Pub Date : 2025-05-01Epub Date: 2025-03-06DOI: 10.1016/j.sedgeo.2025.106855
Seung Choi , Shukang Zhang , Noe-Heon Kim , Jin Jung Kweon , Kohei Tanaka , Katsuhiro Kubota , Yuong-Nam Lee , Junfang Xie , In Sung Paik , Sung Keun Lee
Several factors influence the quality of fossil preservation, with temperature being one of the key variables. The maximum temperature that fossils have experienced during their taphonomic history affects their thermal maturity and color. Cretaceous fossil eggs of amniote vertebrates from East Asia were analyzed using Raman spectroscopy to investigate their thermal maturity. Eggs from inland regions of East Asia (Mongolia and inland China) do not show a significant thermal imprint, while eggs from the southern and eastern regions of East Asia (coastal China, Korea, and Japan) show a high thermal maturity. Although this pattern must have been caused by the combined effect of complex factors (e.g., burial depth, stratigraphic position, and local geothermal phenomenon), the rollback of the Paleo-Pacific Plate during the Cretaceous and consequent vigorous igneous activity and/or high heat flow near the subduction boundary may have been one of the main working factors. The approach of this study can be extended to fossil eggs from other continents to elucidate the relationship between thermal maturity and geological setting, and will provide a deeper understanding of fossil egg taphonomy.
{"title":"Thermal maturity and colors of Cretaceous East Asian fossil eggs","authors":"Seung Choi , Shukang Zhang , Noe-Heon Kim , Jin Jung Kweon , Kohei Tanaka , Katsuhiro Kubota , Yuong-Nam Lee , Junfang Xie , In Sung Paik , Sung Keun Lee","doi":"10.1016/j.sedgeo.2025.106855","DOIUrl":"10.1016/j.sedgeo.2025.106855","url":null,"abstract":"<div><div>Several factors influence the quality of fossil preservation, with temperature being one of the key variables. The maximum temperature that fossils have experienced during their taphonomic history affects their thermal maturity and color. Cretaceous fossil eggs of amniote vertebrates from East Asia were analyzed using Raman spectroscopy to investigate their thermal maturity. Eggs from inland regions of East Asia (Mongolia and inland China) do not show a significant thermal imprint, while eggs from the southern and eastern regions of East Asia (coastal China, Korea, and Japan) show a high thermal maturity. Although this pattern must have been caused by the combined effect of complex factors (e.g., burial depth, stratigraphic position, and local geothermal phenomenon), the rollback of the Paleo-Pacific Plate during the Cretaceous and consequent vigorous igneous activity and/or high heat flow near the subduction boundary may have been one of the main working factors. The approach of this study can be extended to fossil eggs from other continents to elucidate the relationship between thermal maturity and geological setting, and will provide a deeper understanding of fossil egg taphonomy.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106855"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143725983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Geological records of the Lower Paleozoic indicate the co-occurrence of large-scale geo- and bio-events, including the diversification of marine complex life and widespread phosphogenesis, making the Early Cambrian aquatic environments a long-standing subject of global interest. Despite extensive research, the interplay between paleoclimate, continental chemical weathering, seawater redox conditions, and salinity during the Cambrian Explosion remains debated. To address this, we conducted geochemical analyses (e.g., XRF, ICP-MS, MRM GC–MS, and IRMS) and optical microscopy on drill cores from the Early Cambrian deep-buried strata (>4 km depth) in an intrashelf basin within the Yangtze Block. Geochemical proxies, including pronounced negative cerium anomalies (as low as 0.20) and a positive pristane-to-phytane ratio excursion, indicate an expansion of oxic waters between ∼531 and 526 Ma, while widespread anoxic conditions prevailed around 531 and 526 Ma. Climate fluctuations between arid and humid periods are inferred from major elements (e.g., Al, Fe, Mn), trace element ratios (e.g., Rb/Sr, Sr/Cu), and rare earth element parameters (e.g., ΣLREE/ΣHREE, Y/Ho). High gammacerane index values (up to 0.41), the presence of β-carotene, elevated Sr/Ba ratio, and δ18O values (up to −4.87 ‰) suggest periods of high salinity and evaporative conditions during arid phases. Organic geochemical signatures, including a high carbon preference index (CPI > 1) and highly negative δ13C values (<−24 ‰), indicate a biological origin of organic matter, with measurable 2-methylhopane (up to 2.48 %) and 4-methylsterane indices (up to 20 %) suggesting contributions from primary producers such as cyanobacteria, alphaproteobacteria, and dinoflagellates. The co-occurrence of oxygenated, highly saline, and evaporative Ca-P-rich waters with the diversification of small shelly fossil assemblages (SSFs 2 and 3) suggests that the studied intrashelf basin provided a favorable setting for the emergence and diversification of complex life. These findings offer new insights into the paleoenvironmental conditions that shaped marine ecosystems during the Cambrian radiation.
