J. Counts, Madeleine L. Vickers, M. R. Stokes, W. Spivey, Kristina F. Gardner, J. Self‐Trail, J. Gooley, Ryan J. McAleer, Aaron Jubb, D. Houseknecht, R. Lease, Neil P. Griffis, Martin Vickers, K. Śliwińska, H. Tompkins, Adam M. Hudson
The type locality for the upper Oligocene Nuwok Member of the Sagavanirktok Formation (Carter Creek, North Slope, Alaska, USA) contains abundant occurrence of glendonite, a pseudomorph after the calcium carbonate mineral ikaite, which typically forms in the shallow subsurface of cold marine sediments. The region during the time of Nuwok Member deposition was located at a high latitude, similar to today, and the study site is characterized by sands and silty muds interpreted here to have been deposited in coastal and shelfal marine environments. Isotopic (Sr) and biostratigraphic (foraminifera) evidence presented here refine the depositional age of the outcrop to approximately 24 Ma. Glendonites occur in two basic forms: radial clusters, commonly centered around a single larger primary crystal ( approx. 10 cm; Type A) and larger single blades generally without accessory crystals (approx. 15–25 cm; Type B). Microscopic examination revealed a sequence of multiple types of replacive calcite that formed as a direct result of ikaite transformation: Type 1 rhombohedral crystals characterized by microporous and inclusion-rich cores and concentric zones, Type 2A, composed of clear calcite that overgrew and augmented Type 1 crystals, and inclusion-rich, microcrystalline Type 2B, which formed a matrix surrounding the rhombs and commonly dominates the outer rims of glendonite specimens. Type 3 calcite precipitated as fibrous, botryoidal epitaxial cement atop previous phases and is not ikaite-derived. These phases are distributed in similar ways in all examined specimens and are consistent with several previously described glendonite occurrences around the world, despite differing diagenetic and geologic histories. Stable isotope evidence (δ13C and δ18O) suggests sourcing of glendonite carbon from both organic and methanogenic sources. Glendonites of the Nuwok Member can therefore assist in the determination of a more comprehensive ikaite transformation model, improving our understanding of glendonite formation and the sedimentological and environmental context of their occurrence. Oligocene glendonites are uncommon globally; the well-preserved occurrence described here can allow future studies to better reconstruct Arctic environmental conditions and paleoclimates during this time.
上渐新统Sagavanirktok组Nuwok段(Carter Creek, North Slope, Alaska, USA)的类型位置富含绿榴石，这是一种继碳酸钙矿物ikaite之后的伪形态，通常形成于寒冷海洋沉积物的浅层次表层。Nuwok成员沉积时期的地区位于高纬度地区，与今天相似，研究地点的特点是沙子和粉质泥浆，在这里被解释为沉积在沿海和陆架海洋环境中。这里提出的同位素(Sr)和生物地层(有孔虫)证据将露头的沉积时代确定为大约24 Ma。绿橄榄石以两种基本形式出现:放射状簇状，通常以一个较大的原生晶体为中心。10厘米;A型)和更大的单叶片，通常没有附属晶体(大约。15 - 25厘米;镜下检查发现一系列由爱凯石转变直接形成的多种类型的替代方解石:1型方解石以微孔和富含包裹体的岩心和同心区为特征;2A型方解石由透明方解石组成，过度生长和增强了1型晶体;2B型方解石由富含包裹体的微晶组成，形成了包围方解石的基质，通常主导着绿榴石标本的外缘。3型方解石以纤维状、瓶状外延水泥的形式沉淀于前相之上，并非由岩矿衍生。尽管成岩和地质历史不同，但这些阶段在所有被检查的标本中以相似的方式分布，并且与世界各地先前描述的几处绿榴石矿床一致。稳定同位素证据(δ13C和δ18O)表明绿榴石碳的来源既有有机碳源，也有甲烷碳源。因此，Nuwok段的格兰东岩可以帮助确定一个更全面的艾克岩转化模式，提高我们对格兰东岩形成及其发生的沉积学和环境背景的理解。渐新世榴辉岩在全球并不常见;这里描述的保存完好的事件可以让未来的研究更好地重建这一时期的北极环境条件和古气候。
{"title":"Insights into glendonite formation from the upper Oligocene Sagavanirktok Formation, North Slope, Alaska","authors":"J. Counts, Madeleine L. Vickers, M. R. Stokes, W. Spivey, Kristina F. Gardner, J. Self‐Trail, J. Gooley, Ryan J. McAleer, Aaron Jubb, D. Houseknecht, R. Lease, Neil P. Griffis, Martin Vickers, K. Śliwińska, H. Tompkins, Adam M. Hudson","doi":"10.2110/jsr.2023.060","DOIUrl":"https://doi.org/10.2110/jsr.2023.060","url":null,"abstract":"The type locality for the upper Oligocene Nuwok Member of the Sagavanirktok Formation (Carter Creek, North Slope, Alaska, USA) contains abundant occurrence of glendonite, a pseudomorph after the calcium carbonate mineral ikaite, which typically forms in the shallow subsurface of cold marine sediments. The region during the time of Nuwok Member deposition was located at a high latitude, similar to today, and the study site is characterized by sands and silty muds interpreted here to have been deposited in coastal and shelfal marine environments. Isotopic (Sr) and biostratigraphic (foraminifera) evidence presented here refine the depositional age of the outcrop to approximately 24 Ma. Glendonites occur in two basic forms: radial clusters, commonly centered around a single larger primary crystal ( approx. 10 cm; Type A) and larger single blades generally without accessory crystals (approx. 