Pub Date : 2024-11-28DOI: 10.1016/j.sedgeo.2024.106784
Yang Li , Wei Li , Yaohui Xu , Jianyong Xu , Kaiming Su , Hai Liu , Luxing Dou
Terrestrial organic matter (TOM) serves as the primary parent material for source rocks in marine-terrestrial transitional environments. The transport and deposition process of TOM affects the development of high-quality source rocks in shallow marine areas. Based on the sequence stratigraphy of the Enping Formation (upper Eocene to lower Oligocene) in the Baiyun Sag and the petrological characteristics of the source rocks, simulation experiments of terrestrial dispersed organic matter deposition constrained by topography, provenance composition, sedimentation period and other conditions were conducted. Comparative experiments of individual constraints such as topographic slope, hydrodynamic conditions, water salinity and particle size of organic matter were also conducted. The results indicate that TOM enrichment in the littoral delta system initially increases with transport distance but subsequently decreases. Four TOM distribution patterns were identified: interrupted, interbedded, lenticular, and banded types. The interrupted, interbedded, and lenticular types predominantly occur in delta plains, whereas the banded type primarily develops in delta fronts and prodeltas. In the early stages of delta formation, gentle slope conditions are more conducive to the forward transport of TOM. As the delta develops, the sediment thickness increases, which reduces the slope gradient and thus weakens the effect on the transport distance of TOM. Higher flow intensity promotes TOM transport, however, wave action can impede forward transport, creating localized TOM enrichment areas on the delta plain. In shallow water, the increase in water salinity enhances the flocculation of TOM, thus reducing the transport distance of TOM. Meanwhile, Smaller TOM particle sizes correspond to greater transport distances and increased heterogeneity in its planar distribution within the delta-shallow sea sedimentary system.
{"title":"Transport and deposition of terrestrial organic matter in marine littoral deltas: New evidence from flume experiments and 3D laser scanning","authors":"Yang Li , Wei Li , Yaohui Xu , Jianyong Xu , Kaiming Su , Hai Liu , Luxing Dou","doi":"10.1016/j.sedgeo.2024.106784","DOIUrl":"10.1016/j.sedgeo.2024.106784","url":null,"abstract":"<div><div>Terrestrial organic matter (TOM) serves as the primary parent material for source rocks in marine-terrestrial transitional environments. The transport and deposition process of TOM affects the development of high-quality source rocks in shallow marine areas. Based on the sequence stratigraphy of the Enping Formation (upper Eocene to lower Oligocene) in the Baiyun Sag and the petrological characteristics of the source rocks, simulation experiments of terrestrial dispersed organic matter deposition constrained by topography, provenance composition, sedimentation period and other conditions were conducted. Comparative experiments of individual constraints such as topographic slope, hydrodynamic conditions, water salinity and particle size of organic matter were also conducted. The results indicate that TOM enrichment in the littoral delta system initially increases with transport distance but subsequently decreases. Four TOM distribution patterns were identified: interrupted, interbedded, lenticular, and banded types. The interrupted, interbedded, and lenticular types predominantly occur in delta plains, whereas the banded type primarily develops in delta fronts and prodeltas. In the early stages of delta formation, gentle slope conditions are more conducive to the forward transport of TOM. As the delta develops, the sediment thickness increases, which reduces the slope gradient and thus weakens the effect on the transport distance of TOM. Higher flow intensity promotes TOM transport, however, wave action can impede forward transport, creating localized TOM enrichment areas on the delta plain. In shallow water, the increase in water salinity enhances the flocculation of TOM, thus reducing the transport distance of TOM. Meanwhile, Smaller TOM particle sizes correspond to greater transport distances and increased heterogeneity in its planar distribution within the delta-shallow sea sedimentary system.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"475 ","pages":"Article 106784"},"PeriodicalIF":2.7,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142756630","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 : 2024-11-22DOI: 10.1016/j.sedgeo.2024.106782
Chiara Passaseo, Michele Morsilli
Calcareous green algae bioherms have recently gained significant attention in the scientific community, as they serve as valuable stratigraphic and paleoecological archives, comparable to the most studied coral reefs. Currently, the genus Halimeda, which is very abundant in tropical settings and common in temperate ones, contributes significantly to the production of sediments rich in CaCO3. This is due to a rapid calcification process that occurs in its peculiar internal structure. Halimeda bioherms represent a key case because of their non-continuous distribution in the stratigraphic record and in the Modern oceans. In fact, the presence of the green alga Halimeda is widely documented in present-day reefs throughout the entire tropical belt, although extensive bioherms are limited to areas such as the Indonesian K-Bank, the Caribbean, and particularly along the Australian Great Barrier Reef (GBR), where they reach remarkable extensions exceeding 6000 km2. Discontinuous distribution is also noted during the Miocene, with Halimeda bioherms reported only in three main localities within the Mediterranean basin, all dating to the pre-evaporitic Messinian. In this study, we present data obtained from detailed stratigraphic and sedimentological analyses of two small Halimeda bioherms (with a maximum thickness of 5 to 6 m), located in the southernmost portion of the Apulia Carbonate Platform (Salento Peninsula, Italy). Field observations, coupled with thin sections analysis show that despite these two sections being ascribed to different stratigraphic intervals, both record the same facies, with an alternation of shallowing-deepening cycles. While it is documented that different Halimeda species currently inhabiting carbonate systems respond variably to factors such as light, temperature, and salinity, the input of large quantities of nutrients via upwelling currents has recently become the most widely accepted hypothesis to support the occurrence of wide bioherms such as along the GBR. We infer that the occurrence of Salento Messinian Halimeda-rich facies could be related to upwelling of cool, nutrient-rich waters, possibly enhanced by the occurrence of internal waves (IWs). Such processes are well documented in the Salento Peninsula and in many areas of the Mediterranean throughout the Tortonian and likely still acting during the early Messinian.