{"title":"Integrated investigation of rare earth elements, molecular fossils, and stable isotopes in drill cores from deep-buried strata in the Yangtze Block: Implications for the Early Cambrian sedimentary environments","authors":"Moïse Luemba , Zhonghong Chen , Zhi Chai , Yong Chen , N'nahano-Ruhindwa Heritier , Raphael Matamba","doi":"10.1016/j.sedgeo.2025.106878","DOIUrl":"10.1016/j.sedgeo.2025.106878","url":null,"abstract":"<div><div>Geological records of the Lower Paleozoic indicate the co-occurrence of large-scale geo- and bio-events, including the diversification of marine complex life and widespread phosphogenesis, making the Early Cambrian aquatic environments a long-standing subject of global interest. Despite extensive research, the interplay between paleoclimate, continental chemical weathering, seawater redox conditions, and salinity during the Cambrian Explosion remains debated. To address this, we conducted geochemical analyses (e.g., XRF, ICP-MS, MRM GC–MS, and IRMS) and optical microscopy on drill cores from the Early Cambrian deep-buried strata (>4 km depth) in an intrashelf basin within the Yangtze Block. Geochemical proxies, including pronounced negative cerium anomalies (as low as 0.20) and a positive pristane-to-phytane ratio excursion, indicate an expansion of oxic waters between ∼531 and 526 Ma, while widespread anoxic conditions prevailed around 531 and 526 Ma. Climate fluctuations between arid and humid periods are inferred from major elements (e.g., Al, Fe, Mn), trace element ratios (e.g., Rb/Sr, Sr/Cu), and rare earth element parameters (e.g., ΣLREE/ΣHREE, Y/Ho). High gammacerane index values (up to 0.41), the presence of <em>β</em>-carotene, elevated Sr/Ba ratio, and <em>δ</em><sup><em>18</em></sup><em>O</em> values (up to −4.87 ‰) suggest periods of high salinity and evaporative conditions during arid phases. Organic geochemical signatures, including a high carbon preference index (CPI > 1) and highly negative <em>δ</em><sup><em>13</em></sup><em>C</em> values (<−24 ‰), indicate a biological origin of organic matter, with measurable 2-methylhopane (up to 2.48 %) and 4-methylsterane indices (up to 20 %) suggesting contributions from primary producers such as cyanobacteria, alphaproteobacteria, and dinoflagellates. The co-occurrence of oxygenated, highly saline, and evaporative Ca-P-rich waters with the diversification of small shelly fossil assemblages (SSFs 2 and 3) suggests that the studied intrashelf basin provided a favorable setting for the emergence and diversification of complex life. These findings offer new insights into the paleoenvironmental conditions that shaped marine ecosystems during the Cambrian radiation.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106878"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143768891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-01Epub Date: 2025-03-24DOI: 10.1016/j.sedgeo.2025.106876
William B.F. Ryan , Fadl Raad
A simple box model is developed to access the astronomical-modulated exchange of ocean seawater with the Mediterranean during the Late Miocene salinity crisis. The model differs from previous ones by using a unidirectional portal as the method to get salinity to increase to saturation for gypsum and halite. Flow through the entry portal switches in direction as climate oscillates from arid to wet during each precession cycle. The calculations incorporate a water activity coefficient that reduces the rate of evaporation as salinity increases. As a result, the accumulation rate of gypsum and halite declines with time. The sodium, sulfate, potassium and magnesium ions observed from fluid inclusions in gypsum and halite are replicated in the model. The reduction in input from the exterior ocean and eventual closure of the gateway conforms with the sedimentological and geochemical behavior of the gypsum deposits on margins and halite in salt mines and reflection profiles. By showing that rain and rivers supply eight times more water to the Mediterranean brine than seawater during the hypersaline stage of the Late Miocene salinity crisis, the calculations resolve the geochemical riddle of “low salinity gypsum”. The sulfur isotopes in gypsum derive from ocean seawater and the oxygen and hydrogen isotopes in the gypsum hydration water from atmospheric precipitation.