15–25 cm; Type B). Microscopic examination revealed a sequence of multiple types of replacive calcite that formed as a direct result of ikaite transformation: Type 1 rhombohedral crystals characterized by microporous and inclusion-rich cores and concentric zones, Type 2A, composed of clear calcite that overgrew and augmented Type 1 crystals, and inclusion-rich, microcrystalline Type 2B, which formed a matrix surrounding the rhombs and commonly dominates the outer rims of glendonite specimens. Type 3 calcite precipitated as fibrous, botryoidal epitaxial cement atop previous phases and is not ikaite-derived. These phases are distributed in similar ways in all examined specimens and are consistent with several previously described glendonite occurrences around the world, despite differing diagenetic and geologic histories. Stable isotope evidence (δ13C and δ18O) suggests sourcing of glendonite carbon from both organic and methanogenic sources. Glendonites of the Nuwok Member can therefore assist in the determination of a more comprehensive ikaite transformation model, improving our understanding of glendonite formation and the sedimentological and environmental context of their occurrence. Oligocene glendonites are uncommon globally; the well-preserved occurrence described here can allow future studies to better reconstruct Arctic environmental conditions and paleoclimates during this time.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138625018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Mclaurin, Dirk Goossens, Brenda J. Buck, Wanda Taylor
Lacustrine basins and the sediments within them provide a critical component of regional tectonic development and climate history. Each sub-basin in the landscape records the interplay between active tectonism and shifting climate. Many of the basins in southern Nevada that contain deposits of the Muddy Creek Formation were closed fluvio-lacustrine systems during the latest Miocene and into the Pliocene. They were subsequently integrated into the regional Colorado River system. Lacustrine deposits of the Muddy Creek Formation are exposed along the trace of the Las Vegas Valley shear zone in the Nellis Dunes Recreation Area (NDRA), northeast of Las Vegas, NV. The Muddy Creek Formation in NDRA consists of approximately 130 m of mixed carbonates and clastics, and new tephrochronology suggests an early to late Pliocene age (about 4.7 to about 2.6 Ma) for the lowermost lacustrine deposits and an unknown, but younger age for the uppermost spring-fed lacustrine deposit. These sediments were deposited in an arid to semi-arid lake (Lake Nellis) and alluvial floodplain system based on the interpretation of lithologies and facies associations. The stratigraphic succession coarsens upward and reflects establishment of a lacustrine carbonate system overlain by a clastic succession of peripheral lake sediments of alluvial and floodplain origin. The peripheral lake deposits consist of spring-fed and fluvial wetland mudflats of brown claystone and siltstone. This brown claystone is capped by a succession of yellow and red sandstones deposited by fluvial and minor eolian processes. The second, and youngest freshwater limestone, likely disconformably, overlies the yellow and r ed sandstones, and is thought to be temporally and depositionally distinct from the underlying Muddy Creek deposits. The transition from the lower lacustrine carbonates to clastic fluvial channel and flood plain deposits indicates desiccation of Lake Nellis and possibly occurs soon after about 2.7 to about 2.6 Ma based on the ages of tuffs occurring within the uppermost limestone and marl beds. This is consistent with an interpreted increase in regional aridity after approximately 2.8 Ma (Smith et al. 1993). The second limestone deposit at the top of the section represents an even younger spring/lacustrine deposit of unknown age. Throughout the lower carbonate section, three tuffs were identified, and geochemically correlated, using a discriminant function analysis, to the tuff of Napa (≤ 4.70 ± 0.03 Ma), the Putah Tuff (about 3.3 Ma) and the lower tuffs of the Badlands ( about 2.7 – about 2.6 Ma). The timing of deposition of Lake Nellis sediments post-dates the integration of the three major lake syste ms in this region (Lake Grand Wash, Lake Hualapai, and Lake Las Vegas) into the Colorado River drainage (5.6 – 4.9 Ma), and also postdates the full integration of the river to sea level (4.8 - 4.63 Ma) (Howard et al. 2015; Crow et al. 2021). Lake Nellis represents an isolated lake basin that
