korea implications for boundary fault movements
Geosciences Journal, 1998Co-Authors: S W Hong, S. K. Chough, I. G. HwangAbstract:In Fan-Delta systems, contemporary activities of boundary faults can be effectively constrained by tracing coarse-grained detritus. In order to reveal provenance and tectonic activities in the western margin of the Pohang Basin (Miocene), a total of 6000 clasts were examined in four FanDelta systems for composition and compared with probable source rocks in the drainage area. Clasts in the Doumsan, Maesan, and Duksung Fan-Delta systems are dominated by granite, granodiorite, gray mudstone, and sandstone with subordinate amounts of rhyolite, dacite, and tuff. The Malgol FanDelta system comprises silicic volcanics (mainly dacite), red or light gray sandstone, and mudstone. These clasts are similar in composition to the rocks exposed in the drainage area (Cretaceous Banyawol and Kisadong formations and Eocene granite and dacite bodies). The results indicate that strike-slip movements along the basin margin were inactive during the deposition of these Fan Deltas and each system was self-sustained.
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Controls and evolution of Fan Delta systems in the Miocene Pohang Basin, SE Korea
Sedimentary Geology, 1995Co-Authors: I. G. Hwang, S. K. Chough, S W Hong, M. Y. ChoeAbstract:Abstract The Miocene Pohang Basin, southeastern Korea, occurs in the eastern part of the NE-SW-trending Yangsan Fault which has experienced right-lateral strike-slip deformation since the Eocene. During the Miocene, however, the strike-slip movement was negligible and instead was under extensional regime. Large-scale drainage systems were developed at the junction between the strike-slip zone and the oblique transfer faults, acting as major sources for coarse-grained sediments. High rate of sediment supply and rapid subsidence of the hanging wall resulted in the progradation of large-scale Gilbert-type Fan Deltas (Doumsan, Duksung and Gohyun systems) which all show a radial distributional pattern. Along the steeply inclined footwall scarps, created by NE-SW-trending faults, the drainage systems were relatively small. Here, low rate of sediment supply formed scree-apron-type (Malgol and Yugye systems) and steep-faced slope-type (Maesan system) Fan Deltas. Based on variations in sedimentary facies and distribution, architecture and overlapping patterns, the Fan Delta systems in the Pohang Basin can be divided into four stages of evolution. During the early stage (Early Miocene), alluvial Fans prograded into shallow-marine setting. In the Doumsan and Duksung systems, high rate of sediment supply and rapid rise of relative sea level resulted in the transformation of shoal-water-type to Gilbert-type foresets. In the Malgol and Maesan systems, rapid sea-level rise accompanied with low rate of sediment supply caused transformation of alluvial Fans to scree-apron-type and steep-faced slope-type Fan Deltas, respectively. In the second stage, subsidence of the hanging wall formed large-scale truncation surfaces in the Doumsan and Duksung Fan Deltas. Coarse-grained sediments were continuously supplied in the Doumsan system, whereas only fine-grained sediments were deposited in the Duksung system. In the Malgol system, sediment supply was almost terminated in this stage. In the third stage (Middle Miocene), sediment supply rate of the Doumsan Fan Delta decreased abruptly and the system was overlain by fine-grained Gilbert-type deposits. The Duksung Fan Delta was overlain by the Maesan and Gohyun systems. The Maesan system prograded further basinward. During the last stage (Late Miocene), sediment supply of the Doumsan and Maesan systems was also terminated and the entire basin was draped by fine-grained biogenic materials (mainly diatoms).
I. G. Hwang - One of the best experts on this subject based on the ideXlab platform.
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The Maesan Fan Delta, Miocene Pohang Basin, SE Korea: architecture and depositional processes of a high‐gradient Fan‐Delta‐fed slope system
Sedimentology, 2000Co-Authors: I. G. Hwang, S. K. ChoughAbstract:The Maesan Fan-Delta-fed slope system in the Miocene Pohang Basin occurs between two Gilbert-type Fan Deltas. Detailed analysis of sedimentary facies and bed geometry reveals that the sequence is represented by 13 sedimentary facies. These facies can be organized into three facies associations, representing distinct depositional environments: alluvial Fan (facies association I), steep-faced slope (facies association II), and basin plain (facies association III). Subaerial debris flows and dense, inertia-dominated currents were transformed into subaqueous sediment gravity flows in steep-faced slope environments. Further downslope, these flows were channelized and formed lobate conglomerate and sandstone bodies at the terminal edge of the channels (or chutes). Interchannel and interlobe areas were dominated by homogeneous mudstone and muddy sandstone, deposited by suspension settling of fine-grained materials. Part of the steep-faced slope deposits experienced large-scale slides and slumps. The chutes/channels, lobes and splays on the steep-faced slope of the Maesan system are similar to those in modern subaqueous coarse-grained Fan-Delta systems.