{"title":"Introducing a water activity coefficient to account for abundance and isotopic compositions of gypsum and halite in the Mediterranean's salt giant deposit","authors":"William B.F. Ryan , Fadl Raad","doi":"10.1016/j.sedgeo.2025.106876","DOIUrl":"10.1016/j.sedgeo.2025.106876","url":null,"abstract":"<div><div>A simple box model is developed to access the astronomical-modulated exchange of ocean seawater with the Mediterranean during the Late Miocene salinity crisis. The model differs from previous ones by using a unidirectional portal as the method to get salinity to increase to saturation for gypsum and halite. Flow through the entry portal switches in direction as climate oscillates from arid to wet during each precession cycle. The calculations incorporate a water activity coefficient that reduces the rate of evaporation as salinity increases. As a result, the accumulation rate of gypsum and halite declines with time. The sodium, sulfate, potassium and magnesium ions observed from fluid inclusions in gypsum and halite are replicated in the model. The reduction in input from the exterior ocean and eventual closure of the gateway conforms with the sedimentological and geochemical behavior of the gypsum deposits on margins and halite in salt mines and reflection profiles. By showing that rain and rivers supply eight times more water to the Mediterranean brine than seawater during the hypersaline stage of the Late Miocene salinity crisis, the calculations resolve the geochemical riddle of “<em>low salinity gypsum</em>”. The sulfur isotopes in gypsum derive from ocean seawater and the oxygen and hydrogen isotopes in the gypsum hydration water from atmospheric precipitation.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106876"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143716249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-01Epub Date: 2025-03-20DOI: 10.1016/j.sedgeo.2025.106874
Soyoung Baek , Kyoung-nam Jo
Surface microtextures of quartz grains (SMQs), which are observable using scanning electron microscopy (SEM), provide direct evidence for reconstructing the sedimentary history of individual grains. Detailed SMQ investigations across diverse modern river systems are essential to better understand the factors controlling SMQ formation in fluvial sediments; however, comprehensive studies of diverse modern fluvial systems remain limited. In this study, we examined SMQ characteristics in a gravel bed of the monsoon-influenced Hantan River on the Korean Peninsula. Hantan River sediments maintain angular to subangular grain outlines throughout downstream areas, exhibiting no gradual changes in either grain outlines or other mechanical microtextures. In contrast to typical fluvial sediment characteristics, upturned plates predominate rather than V-shaped percussion cracks. These features reflect episodic sediment transport driven by seasonal discharge variations in this gravel bed river system. Statistical analysis revealed distinct SMQ frequencies between the mainstream and tributaries, with the mainstream showing higher abrasion features (subangular outlines, conchoidal fractures, and V-shaped percussion cracks), whereas tributaries exhibited fresher surfaces (angular outlines and flat cleavage surfaces). These differences primarily reflect variation in transport distance from source areas, as tributaries, which are shorter and surrounded by mountainous terrain, maintained more direct sediment input characteristics, whereas mainstream sediments showed mixed features due to longer transport distance and tributary inputs. Our SMQ study in modern fluvial environments contributes to enhanced interpretations of past depositional conditions and further suggests a need to refine current SMQ classification systems.