{"title":"Characterization of Halimeda Bioherms of the Pre-Evaporitic Messinian of the Salento Peninsula (Southern Italy)","authors":"Chiara Passaseo, Michele Morsilli","doi":"10.1016/j.sedgeo.2024.106782","DOIUrl":"10.1016/j.sedgeo.2024.106782","url":null,"abstract":"<div><div>Calcareous green algae bioherms have recently gained significant attention in the scientific community, as they serve as valuable stratigraphic and paleoecological archives, comparable to the most studied coral reefs. Currently, the genus <em>Halimeda</em>, which is very abundant in tropical settings and common in temperate ones, contributes significantly to the production of sediments rich in CaCO<sub>3</sub>. This is due to a rapid calcification process that occurs in its peculiar internal structure. <em>Halimeda</em> bioherms represent a key case because of their non-continuous distribution in the stratigraphic record and in the Modern oceans. In fact, the presence of the green alga <em>Halimeda</em> is widely documented in present-day reefs throughout the entire tropical belt, although extensive bioherms are limited to areas such as the Indonesian K-Bank, the Caribbean, and particularly along the Australian Great Barrier Reef (GBR), where they reach remarkable extensions exceeding 6000 km<sup>2</sup>. Discontinuous distribution is also noted during the Miocene, with <em>Halimeda</em> bioherms reported only in three main localities within the Mediterranean basin, all dating to the pre-evaporitic Messinian. In this study, we present data obtained from detailed stratigraphic and sedimentological analyses of two small <em>Halimeda</em> bioherms (with a maximum thickness of 5 to 6 m), located in the southernmost portion of the Apulia Carbonate Platform (Salento Peninsula, Italy). Field observations, coupled with thin sections analysis show that despite these two sections being ascribed to different stratigraphic intervals, both record the same facies, with an alternation of shallowing-deepening cycles. While it is documented that different <em>Halimeda</em> species currently inhabiting carbonate systems respond variably to factors such as light, temperature, and salinity, the input of large quantities of nutrients via upwelling currents has recently become the most widely accepted hypothesis to support the occurrence of wide bioherms such as along the GBR. We infer that the occurrence of Salento Messinian <em>Halimeda</em>-rich facies could be related to upwelling of cool, nutrient-rich waters, possibly enhanced by the occurrence of internal waves (IWs). Such processes are well documented in the Salento Peninsula and in many areas of the Mediterranean throughout the Tortonian and likely still acting during the early Messinian.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"475 ","pages":"Article 106782"},"PeriodicalIF":2.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142757133","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 : 2024-11-18DOI: 10.1016/j.sedgeo.2024.106781
Jaber Muharrag , Hassan A. Eltom , Ammar El-Husseiny , Fawwaz M. AlKhaldi
Stromatolites, ancient microbial structures, are significant in geological history and important component of carbonate systems. Despite their widespread occurrence, the relationship between stromatolite morphology, stratigraphic context, and petrophysical properties remains underexplored. Based on field observations, and laboratory analysis of 40 samples, this study provides insights into the variation of petrophysical characteristics of stromatolites from the Miocene Dam Formation in eastern Saudi Arabia within different stratigraphic contexts. The results revealed that the stromatolites above and below the sequence boundary (SB) show marked differences in porosity, permeability, and pore system architecture due to varying depositional and diagenetic conditions. Above the SB, stromatolites formed in a transgressive system tract, where fluctuating energy levels influenced sediment types. High-energy conditions in the initial flooding of the transgressive system tract trapped grain-dominated sediments, promoting interparticle and moldic porosity, resulting in higher permeability (up to 1900 mD). In contrast, low-energy conditions after the initial flooding in the transgressive system tract led to the accumulation of mud-dominated sediments, producing microporosity and reducing permeability (as low as 1.8 mD). This variability in rock texture and pore system significantly affects fluid flow dynamics, indicating that stromatolites in these settings could exhibit a wide range of reservoir qualities. Below the SB, stromatolites were deposited in restricted environments that favored lateral growth and the entrapment of mud-supported rock fabrics. Diagenesis modified pore systems of these stromatolites by cementing original porosity while generating vuggy porosity through dissolution, resulting in a more uniform pore structure with narrower permeability ranges compared to those above the SB. The unimodal NMR distribution below the SB, compared to the bimodal distribution above, reflects this more homogeneous pore system, indicating potentially lower but more predictable reservoir quality. This study underscores the importance of stratigraphic context in influencing the petrophysical properties of stromatolites, providing crucial insights for reservoir characterization and predicting fluid flow behavior in carbonate systems.