{"title":"Pliocene lacustrine system in the Nellis basin, southern Nevada: implications for the Colorado River drainage system","authors":"B. Mclaurin, Dirk Goossens, Brenda J. Buck, Wanda Taylor","doi":"10.2110/jsr.2022.116","DOIUrl":"https://doi.org/10.2110/jsr.2022.116","url":null,"abstract":"Lacustrine basins and the sediments within them provide a critical component of regional tectonic development and climate history. Each sub-basin in the landscape records the interplay between active tectonism and shifting climate. Many of the basins in southern Nevada that contain deposits of the Muddy Creek Formation were closed fluvio-lacustrine systems during the latest Miocene and into the Pliocene. They were subsequently integrated into the regional Colorado River system. Lacustrine deposits of the Muddy Creek Formation are exposed along the trace of the Las Vegas Valley shear zone in the Nellis Dunes Recreation Area (NDRA), northeast of Las Vegas, NV. The Muddy Creek Formation in NDRA consists of approximately 130 m of mixed carbonates and clastics, and new tephrochronology suggests an early to late Pliocene age (about 4.7 to about 2.6 Ma) for the lowermost lacustrine deposits and an unknown, but younger age for the uppermost spring-fed lacustrine deposit. These sediments were deposited in an arid to semi-arid lake (Lake Nellis) and alluvial floodplain system based on the interpretation of lithologies and facies associations. The stratigraphic succession coarsens upward and reflects establishment of a lacustrine carbonate system overlain by a clastic succession of peripheral lake sediments of alluvial and floodplain origin. The peripheral lake deposits consist of spring-fed and fluvial wetland mudflats of brown claystone and siltstone. This brown claystone is capped by a succession of yellow and red sandstones deposited by fluvial and minor eolian processes. The second, and youngest freshwater limestone, likely disconformably, overlies the yellow and r ed sandstones, and is thought to be temporally and depositionally distinct from the underlying Muddy Creek deposits. The transition from the lower lacustrine carbonates to clastic fluvial channel and flood plain deposits indicates desiccation of Lake Nellis and possibly occurs soon after about 2.7 to about 2.6 Ma based on the ages of tuffs occurring within the uppermost limestone and marl beds. This is consistent with an interpreted increase in regional aridity after approximately 2.8 Ma (Smith et al. 1993). The second limestone deposit at the top of the section represents an even younger spring/lacustrine deposit of unknown age. Throughout the lower carbonate section, three tuffs were identified, and geochemically correlated, using a discriminant function analysis, to the tuff of Napa (≤ 4.70 ± 0.03 Ma), the Putah Tuff (about 3.3 Ma) and the lower tuffs of the Badlands ( about 2.7 – about 2.6 Ma). The timing of deposition of Lake Nellis sediments post-dates the integration of the three major lake syste ms in this region (Lake Grand Wash, Lake Hualapai, and Lake Las Vegas) into the Colorado River drainage (5.6 – 4.9 Ma), and also postdates the full integration of the river to sea level (4.8 - 4.63 Ma) (Howard et al. 2015; Crow et al. 2021). Lake Nellis represents an isolated lake basin that ","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139199052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cecilia A. Benavente, Kevin M. Bohacs, Adriana C. Mancuso
The Santa Clara Abajo and Santa Clara Arriba formations host a diverse assemblage of trace fossils that record a wide range of behaviors and a broad array of ecological niches during the Middle Triassic, a critical period in the evolution of continental fauna with the diversification of both synapsids (cynodont and dicynodont) and archosauromorphs (dinosaurs, pterosaurs, and crocodilians) that represent post-Permian faunal recovery. The Santa Clara formations are part of the continental infill of the Cuyana rift Basin in Argentina and represent a lacustrine system with fluvial input and delta development. Sedimentological characteristics of these units as well as their stacking patterns characterize a “fluctuating profundal” facies association typical of a balanced-fill lake basin. The lacustrine and associated terrestrial environments preserve a rich record of invertebrate traces with 26 ichnogenera from ethological classes of fodichnia, domichnia, repichnia, pascichnia, and cubichnia occupying all co ntinental tiers (subaerial and subaqueous, surficial/very shallow, shallow, mid, and deeper) and ecological niches (epiterraphilic, terraphilic, hygrophilic, and hydrophilic). In association with the invertebrate traces, two taphonomic modes of tetrapod footprints have been found: a moderate fidelity mode and a high fidelity mode. Physical sedimentary features, burrows, trails, and tracks, and their stratigraphic positions are integrated to interpret the main factors involved in footprint preservation in these subsettings. The most significant and variable preservational factor found is water-table fluctuations controlled by the paleohydrology of a balanced-fill lake system. These data show that in balanced-fill lake systems, diverse trace assemblages occur in the lake and associated subsettings such as delta plains, and lake-margin settings whereas trace fossils can be totally absent in coeval lake-center strata, particularly if anoxic lake bottom conditions occur, as probably occurred in the meromictic Santa Clara lake system.