{"title":"Surface microtextures of quartz grains under intermittent sediment transport in a gravel bed in the Hantan River, South Korea","authors":"Soyoung Baek , Kyoung-nam Jo","doi":"10.1016/j.sedgeo.2025.106874","DOIUrl":"10.1016/j.sedgeo.2025.106874","url":null,"abstract":"<div><div>Surface microtextures of quartz grains (SMQs), which are observable using scanning electron microscopy (SEM), provide direct evidence for reconstructing the sedimentary history of individual grains. Detailed SMQ investigations across diverse modern river systems are essential to better understand the factors controlling SMQ formation in fluvial sediments; however, comprehensive studies of diverse modern fluvial systems remain limited. In this study, we examined SMQ characteristics in a gravel bed of the monsoon-influenced Hantan River on the Korean Peninsula. Hantan River sediments maintain angular to subangular grain outlines throughout downstream areas, exhibiting no gradual changes in either grain outlines or other mechanical microtextures. In contrast to typical fluvial sediment characteristics, upturned plates predominate rather than V-shaped percussion cracks. These features reflect episodic sediment transport driven by seasonal discharge variations in this gravel bed river system. Statistical analysis revealed distinct SMQ frequencies between the mainstream and tributaries, with the mainstream showing higher abrasion features (subangular outlines, conchoidal fractures, and V-shaped percussion cracks), whereas tributaries exhibited fresher surfaces (angular outlines and flat cleavage surfaces). These differences primarily reflect variation in transport distance from source areas, as tributaries, which are shorter and surrounded by mountainous terrain, maintained more direct sediment input characteristics, whereas mainstream sediments showed mixed features due to longer transport distance and tributary inputs. Our SMQ study in modern fluvial environments contributes to enhanced interpretations of past depositional conditions and further suggests a need to refine current SMQ classification systems.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106874"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143679209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Trace fossils are widely distributed in pre-extinction Permian successions, and are also relatively common in the Lower Triassic strata. They have been used for evaluating the recovery process of marine infaunal ecosystem following the Permian-Triassic (P-Tr) mass extinction. However, one complicated ichnogenus Balanoglossites has not been clearly recognized and described in the Early Triassic previously, and its importance in revealing biotic recovery in the aftermath of the P-Tr mass extinction has not been evaluated. Here we documented Balanoglossites ichnofabrics from the Lower Triassic Yongningzhen Formation of the Yongningzhen section from Guizhou Province, South China. Balanoglossites is characterized by three-dimensional complex burrow system with Y-shaped and J-shaped galleries and multiple openings, and the herein described form is assigned to B. triadicus. Microstructures of Balanoglossites under SEM and EDS revealed oxidized pyrite framboids occurred merely near the burrow wall, which may be related to activities of the trace maker and symbiotic microorganism such as sulphate-reducing bacteria. Raman spectrum mapping showed that organic matter was enriched along the burrow boundaries of Balanoglossites, but was lacking in the burrow fill. This pattern may result from the impregnation of the burrow walls with organic mucus and bioirrigation by the trace maker. Polychaetes are considered as the most possible trace makers of Balanoglossites, and they were opportunistic pioneers that proliferated in the Early Triassic. The low ichnodiversity of Balanoglossites-bearing strata contrasts with coeval ichnoassemblages, which probably results from intense bioturbation by deeper-tier burrows that prevents the preservation of surficial to shallow-tier trace fossils. Although Balanoglossites is a complex burrow, its occurrence in the Early Triassic is not an indicator of the full recovery of infaunal ecosystem.
{"title":"The Balanoglossites ichnofabrics in the aftermath of the Permian-Triassic mass extinction","authors":"Pengbing Yan , Xueqian Feng , Shiwei Shang , Zhong-Qiang Chen , He Zhao , Ding Zhou , Zijie Zheng , Zemin Zheng","doi":"10.1016/j.sedgeo.2025.106877","DOIUrl":"10.1016/j.sedgeo.2025.106877","url":null,"abstract":"<div><div>Trace fossils are widely distributed in pre-extinction Permian successions, and are also relatively common in the Lower Triassic strata. They have been used for evaluating the recovery process of marine infaunal ecosystem following the Permian-Triassic (P-Tr) mass extinction. However, one complicated ichnogenus <em>Balanoglossites</em> has not been clearly recognized and described in the Early Triassic previously, and its importance in revealing biotic recovery in the aftermath of the P-Tr mass extinction has not been evaluated. Here we documented <em>Balanoglossites</em> ichnofabrics from the Lower Triassic Yongningzhen Formation of the Yongningzhen section from Guizhou Province, South China. <em>Balanoglossites</em> is characterized by three-dimensional complex burrow system with Y-shaped and J-shaped galleries and multiple openings, and the herein described form is assigned to <em>B. triadicus</em>. Microstructures of <em>Balanoglossites</em> under SEM and EDS revealed oxidized pyrite framboids occurred merely near the burrow wall, which may be related to activities of the trace maker and symbiotic microorganism such as sulphate-reducing bacteria. Raman spectrum mapping showed that organic matter was enriched along the burrow boundaries of <em>Balanoglossites</em>, but was lacking in the burrow fill. This pattern may result from the impregnation of the burrow walls with organic mucus and bioirrigation by the trace maker. Polychaetes are considered as the most possible trace makers of <em>Balanoglossites</em>, and they were opportunistic pioneers that proliferated in the Early Triassic. The low ichnodiversity of <em>Balanoglossites</em>-bearing strata contrasts with coeval ichnoassemblages, which probably results from intense bioturbation by deeper-tier burrows that prevents the preservation of surficial to shallow-tier trace fossils. Although <em>Balanoglossites</em> is a complex burrow, its occurrence in the Early Triassic is not an indicator of the full recovery of infaunal ecosystem.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106877"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143785527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-01Epub Date: 2025-03-13DOI: 10.1016/j.sedgeo.2025.106873