{"title":"Influence of stromatolites on petrophysical properties within stratigraphic contexts: A case study from the Dam Formation, eastern Saudi Arabia","authors":"Jaber Muharrag , Hassan A. Eltom , Ammar El-Husseiny , Fawwaz M. AlKhaldi","doi":"10.1016/j.sedgeo.2024.106781","DOIUrl":"10.1016/j.sedgeo.2024.106781","url":null,"abstract":"<div><div>Stromatolites, ancient microbial structures, are significant in geological history and important component of carbonate systems. Despite their widespread occurrence, the relationship between stromatolite morphology, stratigraphic context, and petrophysical properties remains underexplored. Based on field observations, and laboratory analysis of 40 samples, this study provides insights into the variation of petrophysical characteristics of stromatolites from the Miocene Dam Formation in eastern Saudi Arabia within different stratigraphic contexts. The results revealed that the stromatolites above and below the sequence boundary (SB) show marked differences in porosity, permeability, and pore system architecture due to varying depositional and diagenetic conditions. Above the SB, stromatolites formed in a transgressive system tract, where fluctuating energy levels influenced sediment types. High-energy conditions in the initial flooding of the transgressive system tract trapped grain-dominated sediments, promoting interparticle and moldic porosity, resulting in higher permeability (up to 1900 mD). In contrast, low-energy conditions after the initial flooding in the transgressive system tract led to the accumulation of mud-dominated sediments, producing microporosity and reducing permeability (as low as 1.8 mD). This variability in rock texture and pore system significantly affects fluid flow dynamics, indicating that stromatolites in these settings could exhibit a wide range of reservoir qualities. Below the SB, stromatolites were deposited in restricted environments that favored lateral growth and the entrapment of mud-supported rock fabrics. Diagenesis modified pore systems of these stromatolites by cementing original porosity while generating vuggy porosity through dissolution, resulting in a more uniform pore structure with narrower permeability ranges compared to those above the SB. The unimodal NMR distribution below the SB, compared to the bimodal distribution above, reflects this more homogeneous pore system, indicating potentially lower but more predictable reservoir quality. This study underscores the importance of stratigraphic context in influencing the petrophysical properties of stromatolites, providing crucial insights for reservoir characterization and predicting fluid flow behavior in carbonate systems.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"475 ","pages":"Article 106781"},"PeriodicalIF":2.7,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142757132","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 : 2024-11-14DOI: 10.1016/j.sedgeo.2024.106771
Tomasz Salamon
Eskers are one of the meltwater landforms that enable the reconstruction of the nature of subglacial drainage systems. Therefore, they play a significant role in the study of palaeo ice sheets. While the spatial distribution of subglacial tunnels and their geometry resulting from the geomorphological features of eskers are relatively well known, the course and time of sedimentation processes taking place inside the subglacial conduits are understood only to a certain extent, especially in the case of eskers developed on soft substrata. The paper presents an example of an esker that developed on a soft substratum from Central-North Poland, which was formed in several stages. In the initial stage, meltwater drainage took place through a channel that dissected the substratum (N-channel). Its development was associated with intense flow under pressure, but the sediments filling the channel were already deposited under atmospheric pressure when the flow used only part of the available space of the conduit. The high frequency of large-scale, cross-stratified lithofacies indicates significant flow depth and sediment deposition under a lower flow regime. The succession filling the channel resembles the sediments of a low-sinuosity open river systems with varied channel morphology, however, it also contains deposits like the point bar succession. Later, the R-channel developed, dominated by deposition from supercritical flows, probably of a much smaller depth. The sediments were deposited from a traction carpet or a highly turbulent suspension. The massive structure of many lithofacies indicates that flow overload was common. The transformation of the system from N-channel to R-channel was probably related to the decrease in the slope of the ice sheet surface during ablation, which resulted in a reduction of the potential hydraulic pressure gradient. The final stage of esker sedimentation was associated with deposition in an open channel, which indicates the passive nature of the marginal part of the ice sheet.