{"title":"Interpreted depositional conditions of balanced-fill lake basin strata incorporating vertebrate and invertebrate trace fossils, Triassic Santa Clara Sub-Basin, Cuyana Rift Basin, Argentina","authors":"Cecilia A. Benavente, Kevin M. Bohacs, Adriana C. Mancuso","doi":"10.2110/jsr.2021.124","DOIUrl":"https://doi.org/10.2110/jsr.2021.124","url":null,"abstract":"The Santa Clara Abajo and Santa Clara Arriba formations host a diverse assemblage of trace fossils that record a wide range of behaviors and a broad array of ecological niches during the Middle Triassic, a critical period in the evolution of continental fauna with the diversification of both synapsids (cynodont and dicynodont) and archosauromorphs (dinosaurs, pterosaurs, and crocodilians) that represent post-Permian faunal recovery. The Santa Clara formations are part of the continental infill of the Cuyana rift Basin in Argentina and represent a lacustrine system with fluvial input and delta development. Sedimentological characteristics of these units as well as their stacking patterns characterize a “fluctuating profundal” facies association typical of a balanced-fill lake basin. The lacustrine and associated terrestrial environments preserve a rich record of invertebrate traces with 26 ichnogenera from ethological classes of fodichnia, domichnia, repichnia, pascichnia, and cubichnia occupying all co ntinental tiers (subaerial and subaqueous, surficial/very shallow, shallow, mid, and deeper) and ecological niches (epiterraphilic, terraphilic, hygrophilic, and hydrophilic). In association with the invertebrate traces, two taphonomic modes of tetrapod footprints have been found: a moderate fidelity mode and a high fidelity mode. Physical sedimentary features, burrows, trails, and tracks, and their stratigraphic positions are integrated to interpret the main factors involved in footprint preservation in these subsettings. The most significant and variable preservational factor found is water-table fluctuations controlled by the paleohydrology of a balanced-fill lake system. These data show that in balanced-fill lake systems, diverse trace assemblages occur in the lake and associated subsettings such as delta plains, and lake-margin settings whereas trace fossils can be totally absent in coeval lake-center strata, particularly if anoxic lake bottom conditions occur, as probably occurred in the meromictic Santa Clara lake system.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136281615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The ammonites in spherical carbonate concretions often preserve their original three-dimensional (3D) shell shapes and detailed fragile structures. However, the formation process of spherical ammonite concretion is not fully understood. Herein, the ammonite concretions identified in the Cretaceous (Campanian) Osoushinai Formation, Yezo Group, Japan, are examined to understand their formation process during the soft tissue decomposition after burial in marine sediments. In the Osoushinai Formation, almost all observed ammonites in concretions preserve their 3D form without phragmocone deformation. The calcite filling in the remaining body chamber of ammonites (BC1) shows that shells were buried with soft tissues. These occurrences, negative delta13C values, and the near-zero delta18O values of BC1 as well as the concretions indicate that both BC1 and concretions rapidly formed from dissolved inorganic carbon derived from organic matter, including the soft tissue of dead organisms, in the shallow part of the sediments. The increasing Fe concentration in BC1 shows that BC1 formed in the iron reduction (FeR) zone, where organic matter was decomposed owing to the activity of iron-reducing microorganisms. The similarity of the elemental and isotopic compositions of BC1 and concretions show that they concurrently formed in the FeR zone. In the Osoushinai Formation, an abundant influx of Fe(III) and intense bioturbation during the deposition of the formation promoted organic decomposition in the FeR zone, causing rapid formation of BC1 and concretions. Such rapidly formed calcite fillings and concretions protected fossils from deformation and dissolution during diagenesis to preserve their 3D form. Overall, the findings of this study provide a new insight into the relation between sedimentary environments and the fossil preservation process via rapid concretion formation.
{"title":"Ammonite concretion formation through organic decomposition in the iron reduction zone","authors":"Yusuke Muramiya, Hidekazu Yoshida, Nagayoshi Katsuta, Ryusei Kuma, Tomoyuki Mikami","doi":"10.2110/jsr.2023.078","DOIUrl":"https://doi.org/10.2110/jsr.2023.078","url":null,"abstract":"The ammonites in spherical carbonate concretions often preserve their original three-dimensional (3D) shell shapes and detailed fragile structures. However, the formation process of spherical ammonite concretion is not fully understood. Herein, the ammonite concretions identified in the Cretaceous (Campanian) Osoushinai Formation, Yezo Group, Japan, are examined to understand their formation process during the soft tissue decomposition after burial in marine sediments. In the Osoushinai Formation, almost all observed ammonites in concretions preserve their 3D form without phragmocone deformation. The calcite filling in the remaining body chamber of ammonites (BC1) shows that shells were buried with soft tissues. These occurrences, negative delta13C values, and the near-zero delta18O values of BC1 as well as the concretions indicate that both BC1 and concretions rapidly formed from dissolved inorganic carbon derived from organic matter, including the soft tissue of dead organisms, in the shallow part of the sediments. The increasing Fe concentration in BC1 shows that BC1 formed in the iron reduction (FeR) zone, where organic matter was decomposed owing to the activity of iron-reducing microorganisms. The similarity of the elemental and isotopic compositions of BC1 and concretions show that they concurrently formed in the FeR zone. In the Osoushinai Formation, an abundant influx of Fe(III) and intense bioturbation during the deposition of the formation promoted organic decomposition in the FeR zone, causing rapid formation of BC1 and concretions. Such rapidly formed calcite fillings and concretions protected fossils from deformation and dissolution during diagenesis to preserve their 3D form. Overall, the findings of this study provide a new insight into the relation between sedimentary environments and the fossil preservation process via rapid concretion formation.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136281749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Perkey, S. J. Smith, Kelsey A. Fall, Danielle R.N. Tarpley, Carl T. Freidrichs
Flume based research has demonstrated that large (greater than 1mm), high water content mud aggregates can be eroded from cohesive beds and transported in bedload. Studies have also documented these types of mud clasts preserved in the lithologic record. However, questions pertaining to the abundance of muddy bed aggregates and the physical properties that result in their production remain largely unaddressed. New flume experiments were conducted on materials from numerous sediment management project locations across the United States. Image analysis of eroded sediment particles demonstrated that macro-aggregated (greater than 250 microns) mud clasts were commonly produced in moderately consolidated sediment beds (1.2 g/cm3 -1.5 g/cm3) with water content above the plastic limit. These macro-aggregates commonly accounted for more than 20% of the total eroded sediment mass. Physical properties commonly associated with cohesive behavior were evaluated for correlation to bed aggregate production and size. Clay content of the sediment bed was shown to have the greatest correlation to both macro-aggregate size and abundance.