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the maesan Fan Delta miocene pohang basin se korea architecture and depositional processes of a high gradient Fan Delta fed slope system
Sedimentology, 2000Co-Authors: I. G. Hwang, S. K. ChoughAbstract:The Maesan Fan-Delta-fed slope system in the Miocene Pohang Basin occurs between two Gilbert-type Fan Deltas. Detailed analysis of sedimentary facies and bed geometry reveals that the sequence is represented by 13 sedimentary facies. These facies can be organized into three facies associations, representing distinct depositional environments: alluvial Fan (facies association I), steep-faced slope (facies association II), and basin plain (facies association III). Subaerial debris flows and dense, inertia-dominated currents were transformed into subaqueous sediment gravity flows in steep-faced slope environments. Further downslope, these flows were channelized and formed lobate conglomerate and sandstone bodies at the terminal edge of the channels (or chutes). Interchannel and interlobe areas were dominated by homogeneous mudstone and muddy sandstone, deposited by suspension settling of fine-grained materials. Part of the steep-faced slope deposits experienced large-scale slides and slumps. The chutes/channels, lobes and splays on the steep-faced slope of the Maesan system are similar to those in modern subaqueous coarse-grained Fan-Delta systems.
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provenance of coarse grained detritus in Fan Delta systems miocene pohang basin se korea implications for boundary fault movements
Geosciences Journal, 1998Co-Authors: S W Hong, S. K. Chough, I. G. HwangAbstract:In Fan-Delta systems, contemporary activities of boundary faults can be effectively constrained by tracing coarse-grained detritus. In order to reveal provenance and tectonic activities in the western margin of the Pohang Basin (Miocene), a total of 6000 clasts were examined in four FanDelta systems for composition and compared with probable source rocks in the drainage area. Clasts in the Doumsan, Maesan, and Duksung Fan-Delta systems are dominated by granite, granodiorite, gray mudstone, and sandstone with subordinate amounts of rhyolite, dacite, and tuff. The Malgol FanDelta system comprises silicic volcanics (mainly dacite), red or light gray sandstone, and mudstone. These clasts are similar in composition to the rocks exposed in the drainage area (Cretaceous Banyawol and Kisadong formations and Eocene granite and dacite bodies). The results indicate that strike-slip movements along the basin margin were inactive during the deposition of these Fan Deltas and each system was self-sustained.
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Controls and evolution of Fan Delta systems in the Miocene Pohang Basin, SE Korea
Sedimentary Geology, 1995Co-Authors: I. G. Hwang, S. K. Chough, S W Hong, M. Y. ChoeAbstract:Abstract The Miocene Pohang Basin, southeastern Korea, occurs in the eastern part of the NE-SW-trending Yangsan Fault which has experienced right-lateral strike-slip deformation since the Eocene. During the Miocene, however, the strike-slip movement was negligible and instead was under extensional regime. Large-scale drainage systems were developed at the junction between the strike-slip zone and the oblique transfer faults, acting as major sources for coarse-grained sediments. High rate of sediment supply and rapid subsidence of the hanging wall resulted in the progradation of large-scale Gilbert-type Fan Deltas (Doumsan, Duksung and Gohyun systems) which all show a radial distributional pattern. Along the steeply inclined footwall scarps, created by NE-SW-trending faults, the drainage systems were relatively small. Here, low rate of sediment supply formed scree-apron-type (Malgol and Yugye systems) and steep-faced slope-type (Maesan system) Fan Deltas. Based on variations in sedimentary facies and distribution, architecture and overlapping patterns, the Fan Delta systems in the Pohang Basin can be divided into four stages of evolution. During the early stage (Early Miocene), alluvial Fans prograded into shallow-marine setting. In the Doumsan and Duksung systems, high rate of sediment supply and rapid rise of relative sea level resulted in the transformation of shoal-water-type to Gilbert-type foresets. In the Malgol and Maesan systems, rapid sea-level rise accompanied with low rate of sediment supply caused transformation of alluvial Fans to scree-apron-type and steep-faced slope-type Fan Deltas, respectively. In the second stage, subsidence of the hanging wall formed large-scale truncation surfaces in the Doumsan and Duksung Fan Deltas. Coarse-grained sediments were continuously supplied in the Doumsan system, whereas only fine-grained sediments were deposited in the Duksung system. In the Malgol system, sediment supply was almost terminated in this stage. In the third stage (Middle Miocene), sediment supply rate of the Doumsan Fan Delta decreased abruptly and the system was overlain by fine-grained Gilbert-type deposits. The Duksung Fan Delta was overlain by the Maesan and Gohyun systems. The Maesan system prograded further basinward. During the last stage (Late Miocene), sediment supply of the Doumsan and Maesan systems was also terminated and the entire basin was draped by fine-grained biogenic materials (mainly diatoms).