冰盖是一种融水地貌，可以重建冰川下排水系统的性质。因此，它们在古冰川研究中发挥着重要作用。虽然人们对冰川下隧道的空间分布及其因冰川裂谷的地貌特征而形成的几何形状比较了解，但对冰川下通道内沉积过程的过程和时间只有一定程度的了解，特别是对发育在软基质上的冰川裂谷。本文举例说明了波兰中北部软基质上形成的冰盖，该冰盖的形成分为几个阶段。在最初阶段，融水通过一条切割基底的通道（N-通道）排出。该通道的形成与压力下的剧烈流动有关，但当水流仅使用通道的部分可用空间时，填充通道的沉积物已经在大气压力下沉积。大尺度、交叉层理岩性的高频率出现表明，水流深度较大，沉积物沉积在较低的水流状态下。填充河道的演替类似于河道形态多变的低稀度开阔河系的沉积物，但也包含类似于点条形演替的沉积物。后来，R 型河道形成，主要是超临界水流的沉积，水深可能要小得多。沉积物由牵引地毯或高度湍动的悬浮物沉积而成。许多岩层的块状结构表明，水流超载现象十分普遍。该系统从 N 沟道到 R 沟道的转变可能与消融过程中冰原表面坡度的减小有关，这导致了潜在水压梯度的减小。沼泽沉积的最后阶段与明渠沉积有关，这表明冰原边缘部分的被动性质。
{"title":"The sedimentology and multi-stage evolution of a Pleistocene esker on soft substratum, a case from North Central Poland","authors":"Tomasz Salamon","doi":"10.1016/j.sedgeo.2024.106771","DOIUrl":"10.1016/j.sedgeo.2024.106771","url":null,"abstract":"<div><div>Eskers are one of the meltwater landforms that enable the reconstruction of the nature of subglacial drainage systems. Therefore, they play a significant role in the study of palaeo ice sheets. While the spatial distribution of subglacial tunnels and their geometry resulting from the geomorphological features of eskers are relatively well known, the course and time of sedimentation processes taking place inside the subglacial conduits are understood only to a certain extent, especially in the case of eskers developed on soft substrata. The paper presents an example of an esker that developed on a soft substratum from Central-North Poland, which was formed in several stages. In the initial stage, meltwater drainage took place through a channel that dissected the substratum (N-channel). Its development was associated with intense flow under pressure, but the sediments filling the channel were already deposited under atmospheric pressure when the flow used only part of the available space of the conduit. The high frequency of large-scale, cross-stratified lithofacies indicates significant flow depth and sediment deposition under a lower flow regime. The succession filling the channel resembles the sediments of a low-sinuosity open river systems with varied channel morphology, however, it also contains deposits like the point bar succession. Later, the R-channel developed, dominated by deposition from supercritical flows, probably of a much smaller depth. The sediments were deposited from a traction carpet or a highly turbulent suspension. The massive structure of many lithofacies indicates that flow overload was common. The transformation of the system from N-channel to R-channel was probably related to the decrease in the slope of the ice sheet surface during ablation, which resulted in a reduction of the potential hydraulic pressure gradient. The final stage of esker sedimentation was associated with deposition in an open channel, which indicates the passive nature of the marginal part of the ice sheet.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"474 ","pages":"Article 106771"},"PeriodicalIF":2.7,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142705948","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 : 2024-11-14DOI: 10.1016/j.sedgeo.2024.106772
Xiaolan Jia , Mohammad Alsuwaidi , Daniel Morad , Juan Diego Martín-Martín , Xia Wang , Kate Al Tameemi , Bashayer Al Muhairi
This petrographic, petrophysical, and geochemical study revealed that dolomitization in the Upper Jurassic Arab Formation reservoir, United Arab Emirates, can be constrained within 2nd, 3rd, and 4th order sequences. The formation represents a 2nd order regressive sequence/cycle (highstand systems tracts, HST) that was deposited across a carbonate ramp with shoal under hot arid climatic conditions during the Kimmeridgian-Tithonian. Deposition occurred subsequent to maximum marine transgression (maximum flooding surface, MFS) and was accompanied by a progressive increase in the degree of restriction of the connectivity between the inner platform (supratidal, upper intertidal and lagoon) and the open sea. Sporadic dolomitization took place in transgressive systems tracts (TST) of the 3rd and 4th order cycles of earliest stages of the 2nd order regression, below the parasequence boundaries and within bioturbation sites. Subsequent rapid and extended 2nd order marine regression cycles were embossed by trends of progressive increase in salinity, which resulted in concomitant systematic decrease in limestone deposition and increase in intensity of seepage reflux/sabkha dolomitization by seepage reflux of hypersaline brines. Dolomitization is most prevalent in the 4th order HST sequences and was accompanied by occlusion of the moldic and intercrystalline pores in the dolostones by gypsum/anhydrite cement. Dolomitization that was accompanied by limited formation of gypsum/anhydrite in the late 2nd order HST is attributed to reflux of penesaline (salinity saturated with Ca-sulfate) /mesohaline (below Ca-sulfate saturation) brines. The reflux of the latter brines is attributed to smaller extent of relative sea-level falls, i.e., partial restriction of the inner platform. The precipitation of dolomite cement in moldic pores and as thin overgrowths around replacive dolomite is attributed to the flow hot basinal brines (i.e., hydrothermal fluids). This interpretation is supported by the presence of saddle dolomite, along with depleted δ18O values, relative enrichment in 87Sr isotope, and high fluid-inclusions homogenization temperatures. The greater amounts of these post-dolomitization cements in the dolopackstones and dolograinstones caused stronger obliteration of their near-surface isotopic signatures compared to the dolomudstones and dolowackestones.