{"title":"Production and Abundance of Macro-Aggregate Bed Clasts from Moderately Consolidated Cohesive Beds and their implications for Sediment Management","authors":"D. Perkey, S. J. Smith, Kelsey A. Fall, Danielle R.N. Tarpley, Carl T. Freidrichs","doi":"10.2110/jsr.2023.040","DOIUrl":"https://doi.org/10.2110/jsr.2023.040","url":null,"abstract":"Flume based research has demonstrated that large (greater than 1mm), high water content mud aggregates can be eroded from cohesive beds and transported in bedload. Studies have also documented these types of mud clasts preserved in the lithologic record. However, questions pertaining to the abundance of muddy bed aggregates and the physical properties that result in their production remain largely unaddressed. New flume experiments were conducted on materials from numerous sediment management project locations across the United States. Image analysis of eroded sediment particles demonstrated that macro-aggregated (greater than 250 microns) mud clasts were commonly produced in moderately consolidated sediment beds (1.2 g/cm3 -1.5 g/cm3) with water content above the plastic limit. These macro-aggregates commonly accounted for more than 20% of the total eroded sediment mass. Physical properties commonly associated with cohesive behavior were evaluated for correlation to bed aggregate production and size. Clay content of the sediment bed was shown to have the greatest correlation to both macro-aggregate size and abundance.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139290313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Martin R. Gibling, Ruofei Jia, Robert A. Gastaldo, Johann Neveling, Heriberto Rochín-Bañaga
The Triassic Katberg Formation has played a central role in interpreting the end-Permian ecosystem crisis, as part of a hypothesis of aridification, vegetation loss, and sediment release in continental settings. We use drone images of an inaccessible cliff near Bethulie to investigate the Swartberg member, a braided-fluvial body 45 m thick, describing remote outcrop facies to identify geomorphic units and using spatial analysis to estimate their proportions in 2-D sections. Here the Swartberg member comprises three channel belts within shallow valleys, the lowermost of which is ∼500 m wide and incised into lacustrine deposits. The component channel bodies consist mainly of trough cross-bedded sand sheets (48%) and channel-scour fills (28%). Recognizable bars (15%) comprise unit bars with high-angle slipfaces and mounded bar cores (components of mid-channel compound bars), bars built around vegetation, and bank-attached bars in discrete, probably low-sinuosity conduits. Abandoned channels constitute 8% and 16% of flow-parallel and -transverse sections, respectively. When corrected for compaction, the average thalweg depth of the larger channels is 3.9 m, with an average bankfull width of 84 m, scaling broadly with the relief of the bars and comparable in scale to the Platte and South Saskatchewan rivers of North America. The fluvial style implies perennial but seasonably variable flow in a vegetated landscape with a humid paleoclimate. The northward paleoflow accords with regional paleoflow patterns and deposition on a megafan sourced in the Cape Fold Belt, where the Swartberg member represents the avulsion of a major transverse-flowing river.U-Pb dating of in situ and reworked pedogenic carbonate nodules from below the base of the Swartberg member yielded Anisian to Ladinian ages (Middle Triassic), younger than the previously assumed Early Triassic age and implying that considerable gaps in time exist in the succession. An assessment of the interval spanning the lower to mid Katberg Formation is needed to reevaluate the inferred unidirectional trend in fluvial style, aridification, and fossil distributions in this condensed, disjunct succession.