Junfeng Zhang , Detian Yan , Dan Zhao , Zeyu Lu
As the oldest shale in South China with potential for exploration, the black shale of the second member of the Doushantuo Formation holds significant research importance and economic value because it records the organic carbon cycle during that period. Previous studies have suggested that the formation of the organic-rich black shale in the second member of the Doushantuo Formation was primarily controlled by an anoxic depositional environment. However, investigations of samples from shelf lagoons have revealed otherwise. In this research, microstructural observations, organic carbon content, elemental geochemistry and Corg-N isotopes of the black shale at the Qinglinkou section and well YD in the middle Yangtze were conducted. The results indicate that the formation mechanisms and paleoenvironment of organic-rich shale in the lower and upper halves of the second member are distinct. The presence of apatite and the characteristics of upwelling proxies suggest the occurrence of upwelling during the sedimentation period of the upper half of the second member. The research results indicate that upwelling directly enhances primary productivity levels during sedimentation in the upper half, bolstering the exchange of nutrients and elements within the water column, which facilitates organic matter enrichment and exacerbates the anoxia of deeper waters. In contrast, the organic matter enrichment in the lower half of the Doushantuo Formation's second member is conventional and is governed primarily by anoxic depositional environments; however, it lacks high productivity and is worse overall than the upper half. Moreover, because the water column is restricted, the organic carbon cycle in the lower half is slow and limited. The organic carbon cycle in the upper half benefits from the nutrients brought by upwelling, which results in better formation and preservation. The role of upwelling in altering the deep-water environment of shelf lagoons and in organic matter accumulation and the organic carbon cycle was emphasized in this study, providing guidance for the study of shale deposition globally during the same period.
{"title":"Upwelling controls organic matter enrichment and organic carbon cycle in the shelf area of the Doushantuo Formation","authors":"Junfeng Zhang , Detian Yan , Dan Zhao , Zeyu Lu","doi":"10.1016/j.sedgeo.2025.106873","DOIUrl":"10.1016/j.sedgeo.2025.106873","url":null,"abstract":"<div><div>As the oldest shale in South China with potential for exploration, the black shale of the second member of the Doushantuo Formation holds significant research importance and economic value because it records the organic carbon cycle during that period. Previous studies have suggested that the formation of the organic-rich black shale in the second member of the Doushantuo Formation was primarily controlled by an anoxic depositional environment. However, investigations of samples from shelf lagoons have revealed otherwise. In this research, microstructural observations, organic carbon content, elemental geochemistry and C<sub>org</sub>-N isotopes of the black shale at the Qinglinkou section and well YD in the middle Yangtze were conducted. The results indicate that the formation mechanisms and paleoenvironment of organic-rich shale in the lower and upper halves of the second member are distinct. The presence of apatite and the characteristics of upwelling proxies suggest the occurrence of upwelling during the sedimentation period of the upper half of the second member. The research results indicate that upwelling directly enhances primary productivity levels during sedimentation in the upper half, bolstering the exchange of nutrients and elements within the water column, which facilitates organic matter enrichment and exacerbates the anoxia of deeper waters. In contrast, the organic matter enrichment in the lower half of the Doushantuo Formation's second member is conventional and is governed primarily by anoxic depositional environments; however, it lacks high productivity and is worse overall than the upper half. Moreover, because the water column is restricted, the organic carbon cycle in the lower half is slow and limited. The organic carbon cycle in the upper half benefits from the nutrients brought by upwelling, which results in better formation and preservation. The role of upwelling in altering the deep-water environment of shelf lagoons and in organic matter accumulation and the organic carbon cycle was emphasized in this study, providing guidance for the study of shale deposition globally during the same period.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"481 ","pages":"Article 106873"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143636551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15Epub Date: 2025-03-01DOI: 10.1016/j.sedgeo.2025.106853
R. Stalder , D. Jaeger , S. Andò , E. Garzanti , C.M. Chiessi , A.O. Sawakuchi , T. Ludwig , M. Strasser
Quartz grains in sediment carried by the Amazon River and five of its major tributaries were analyzed by FTIR-spectroscopy and secondary ion mass spectrometry to evaluate their potential for provenance analysis. Additionally, heavy mineral analysis was performed in the same samples to support sediment discrimination and provenance interpretation. Average defect water contents in quartz grains carried by branches with headwaters draining the Andes are higher (Solimões River 8.8 wt ppm, Madeira River 7.2 wt ppm) than in branches exclusively draining cratonic areas (Xingu River 6.5 wt ppm, Tapajós River 4.6 wt ppm, Negro River 4.7 wt ppm); values in one Amazon mainstem sample are intermediate with prevalence of the Andean signal (7.7 wt ppm). The average defect water content correlates to the fraction of grains that are defect-water rich (> 10 wt ppm), ranging from 30 to 40 % for the Solimões, Madeira, and Amazon Rivers down to 10–20 % for the Tapajós and Negro Rivers. The average molecular-water signal exhibits a much clearer contrast than the OH-defect signal. Grains from cratonic tributaries (Negro, Tapajós and Xingu rivers) exhibit significantly weaker molecular water signals than grains from Andean tributaries (Solimões and Madeira rivers); slightly weaker than the latter is the signal from grains in the Amazon mainstem, reflecting a mixture of Solimões and Negro rivers quartz in the Amazon mainstem sample.