This study demonstrates that linking dolomitization of limestones across carbonate ramps under hot-arid climatic conditions to different orders of changes in the relative sea level and lithology of the succession indicates the involvement of various types of dolomitizing fluids and geochemical conditions, including: (i) domination of seepage reflux of hypersaline and mesohaline/penesaline brines, (ii) dolomitization below the seafloor during marine transgression, and (iii) dolomitization within bioturbation sites.
{"title":"Linking dolomitization to sequence stratigraphy: Insights from the Upper Jurassic Arab Formation, offshore oilfield, UAE","authors":"Xiaolan Jia , Mohammad Alsuwaidi , Daniel Morad , Juan Diego Martín-Martín , Xia Wang , Kate Al Tameemi , Bashayer Al Muhairi","doi":"10.1016/j.sedgeo.2024.106772","DOIUrl":"10.1016/j.sedgeo.2024.106772","url":null,"abstract":"<div><div>This petrographic, petrophysical, and geochemical study revealed that dolomitization in the Upper Jurassic Arab Formation reservoir, United Arab Emirates, can be constrained within 2nd, 3rd, and 4th order sequences. The formation represents a 2nd order regressive sequence/cycle (highstand systems tracts, HST) that was deposited across a carbonate ramp with shoal under hot arid climatic conditions during the Kimmeridgian-Tithonian. Deposition occurred subsequent to maximum marine transgression (maximum flooding surface, MFS) and was accompanied by a progressive increase in the degree of restriction of the connectivity between the inner platform (supratidal, upper intertidal and lagoon) and the open sea. Sporadic dolomitization took place in transgressive systems tracts (TST) of the 3rd and 4th order cycles of earliest stages of the 2nd order regression, below the parasequence boundaries and within bioturbation sites. Subsequent rapid and extended 2nd order marine regression cycles were embossed by trends of progressive increase in salinity, which resulted in concomitant systematic decrease in limestone deposition and increase in intensity of seepage reflux/sabkha dolomitization by seepage reflux of hypersaline brines. Dolomitization is most prevalent in the 4th order HST sequences and was accompanied by occlusion of the moldic and intercrystalline pores in the dolostones by gypsum/anhydrite cement. Dolomitization that was accompanied by limited formation of gypsum/anhydrite in the late 2nd order HST is attributed to reflux of penesaline (salinity saturated with Ca-sulfate) /mesohaline (below Ca-sulfate saturation) brines. The reflux of the latter brines is attributed to smaller extent of relative sea-level falls, i.e., partial restriction of the inner platform. The precipitation of dolomite cement in moldic pores and as thin overgrowths around replacive dolomite is attributed to the flow hot basinal brines (i.e., hydrothermal fluids). This interpretation is supported by the presence of saddle dolomite, along with depleted δ<sup>18</sup>O values, relative enrichment in <sup>87</sup>Sr isotope, and high fluid-inclusions homogenization temperatures. The greater amounts of these post-dolomitization cements in the dolopackstones and dolograinstones caused stronger obliteration of their near-surface isotopic signatures compared to the dolomudstones and dolowackestones.</div><div>This study demonstrates that linking dolomitization of limestones across carbonate ramps under hot-arid climatic conditions to different orders of changes in the relative sea level and lithology of the succession indicates the involvement of various types of dolomitizing fluids and geochemical conditions, including: (i) domination of seepage reflux of hypersaline and mesohaline/penesaline brines, (ii) dolomitization below the seafloor during marine transgression, and (iii) dolomitization within bioturbation sites.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"474 ","pages":"Article 106772"},"PeriodicalIF":2.7,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142705946","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 : 2024-11-06DOI: 10.1016/j.sedgeo.2024.106770
Zilong Wang, Shaobin Guo
Clear geochronology and precise interpretation of sequence stratigraphy enhance our understanding of continental lake-level evolution. The Songliao Basin features well-preserved Cretaceous continental strata. Nevertheless, the correlation between lake-level fluctuations and global sea-level changes remains ambiguous. High-resolution gamma ray logging data were used to analyze the cyclical stratigraphy of the lower member of the Early Cretaceous Shahezi Formation in the Songliao Basin. X-ray fluorescence experiments characterized the sedimentary environment of this formation. Lake-level variations in the lower part of the Early Cretaceous Shahezi Formation were reconstructed using sedimentary noise modeling based on finely tuned gamma ray