{"title":"BRAIDED-RIVER ARCHITECTURE OF THE TRIASSIC SWARTBERG MEMBER, KATBERG FORMATION, SOUTH AFRICA: ASSESSING AGE, FLUVIAL STYLE, AND PALEOCLIMATE AFTER THE END-PERMIAN EXTINCTION","authors":"Martin R. Gibling, Ruofei Jia, Robert A. Gastaldo, Johann Neveling, Heriberto Rochín-Bañaga","doi":"10.2110/jsr.2023.018","DOIUrl":"https://doi.org/10.2110/jsr.2023.018","url":null,"abstract":"The Triassic Katberg Formation has played a central role in interpreting the end-Permian ecosystem crisis, as part of a hypothesis of aridification, vegetation loss, and sediment release in continental settings. We use drone images of an inaccessible cliff near Bethulie to investigate the Swartberg member, a braided-fluvial body 45 m thick, describing remote outcrop facies to identify geomorphic units and using spatial analysis to estimate their proportions in 2-D sections. Here the Swartberg member comprises three channel belts within shallow valleys, the lowermost of which is ∼500 m wide and incised into lacustrine deposits. The component channel bodies consist mainly of trough cross-bedded sand sheets (48%) and channel-scour fills (28%). Recognizable bars (15%) comprise unit bars with high-angle slipfaces and mounded bar cores (components of mid-channel compound bars), bars built around vegetation, and bank-attached bars in discrete, probably low-sinuosity conduits. Abandoned channels constitute 8% and 16% of flow-parallel and -transverse sections, respectively. When corrected for compaction, the average thalweg depth of the larger channels is 3.9 m, with an average bankfull width of 84 m, scaling broadly with the relief of the bars and comparable in scale to the Platte and South Saskatchewan rivers of North America. The fluvial style implies perennial but seasonably variable flow in a vegetated landscape with a humid paleoclimate. The northward paleoflow accords with regional paleoflow patterns and deposition on a megafan sourced in the Cape Fold Belt, where the Swartberg member represents the avulsion of a major transverse-flowing river.U-Pb dating of in situ and reworked pedogenic carbonate nodules from below the base of the Swartberg member yielded Anisian to Ladinian ages (Middle Triassic), younger than the previously assumed Early Triassic age and implying that considerable gaps in time exist in the succession. An assessment of the interval spanning the lower to mid Katberg Formation is needed to reevaluate the inferred unidirectional trend in fluvial style, aridification, and fossil distributions in this condensed, disjunct succession.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138509999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
John Menzies, Roger C. Paulen, Jürgen M. Reitner, Cunhai Gao, Tyler Hodder, Martin Ross
Abstract Subglacial sediments are subject to erosion, transport, and deposition in active, ephemeral, and spatially localized glacial environments. It is critical to determine how these mobilized sediments become immobilized in a time-transgressive process and can be frequently remobilized and reimmobilized. Microscopic sedimentary structural signatures provide invaluable information on subglacial processes and contribute to understanding till formation. Data were obtained from a series of field sites in Canada and Austria investigating the microsedimentological aspects of both alpine and continental glaciation tills to construct a conceptual model of subglacial deformation. Microstructures in these tills indicate rheological behaviors that can be summarized into a potential model for soft deforming subglacial sediments. Most microstructures noted in these subglacial till examples highlight the development of subglacial interface kinematics providing clues to till deposition mechanics, subglacial bedform development, and the processes involved in till provenance distributions. A conceptual process model of subglacial interface conditions in soft mobile sediments is developed that uses microsedimentological evidence and highlights how an active ice mass integrates with ongoing substrate deformation. In the model, interaction occurs between the ice and its sediment bed with internal sediment microstructures evolving where multiple transient shear deformation processes cause localized deformation linked to pervasive and nonpervasive sediment deformation.
{"title":"Subglacial tills: a process model based on microsedimentological clues","authors":"John Menzies, Roger C. Paulen, Jürgen M. Reitner, Cunhai Gao, Tyler Hodder, Martin Ross","doi":"10.2110/jsr.2022.017","DOIUrl":"https://doi.org/10.2110/jsr.2022.017","url":null,"abstract":"Abstract Subglacial sediments are subject to erosion, transport, and deposition in active, ephemeral, and spatially localized glacial environments. It is critical to determine how these mobilized sediments become immobilized in a time-transgressive process and can be frequently remobilized and reimmobilized. Microscopic sedimentary structural signatures provide invaluable information on subglacial processes and contribute to understanding till formation. Data were obtained from a series of field sites in Canada and Austria investigating the microsedimentological aspects of both alpine and continental glaciation tills to construct a conceptual model of subglacial deformation. Microstructures in these tills indicate rheological behaviors that can be summarized into a potential model for soft deforming subglacial sediments. Most microstructures noted in these subglacial till examples highlight the development of subglacial interface kinematics providing clues to till deposition mechanics, subglacial bedform development, and the processes involved in till provenance distributions. A conceptual process model of subglacial interface conditions in soft mobile sediments is developed that uses microsedimentological evidence and highlights how an active ice mass integrates with ongoing substrate deformation. In the model, interaction occurs between the ice and its sediment bed with internal sediment microstructures evolving where multiple transient shear deformation processes cause localized deformation linked to pervasive and nonpervasive sediment deformation.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136376981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O.A. Prasojo, A.E van Yperen, T.B. Hoey, A. Owen, R. Williams
Quantifying paleodischarge from geological field observations remains a key research challenge. Several scaling relationships between paleodischarge and channel morphology (width; depth) have been developed for rivers and river deltas. Previous paleodischarge scaling relationships were based on discharge-catchment area scaling and an empirical flow velocity estimate (e.g. Chézy, Manning formulae) multiplied by channel cross-sectional area to derive discharge. In deltas, where marine (wave, tide) energy causes bidirectional flow within distributary channels, the available paleodischarge scaling relationships are not applicable due to their unidirectional flow assumption. Here, the spatial variability of distributary channel widths from a database of 114 global modern river deltas is assessed to understand the limit of marine influence on distributary channel widths. Using 6213 distributary channel width measurements, the median channel widths of distributary channels for each delta were correlated with bankfull discharge for river-, tide- and wave-dominated deltas, the latter two including the effect of bidirectional flow. Statistically significant width-discharge scaling relationships are derived for river- and wave-dominated deltas, with no significant relationships identified for tide-dominated deltas. By reverse bootstrapping the channel widths measured from modern deltas, the minimum number of width measurements needed to apply width-discharge scaling relationships to ancient deltaic deposits is estimated as 3 and 4 for the upstream parts of river- and wave-dominated deltas, respectively, increasing to 30 in the downstream parts of river-dominated deltas. These estimates will guide sedimentological studies that often have limited numbers of distributary channel widths exposed in the rock record. To test the reliability of these alternative width-discharge scaling relationships in the rock record, paleodischarges were estimated for the well-studied Cretaceous lower Mesa Rica Sandstone Formation, USA . Comparison of these results with the more complex Chézy-derived method suggests that these new scaling relationships are accurate. Hence, it is proposed that the scaling relationships obtained from modern deltas can be applied to the rock record, requiring fewer, and easier to measure, data inputs than previously published methods.