A A Ekdale - One of the best experts on this subject based on the ideXlab platform.
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trace fossils and paleoenvironmental control of ichnofacies in a late quaternary gravel and loess Fan Delta complex new zealand
Palaeogeography Palaeoclimatology Palaeoecology, 1991Co-Authors: A A Ekdale, D W LewisAbstract:Abstract Remarkably well-preserved trace fossil assemblages of a small, Late Quaternary (> 3000 yr B.P.) Fan Delta complex are exposed in sea cliffs south of Conway Flat, North Canterbury, New Zealand. Marine trace fossils are common and well-preserved in the bar, embayment and proDelta facies, but Deltaic distributary facies contain no trace fossils at all. The preceding paper in this journal ( Lewis and Ekdale, 1991 ) describes the lithofacies and their paleoenvironmental setting in this Fan Delta complex. Common trace fossils include the ichnogenera Anconichnus, Arenicolites, Asterosoma, Cylindrichnus, Diplocraterion, Gordia, Helminthoida, Ophiomorpha, Piscichnus, Planolites and Skolithos . One new ichnogenus ( Arborichnus ), two new ichnospecies ( Arborichnus sparsus and Diplocraterion asymmetrium ), and three informal varieties of Diplocraterion parallelum (var. lingum, arcum and quadrum ) are introduced. Local ichnofacies include (a) low-divsity Anconichnus horizontalis Ichnofacies of densely packed burrows of deposit-feeding animals in shallow-marine, fine-grained sediment of bar and distal embayment facies, (b) high-diversity Diplocraterion parallelum var. lingum Ichnofacies of burrows of suspension-feeding animals in interbedded mud, clean sand and gravelly sand of the bar facies, (c) moderate-diversity Diplocraterion parallelum var. quadrum Ichnofacies in interbedded mud and sand of distal embayment facies, and (d) low-diversity Planolites montanus Ichnofacies of deformed burrows in bioturbated mud of the proDelta facies. In addition, sparse animal escape structures (fugichnia) occur locally in interbedded sand and gravel of the bar facies. The trace fossil associations of the Conway Flat Fan Delta complex are unusual in their excellent state of preservation, and many trace fossils are exposed in full-three-dimensional relief. Because of their very young age, they must reflect similar associations of biogenic sedimentary structures in modern Deltaic settings that are as yet undescribed. This report appears to be the first documentation of a fully marine trace fossil assemblage in loessial sediments.
Jesus Reolid - One of the best experts on this subject based on the ideXlab platform.
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palaeoenvironmental interpretation of the pliocene Fan Delta system of the vera basin se spain fossil assemblages ichnology and taphonomy
Palaeoworld, 2020Co-Authors: Joaquin Sendra, Matias Reolid, Jesus ReolidAbstract:Abstract The marine fossil assemblages of the Pliocene of south Spain constitute the record of the marine fauna that colonised the western part of the Mediterranean after the Messinian Salinity Crisis. This work focuses on the analysis of lithofacies and fossil assemblages including trace fossils, invertebrates, and vertebrates with special attention to taphonomic features, for interpreting palaeoenvironmental conditions in the Vera Basin (SE Spain). The sedimentary sequences of the northern region of the Vera Basin display diverse stratigraphical, sedimentological, and palaeontological features that correspond to the evolution of a Fan-Delta in a narrow basin. The Vera Basin was characterised by shallow-marine shelf conditions during the early-mid Pliocene (Cuevas Formation). The basin emergence with the development of Gilbert-type Fan Deltas (Vera Member), and a protected, partially-enclosed marine embayment (Almanzora Member) occurred during the mid-late Pliocene due to regional uplift and movements of the Palomares strike-slip Fault along the eastern basin margin. The progradation of the central Fan-Delta lobes and the interaction with marginal Fan-Delta resulted in the partitioning of the basin that formed a small sub-basin with restricted stagnant conditions that favoured a Konservat Fossil-Lagerstatte. The high input of siliciclasts due to the uplift context of the margins of the basin favoured a high sedimentation rate and the fast burial of vertebrate remains. Fossil marine mammals occurs from shallow shelf deposits (Cuevas Formation) to bottomset (Cuevas Formation-Vera Member transition) and lower part of the clinoforms in the foreset (Vera Member). Cetacean remains are usually recorded not only in the relatively deep-water silty marls and sandy marls of the outer shelf and distal facies of the Fan-Delta (Espiritu Santo Formation), but also in the shallower coarse sands and conglomerates (Cuevas Formation and Espiritu Santo Formation). Sirenian remains, in contrast, are only recorded in coarse sand facies (Cuevas Formation and Espiritu Santo Formation) associated to charcoal wood fragments deposited in shallow waters near the shoreline. This narrow and relatively protected basin is interpreted as an area of reproduction and nursery of juveniles on the basis of the presence of cetaceans.