logging data. Time series analysis using the tuned gamma ray data established an astronomical timescale of approximately 2.4 Myr within the lower section of the early Cretaceous Shahezi Formation in the Songliao Basin. A volcanic ash layer dating (118.20 ± 1.5) Ma from the base of the Shahezi Formation served as an anchor point, providing an absolute astronomical timescale ranging from 115.80 to 118.20 Ma for the study region. The sedimentary model indicates that variations in paleowater depth within the lower section of the Shahezi Formation closely match fluctuations observed in the Fe/Mn index, which reflects paleowater depth changes. This introduces a novel approach to assess changes in continental lake levels. The sedimentary noise model revealed a notable obliquity cycle of about 1.2 million years, strongly associated with fluctuations in lake levels. This indicates that prolonged obliquity periods affect lake level variations. Intriguingly, when lake levels rise, global sea levels concurrently decline, highlighting an inverse relationship between these phenomena. This observation offers insights into how long-term obliquity-driven climate changes regulate sea and lake levels.
{"title":"Analysis of lake level fluctuations in the Early Cretaceous Songliao Basin supports aquifer eustacy","authors":"Zilong Wang, Shaobin Guo","doi":"10.1016/j.sedgeo.2024.106770","DOIUrl":"10.1016/j.sedgeo.2024.106770","url":null,"abstract":"<div><div>Clear geochronology and precise interpretation of sequence stratigraphy enhance our understanding of continental lake-level evolution. The Songliao Basin features well-preserved Cretaceous continental strata. Nevertheless, the correlation between lake-level fluctuations and global sea-level changes remains ambiguous. High-resolution gamma ray logging data were used to analyze the cyclical stratigraphy of the lower member of the Early Cretaceous Shahezi Formation in the Songliao Basin. X-ray fluorescence experiments characterized the sedimentary environment of this formation. Lake-level variations in the lower part of the Early Cretaceous Shahezi Formation were reconstructed using sedimentary noise modeling based on finely tuned gamma ray logging data. Time series analysis using the tuned gamma ray data established an astronomical timescale of approximately 2.4 Myr within the lower section of the early Cretaceous Shahezi Formation in the Songliao Basin. A volcanic ash layer dating (118.20 ± 1.5) Ma from the base of the Shahezi Formation served as an anchor point, providing an absolute astronomical timescale ranging from 115.80 to 118.20 Ma for the study region. The sedimentary model indicates that variations in paleowater depth within the lower section of the Shahezi Formation closely match fluctuations observed in the Fe/Mn index, which reflects paleowater depth changes. This introduces a novel approach to assess changes in continental lake levels. The sedimentary noise model revealed a notable obliquity cycle of about 1.2 million years, strongly associated with fluctuations in lake levels. This indicates that prolonged obliquity periods affect lake level variations. Intriguingly, when lake levels rise, global sea levels concurrently decline, highlighting an inverse relationship between these phenomena. This observation offers insights into how long-term obliquity-driven climate changes regulate sea and lake levels.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"474 ","pages":"Article 106770"},"PeriodicalIF":2.7,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655372","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 : 2024-11-06DOI: 10.1016/j.sedgeo.2024.106769
Khalil Azennoud , Yassine Ait Brahim , Abdennasser Baali , Franziska A. Lechleitner , Hicham El Asmi , Xianglei Li , R. Lawrence Edwards , Matthew Peros
The Quaternary Period climatic oscillations, typically those driven by Milankovitch cycles, have significantly left profound imprints in the geological records. However, the potential of terrestrial archives, particularly tufa deposits, as archives for Quaternary climate remain relatively underexplored. This study aims to contribute to filling the gap in a data-scarce region (Northwest Africa) through investigating Middle Pleistocene to Holocene groundwater-fed tufa deposits, using fieldwork-based, process-oriented facies analysis and advanced 230Th technique. Eight stratigraphic sections were measured, identifying thirteen sedimentary facies grouped into four facies associations representing specific depositional settings: (i) fluvio-lacustrine and palustrine tufa, (ii) barrage cascade tufa with buttresses, (iii) tufa in channels with pools, and (iv) tufa in shallow braided channels with free-flowing water. The depositional system comprises a single multi-story wedge of vertically and laterally stacked barrage-cascade dammed-area systems.