{"title":"Using delta channel width to estimate paleodischarge in the rock record: geometric scaling and practical sampling criteria","authors":"O.A. Prasojo, A.E van Yperen, T.B. Hoey, A. Owen, R. Williams","doi":"10.2110/jsr.2022.057","DOIUrl":"https://doi.org/10.2110/jsr.2022.057","url":null,"abstract":"Quantifying paleodischarge from geological field observations remains a key research challenge. Several scaling relationships between paleodischarge and channel morphology (width; depth) have been developed for rivers and river deltas. Previous paleodischarge scaling relationships were based on discharge-catchment area scaling and an empirical flow velocity estimate (e.g. Chézy, Manning formulae) multiplied by channel cross-sectional area to derive discharge. In deltas, where marine (wave, tide) energy causes bidirectional flow within distributary channels, the available paleodischarge scaling relationships are not applicable due to their unidirectional flow assumption. Here, the spatial variability of distributary channel widths from a database of 114 global modern river deltas is assessed to understand the limit of marine influence on distributary channel widths. Using 6213 distributary channel width measurements, the median channel widths of distributary channels for each delta were correlated with bankfull discharge for river-, tide- and wave-dominated deltas, the latter two including the effect of bidirectional flow. Statistically significant width-discharge scaling relationships are derived for river- and wave-dominated deltas, with no significant relationships identified for tide-dominated deltas. By reverse bootstrapping the channel widths measured from modern deltas, the minimum number of width measurements needed to apply width-discharge scaling relationships to ancient deltaic deposits is estimated as 3 and 4 for the upstream parts of river- and wave-dominated deltas, respectively, increasing to 30 in the downstream parts of river-dominated deltas. These estimates will guide sedimentological studies that often have limited numbers of distributary channel widths exposed in the rock record. To test the reliability of these alternative width-discharge scaling relationships in the rock record, paleodischarges were estimated for the well-studied Cretaceous lower Mesa Rica Sandstone Formation, USA . Comparison of these results with the more complex Chézy-derived method suggests that these new scaling relationships are accurate. Hence, it is proposed that the scaling relationships obtained from modern deltas can be applied to the rock record, requiring fewer, and easier to measure, data inputs than previously published methods.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135216891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shale diagenesis is not well understood, and the cracks in shale contain important information about the diagenetic conditions. The way these cracks open reveals physical changes in the sediment, and the infilling minerals provide insight into the chemical conditions of the formation water. Typically, the authigenic minerals filling the folded cracks are consistent with the chemical composition of the host rocks. For example, folded calcite cracks are found in limestone. This paper, however, focuses on a set of folded calcite cracks in non-calcareous black shales. The goal is to improve our understanding of shale diagenesis by deciphering the origins of these cracks. The cracks are sinuously to ptygmatically folded in a vertical view and weakly sinuous on the bedding plane. They are filled with calcite, bitumen, pyrite, or a combination of them. Evidence of bioturbation and low redox-sensitive trace elemental ratios suggest suboxic to oxic depositional conditions of the shale. The cracks were likely op ened by gas expansion in the unconsolidated mud. The main mineral filling the cracks, calcite, was sourced from hydrothermal fluid that passed through the underlying dolomite. Hydrothermal influences are indicated by the presence of bornite and microcrystalline pyrite in the cracks, as well as Fe and Mn enrichment in the host sediments. Hydrothermal activity can also explain the presence of buddingtonite, an ammonium feldspar in the shale. The results of this study suggest that folded cracks filled by minerals, gradually narrowing towards the top, and lacking internal detrital matrix are likely formed during early diagenesis. The inconsistency between the chemical compositions of the infilling material and the host sediment requires further exploration to identify the source. Hydrothermal fluid passing through the underlying dolomite may be the source of folded calcite cracks in non-calcareous sedimentary rocks. These cracks resemble molar-tooth structures (MTS), which are sinuous cracks filled with micro crystalline calcite mostly found in Precambrian limestone and calcareous shales. If these cracks are indeed MTS, they may be an exception to the age and host-rock lithology constraints of MTS.