In contrast, trace-element concentrations widely overlap among samples, preventing any robust discrimination about the sources of quartz grains. Trace metals show a fair correlation between Li and Al in all samples; a weak correlation between Al and Ti (indicative of igneous origin) was observed in Negro, Xingu and Amazon River sands, but not in Solimões, Madeira and Tapajós sands. Boron correlates with Li in Tapajós river and Amazon mainstem samples and with Al in Madeira and Tapajós samples.
Heavy-minerals are mostly amphibole, epidote, augitic clinopyroxene and hypersthene in Solimões River sands largely derived from the Andes, and andalusite, amphibole and epidote in Madeira River sands. Cratonic tributaries contribute durable tourmaline and zircon with andalusite (Negro River) or staurolite and topaz (Tapajós River).
The higher content of OH defects and molecular water in quartz grains derived from the Andes than in those from cratonic areas indicates that this property can provide useful complementary information to discriminate the source of quartz grains, one of the thorniest tasks in provenance analysis.
{"title":"Trace element and OH content of quartz grains in the Amazon river: Potential application in provenance analysis","authors":"R. Stalder , D. Jaeger , S. Andò , E. Garzanti , C.M. Chiessi , A.O. Sawakuchi , T. Ludwig , M. Strasser","doi":"10.1016/j.sedgeo.2025.106853","DOIUrl":"10.1016/j.sedgeo.2025.106853","url":null,"abstract":"<div><div>Quartz grains in sediment carried by the Amazon River and five of its major tributaries were analyzed by FTIR-spectroscopy and secondary ion mass spectrometry to evaluate their potential for provenance analysis. Additionally, heavy mineral analysis was performed in the same samples to support sediment discrimination and provenance interpretation. Average defect water contents in quartz grains carried by branches with headwaters draining the Andes are higher (Solimões River 8.8 wt ppm, Madeira River 7.2 wt ppm) than in branches exclusively draining cratonic areas (Xingu River 6.5 wt ppm, Tapajós River 4.6 wt ppm, Negro River 4.7 wt ppm); values in one Amazon mainstem sample are intermediate with prevalence of the Andean signal (7.7 wt ppm). The average defect water content correlates to the fraction of grains that are defect-water rich (> 10 wt ppm), ranging from 30 to 40 % for the Solimões, Madeira, and Amazon Rivers down to 10–20 % for the Tapajós and Negro Rivers. The average molecular-water signal exhibits a much clearer contrast than the OH-defect signal. Grains from cratonic tributaries (Negro, Tapajós and Xingu rivers) exhibit significantly weaker molecular water signals than grains from Andean tributaries (Solimões and Madeira rivers); slightly weaker than the latter is the signal from grains in the Amazon mainstem, reflecting a mixture of Solimões and Negro rivers quartz in the Amazon mainstem sample.</div><div>In contrast, trace-element concentrations widely overlap among samples, preventing any robust discrimination about the sources of quartz grains. Trace metals show a fair correlation between Li and Al in all samples; a weak correlation between Al and Ti (indicative of igneous origin) was observed in Negro, Xingu and Amazon River sands, but not in Solimões, Madeira and Tapajós sands. Boron correlates with Li in Tapajós river and Amazon mainstem samples and with Al in Madeira and Tapajós samples.</div><div>Heavy-minerals are mostly amphibole, epidote, augitic clinopyroxene and hypersthene in Solimões River sands largely derived from the Andes, and andalusite, amphibole and epidote in Madeira River sands. Cratonic tributaries contribute durable tourmaline and zircon with andalusite (Negro River) or staurolite and topaz (Tapajós River).</div><div>The higher content of OH defects and molecular water in quartz grains derived from the Andes than in those from cratonic areas indicates that this property can provide useful complementary information to discriminate the source of quartz grains, one of the thorniest tasks in provenance analysis.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"480 ","pages":"Article 106853"},"PeriodicalIF":2.7,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15Epub Date: 2025-03-02DOI: 10.1016/j.sedgeo.2025.106854
Radha Krishna Pillutla , Andrew Tien-Shun Lin , Jen-Chu Yeh , Gueorgui Ratzov , Nathalie Babonneau , Shu-Kun Hsu , Chih-Chieh Su , Serge Lallemand , Ludvig Löwemark