Our Integrated analysis revealed significant tufa growth during MIS 14, with implications for a warm and humid MISs 15–13 ‘extra-long interglacial’, consistent with multiple paleoclimate records. Such conditions would have supported late Acheulean hominin occupation and the emergence of Early Modern Humans in the region around 300 ka. The findings also highlight the possible impact of the Mid-Brunhes Event (MBE) on tufa deposition patterns, likely through CO2-climate feedbacks, underscoring the sensitivity of tufa records to global climatic changes. Moreover, the study outcomes suggest significant regional tectonic activity during the late Middle Pleistocene, causing counter-clockwise rotation and northward tilting of MIS 14 deposits. The associated seismic events may have modified the hydrogeological budget and, by extension, altered the balance between tufa aggradation and degradation. The rotation about the vertical axis suggests a bookshelf faulting mechanism driven by regional left-lateral strike-slip tectonics. Differential karstic dissolution and tectonic forces would have further contributed to deposit tilting. The study highlights the potential of tufa as a valuable terrestrial archive for understanding Quaternary climate dynamics and tectonic processes. Future research should aim to expand the chronological framework and further investigate the climatic and tectonic influences on tufa deposition in this data-scarce region. This can be achieved through additional 230Th dating, high-resolution stable isotope measurements on microbialites, particularly focusing on the significance of the Mid-Brunhes Event (MBE) in Northwest Africa.
第四纪气候振荡，通常是由米兰科维奇周期驱动的气候振荡，在地质记录中留下了深刻的烙印。然而，陆地档案（尤其是土法沉积）作为第四纪气候档案的潜力仍未得到充分发掘。本研究旨在通过调查中更新世至全新世地下水滋养的土法沉积，采用基于野外工作、过程导向的岩相分析和先进的 230Th 技术，填补数据稀缺地区（西北非）的这一空白。对八个地层剖面进行了测量，确定了 13 个沉积面，分为代表特定沉积环境的四个面系：(i) 河积-湖积和湖积土陶，(ii) 带支墩的拦河坝级联土陶，(iii) 有水池的渠道中的土陶，(iv) 有自由水流的浅辫状渠道中的土陶。我们的综合分析表明，在MIS 14期间，有大量的泥灰华生长，这意味着MIS 15-13期间有一个温暖湿润的 "超长冰期"，这与多种古气候记录相一致。这样的条件将支持阿切莱恩晚期类人猿占领该地区，并在 300 ka 左右出现早期现代人。研究结果还强调了布伦瑞斯中期事件（MBE）可能通过二氧化碳-气候反馈作用对图瓦沉积模式产生的影响，突出了图瓦记录对全球气候变化的敏感性。此外，研究结果表明，中更新世晚期发生了重大的区域构造活动，导致 MIS 14 沉积物逆时针旋转并向北倾斜。相关的地震事件可能改变了水文地质预算，并进而改变了泥灰岩增生和退化之间的平衡。围绕纵轴的旋转表明，区域性左侧走向滑动构造驱动了书架式断层机制。岩溶溶解和构造力的差异会进一步加剧沉积物的倾斜。这项研究强调了泥灰岩作为了解第四纪气候动态和构造过程的宝贵陆地档案的潜力。未来的研究应旨在扩展年代学框架，并进一步研究气候和构造对这一数据稀缺地区的岩土沉积的影响。这可以通过对微生物岩进行更多的 230Th 测定、高分辨率稳定同位素测量来实现，尤其要关注西北非洲中布鲁内斯事件（MBE）的重要性。
{"title":"Tufas record significant imprints of climate and tectonic activity over the past 600 ka: Evidence from a multi-story wedge in Northwest Africa","authors":"Khalil Azennoud , Yassine Ait Brahim , Abdennasser Baali , Franziska A. Lechleitner , Hicham El Asmi , Xianglei Li , R. Lawrence Edwards , Matthew Peros","doi":"10.1016/j.sedgeo.2024.106769","DOIUrl":"10.1016/j.sedgeo.2024.106769","url":null,"abstract":"<div><div>The Quaternary Period climatic oscillations, typically those driven by Milankovitch cycles, have significantly left profound imprints in the geological records. However, the potential of terrestrial archives, particularly tufa deposits, as archives for Quaternary climate remain relatively underexplored. This study aims to contribute to filling the gap in a data-scarce region (Northwest Africa) through investigating Middle Pleistocene to Holocene groundwater-fed tufa deposits, using fieldwork-based, process-oriented facies analysis and advanced <sup>230</sup>Th technique. Eight stratigraphic sections were measured, identifying thirteen sedimentary facies grouped into four facies associations representing specific depositional settings: (i) fluvio-lacustrine and palustrine tufa, (ii) barrage cascade tufa with buttresses, (iii) tufa in channels with pools, and (iv) tufa in shallow braided channels with free-flowing water. The depositional system comprises a single multi-story wedge of vertically and laterally stacked barrage-cascade dammed-area systems.