{"title":"Folded calcite cracks in non-calcareous shales: a window into shale diagenesis and hydrothermal influence","authors":"Sun Bin, Yang Wan","doi":"10.2110/jsr.2023.024","DOIUrl":"https://doi.org/10.2110/jsr.2023.024","url":null,"abstract":"Shale diagenesis is not well understood, and the cracks in shale contain important information about the diagenetic conditions. The way these cracks open reveals physical changes in the sediment, and the infilling minerals provide insight into the chemical conditions of the formation water. Typically, the authigenic minerals filling the folded cracks are consistent with the chemical composition of the host rocks. For example, folded calcite cracks are found in limestone. This paper, however, focuses on a set of folded calcite cracks in non-calcareous black shales. The goal is to improve our understanding of shale diagenesis by deciphering the origins of these cracks. The cracks are sinuously to ptygmatically folded in a vertical view and weakly sinuous on the bedding plane. They are filled with calcite, bitumen, pyrite, or a combination of them. Evidence of bioturbation and low redox-sensitive trace elemental ratios suggest suboxic to oxic depositional conditions of the shale. The cracks were likely op ened by gas expansion in the unconsolidated mud. The main mineral filling the cracks, calcite, was sourced from hydrothermal fluid that passed through the underlying dolomite. Hydrothermal influences are indicated by the presence of bornite and microcrystalline pyrite in the cracks, as well as Fe and Mn enrichment in the host sediments. Hydrothermal activity can also explain the presence of buddingtonite, an ammonium feldspar in the shale. The results of this study suggest that folded cracks filled by minerals, gradually narrowing towards the top, and lacking internal detrital matrix are likely formed during early diagenesis. The inconsistency between the chemical compositions of the infilling material and the host sediment requires further exploration to identify the source. Hydrothermal fluid passing through the underlying dolomite may be the source of folded calcite cracks in non-calcareous sedimentary rocks. These cracks resemble molar-tooth structures (MTS), which are sinuous cracks filled with micro crystalline calcite mostly found in Precambrian limestone and calcareous shales. If these cracks are indeed MTS, they may be an exception to the age and host-rock lithology constraints of MTS.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135567336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Timur Murtazin, Zufar Kayumov, Vladimir Morozov, Radik Akhmetov, Anton Kolchugin, Dmitrii Tumakov, Danis Nurgaliev, Vladislav Sudakov
The present paper introduces an algorithm for automating the analysis of quartz sandstones and siltstones petrographic thin sections images. The images of thin sections are obtained in polarized light at magnifications providing good image quality. In addition, the images for each section are obtained at different angles of rotation of the microscope stage. Augmentation is applied to the obtained photographs: the number of images increases due to rotations, shifts and rescaling of the image. For training the neural network of the Mask R-CNN architecture, transfer learning is used, with initial weights obtained from a huge variety of non-geological images. The results of image segmentation using Mask R-CNN are compared versus the Watershed algorithm results and the U-Net network for two metrics. According to the standard Intersection over Union metric, U-Net for high quality images and Watershed for blurry images show the best results with a slight superiority. However, according to the Grain Size Metri c, which evaluates the accuracy of grain size measurement, the best accuracy (over 95%) is shown by Mask R-CNN. The grain size analysis is done, and the porosity of the studied petrographic sections is determined. The use of the proposed approaches in the study of thin sections will significantly reduce the time for obtaining the results of grain size distribution analysis and porosity determination.
介绍了一种用于石英砂岩和粉砂岩岩石薄片图像自动分析的算法。薄片的图像是在偏振光下获得的，在放大倍率下提供良好的图像质量。此外，每个切片的图像都是在显微镜台的不同旋转角度下获得的。对获得的照片进行增强:由于图像的旋转，移位和重新缩放，图像数量增加。对于Mask R-CNN架构的神经网络的训练，使用迁移学习，初始权值从大量的非地质图像中获得。使用Mask R-CNN的图像分割结果与分水岭算法结果和U-Net网络进行了两个指标的比较。根据标准的Intersection over Union度量，高质量图像的U-Net和模糊图像的Watershed显示出最佳效果，略有优势。然而，根据评估粒度测量精度的Grain Size Metri c, Mask R-CNN的精度最高(超过95%)。对所研究的岩石剖面进行了粒度分析和孔隙度测定。在薄片研究中使用所提出的方法将大大减少获得粒度分布分析和孔隙率测定结果的时间。
{"title":"High-precision algorithm for grain segmentation of thin section by multi-angle optical-microscopic images","authors":"Timur Murtazin, Zufar Kayumov, Vladimir Morozov, Radik Akhmetov, Anton Kolchugin, Dmitrii Tumakov, Danis Nurgaliev, Vladislav Sudakov","doi":"10.2110/jsr.2022.096","DOIUrl":"https://doi.org/10.2110/jsr.2022.096","url":null,"abstract":"The present paper introduces an algorithm for automating the analysis of quartz sandstones and siltstones petrographic thin sections images. The images of thin sections are obtained in polarized light at magnifications providing good image quality. In addition, the images for each section are obtained at different angles of rotation of the microscope stage. Augmentation is applied to the obtained photographs: the number of images increases due to rotations, shifts and rescaling of the image. For training the neural network of the Mask R-CNN architecture, transfer learning is used, with initial weights obtained from a huge variety of non-geological images. The results of image segmentation using Mask R-CNN are compared versus the Watershed algorithm results and the U-Net network for two metrics. According to the standard Intersection over Union metric, U-Net for high quality images and Watershed for blurry images show the best results with a slight superiority. However, according to the Grain Size Metri c, which evaluates the accuracy of grain size measurement, the best accuracy (over 95%) is shown by Mask R-CNN. The grain size analysis is done, and the porosity of the studied petrographic sections is determined. The use of the proposed approaches in the study of thin sections will significantly reduce the time for obtaining the results of grain size distribution analysis and porosity determination.","PeriodicalId":17044,"journal":{"name":"Journal of Sedimentary Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135567539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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