A giant piston core, MD18–3548 (20.07 m) was collected from a perched basin in the Taiwan accretionary wedge, at a water depth of 1752 m. Detailed grain-size analysis, 14C accelerator mass spectrometry (AMS) dating, and computed tomography (X-CT) scans of the core were performed. Four types of lithofacies, namely hemipelagic sediments, silty turbidite-homogenites, turbidites, and thin silty layers, are identified, along with seventeen event beds. A total of fourteen 14C AMS dating were carried out, with the depositional ages of the event beds being calculated based on the sedimentation rate of hemipelagites. The oldest event bed is ∼12 cal kyrs BP, while the youngest event bed is ∼64 cal yrs BP. All seven homogenite units are floored by a thin (usually <10 cm thick), coarsening-upward first and then fining-upward unit, capped by a thick structureless mud totally devoid of bioturbation. The average thickness of homogenite units is ∼150 cm, while the thickest homogenite unit is ∼200 cm. These homogenite units can be compared to similar deposits reported elsewhere and find particularly that these units exhibit a basal layer with gradual coarsening and fining upward trend in grain size. We therefore propose a new depositional model for the silty turbidite-homogenite units in seismically-shaken enclosed basins. This model takes into account the coarsening-then-fining upward deposition of the basal layers, reported for the first time.
{"title":"Origin and deposition of deepwater homogenites from a sedimentological perspective: Examples from offshore SW Taiwan","authors":"Radha Krishna Pillutla , Andrew Tien-Shun Lin , Jen-Chu Yeh , Gueorgui Ratzov , Nathalie Babonneau , Shu-Kun Hsu , Chih-Chieh Su , Serge Lallemand , Ludvig Löwemark","doi":"10.1016/j.sedgeo.2025.106854","DOIUrl":"10.1016/j.sedgeo.2025.106854","url":null,"abstract":"<div><div>A giant piston core, MD18–3548 (20.07 m) was collected from a perched basin in the Taiwan accretionary wedge, at a water depth of 1752 m. Detailed grain-size analysis, <sup>14</sup>C accelerator mass spectrometry (AMS) dating, and computed tomography (X-CT) scans of the core were performed. Four types of lithofacies, namely hemipelagic sediments, silty turbidite-homogenites, turbidites, and thin silty layers, are identified, along with seventeen event beds. A total of fourteen <sup>14</sup>C AMS dating were carried out, with the depositional ages of the event beds being calculated based on the sedimentation rate of hemipelagites. The oldest event bed is ∼12 cal kyrs BP, while the youngest event bed is ∼64 cal yrs BP. All seven homogenite units are floored by a thin (usually <10 cm thick), coarsening-upward first and then fining-upward unit, capped by a thick structureless mud totally devoid of bioturbation. The average thickness of homogenite units is ∼150 cm, while the thickest homogenite unit is ∼200 cm. These homogenite units can be compared to similar deposits reported elsewhere and find particularly that these units exhibit a basal layer with gradual coarsening and fining upward trend in grain size. We therefore propose a new depositional model for the silty turbidite-homogenite units in seismically-shaken enclosed basins. This model takes into account the coarsening-then-fining upward deposition of the basal layers, reported for the first time.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"480 ","pages":"Article 106854"},"PeriodicalIF":2.7,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-15Epub Date: 2025-02-28DOI: 10.1016/j.sedgeo.2025.106851
Junguang Wang , Zhibao Dong , Zhengcai Zhang , Rongliang Liu , Jiqiao Shi , Ping Lü
Reticulate dunes are the prevalent type of dunes found in deserts worldwide. However, compared to other dune types, systematic research on reticulate dunes remains limited, and aspects such as their formation mechanisms, grain size characteristics, and elemental composition characteristics remain inadequately understood. This study integrated regional wind regime data to analyse the grain size characteristics of reticulate dunes (specifically, the primary and secondary ridges) in the Tengger Desert, Considering both primary and sub-wind seasons. Additionally, we examined the elemental composition characteristics and degree of weathering of these dunes. The results indicate that the primary and secondary ridges of the reticulate dunes in the Tengger Desert are predominantly composed of fine sand and very fine sand with a mean grain size of 2.52Φ. Compared with other deserts in China and abroad, the sediments exhibit relatively finer grain sizes and better sorting. Furthermore, the grain size characteristics of surface sediments in the primary and secondary ridges exhibited two distinct distribution patterns during different wind seasons, indicating differences in the formation mechanisms of the primary and secondary ridges. The major elements in the surface sediments of the reticulate dunes in the Tengger Desert are SiO2 and Al2O3, while the predominant trace elements are primarily Ba, Sr, Zr, and Cr. This indicates that the geochemical composition of the sediments is influenced not only by the intrinsic characteristics of the elements but also by the regional climate and the supply of fresh materials, which are significant factors affecting their chemical behavior and content differences. The chemical weathering indices (CIA, residual coefficient, and ICV), along with the A-CN-K and A-CNK-FM triangular diagrams, suggest that the sedimentary environment of the reticulate dune sediments in the Tengger Desert is characterised by a cold, dry climate with a low degree of weathering. The weathering process occurs during the initial stages of plagioclase chemical weathering. These findings lay the foundation for further research on the formation mechanisms, evolutionary processes, and sedimentary environments of reticulate dunes, contributing to a deeper understanding of these complex geomorphological features.
{"title":"Geochemical composition and grain size of surface sediments from reticulate dunes in the Tengger Desert, China","authors":"Junguang Wang , Zhibao Dong , Zhengcai Zhang , Rongliang Liu , Jiqiao Shi , Ping Lü","doi":"10.1016/j.sedgeo.2025.106851","DOIUrl":"10.1016/j.sedgeo.2025.106851","url":null,"abstract":"<div><div>Reticulate dunes are the prevalent type of dunes found in deserts worldwide. However, compared to other dune types, systematic research on reticulate dunes remains limited, and aspects such as their formation mechanisms, grain size characteristics, and elemental composition characteristics remain inadequately understood. This study integrated regional wind regime data to analyse the grain size characteristics of reticulate dunes (specifically, the primary and secondary ridges) in the Tengger Desert, Considering both primary and sub-wind seasons. Additionally, we examined the elemental composition characteristics and degree of weathering of these dunes. The results indicate that the primary and secondary ridges of the reticulate dunes in the Tengger Desert are predominantly composed of fine sand and very fine sand with a mean grain size of 2.52Φ. Compared with other deserts in China and abroad, the sediments exhibit relatively finer grain sizes and better sorting. Furthermore, the grain size characteristics of surface sediments in the primary and secondary ridges exhibited two distinct distribution patterns during different wind seasons, indicating differences in the formation mechanisms of the primary and secondary ridges. The major elements in the surface sediments of the reticulate dunes in the Tengger Desert are SiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub>, while the predominant trace elements are primarily Ba, Sr, Zr, and Cr. This indicates that the geochemical composition of the sediments is influenced not only by the intrinsic characteristics of the elements but also by the regional climate and the supply of fresh materials, which are significant factors affecting their chemical behavior and content differences. The chemical weathering indices (CIA, residual coefficient, and ICV), along with the A-CN-K and A-CNK-FM triangular diagrams, suggest that the sedimentary environment of the reticulate dune sediments in the Tengger Desert is characterised by a cold, dry climate with a low degree of weathering. The weathering process occurs during the initial stages of plagioclase chemical weathering. These findings lay the foundation for further research on the formation mechanisms, evolutionary processes, and sedimentary environments of reticulate dunes, contributing to a deeper understanding of these complex geomorphological features.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"480 ","pages":"Article 106851"},"PeriodicalIF":2.7,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143551817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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