</div><div>Our Integrated analysis revealed significant tufa growth during MIS 14, with implications for a warm and humid MISs 15–13 ‘extra-long interglacial’, consistent with multiple paleoclimate records. Such conditions would have supported late Acheulean hominin occupation and the emergence of Early Modern Humans in the region around 300 ka. The findings also highlight the possible impact of the Mid-Brunhes Event (MBE) on tufa deposition patterns, likely through CO<sub>2</sub>-climate feedbacks, underscoring the sensitivity of tufa records to global climatic changes. Moreover, the study outcomes suggest significant regional tectonic activity during the late Middle Pleistocene, causing counter-clockwise rotation and northward tilting of MIS 14 deposits. The associated seismic events may have modified the hydrogeological budget and, by extension, altered the balance between tufa aggradation and degradation. The rotation about the vertical axis suggests a bookshelf faulting mechanism driven by regional left-lateral strike-slip tectonics. Differential karstic dissolution and tectonic forces would have further contributed to deposit tilting. The study highlights the potential of tufa as a valuable terrestrial archive for understanding Quaternary climate dynamics and tectonic processes. Future research should aim to expand the chronological framework and further investigate the climatic and tectonic influences on tufa deposition in this data-scarce region. This can be achieved through additional <sup>230</sup>Th dating, high-resolution stable isotope measurements on microbialites, particularly focusing on the significance of the Mid-Brunhes Event (MBE) in Northwest Africa.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"474 ","pages":"Article 106769"},"PeriodicalIF":2.7,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142705947","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 : 2024-11-01DOI: 10.1016/j.sedgeo.2024.106768
Liang Yue, Yangquan Jiao, Liqun Wu, Hui Rong
Negative δ34S values of sedimentary pyrite associated with organic matter are routinely assumed to be the result of biogenic process. However, the distribution and evolution of isotopic values mediated by bacteria across sedimentary strata remains poorly understood. Abundant pyrite-rich nodules (PyRNs) are distributed in the bottom of the sandstone unconformably overlying the coal in middle Jurassic strata in the northeastern Ordos Basin, providing a good opportunity to quantitatively characterize the distribution, morphology and compositions of sulfur isotope and trace element of pyrite in the sandstone influenced by organic matter in the coal. A total of 1007 PyRNs occurs within a range of 4 m from the coal. From bottom to top in the sandstone, the shape of the nodule changes from oval to round on the vertical section, and the length and number gradually decrease at the rate of ~45 mm and ~ 228 for every 1 m increase in distance, respectively. Microscopically, pyrite occurs as euhedral crystals, and trace element mapping reveals multistage growth (up to a dozen times) and a marked compositional zoning with respect to Co, Ni, As, Se and Mo. The positive correlation between Co and Ni, with ratios of Co/Ni ranging from 0.06 to 0.45, indicates that Fe and those trace elements are sourced from diagenetic fluid. The organic sulfur in coal, serving as a sulfur source, is reduced by bacteria to generate H232S at a slow reduction rate. The H232S migrates upwards and reacts with Fe to form pyrite in the sandstone, resulting in extremely low δ34S values (from −53.9 to −43.1 ‰), which gradual decrease both from core to margin in individual grain and at the rate of 2.2 to 8.8 ‰ for every 1 m increase in distance away from the coal. This study highlights the significant variability of mineralogical (e.g., number, size, morphology) and geochemical (trace elements, sulfur isotope) characteristics of sedimentary pyrite. Results allow the relation of multistage growth of pyrite to biogenic fractionation, and provide fresh insights into biogenically derived sulfur from coals to be fixed in sandstones, which can be applied to quantitative characterization of formation processes of sedimentary minerals controlled by organic matter in sedimentary environments worldwide.
{"title":"Quantitative characterization on multistage formation of sedimentary pyrite driven by H2S derived from biogenic process in the northeastern Ordos Basin, China","authors":"Liang Yue, Yangquan Jiao, Liqun Wu, Hui Rong","doi":"10.1016/j.sedgeo.2024.106768","DOIUrl":"10.1016/j.sedgeo.2024.106768","url":null,"abstract":"<div><div>Negative δ<sup>34</sup>S values of sedimentary pyrite associated with organic matter are routinely assumed to be the result of biogenic process. However, the distribution and evolution of isotopic values mediated by bacteria across sedimentary strata remains poorly understood. Abundant pyrite-rich nodules (PyRNs) are distributed in the bottom of the sandstone unconformably overlying the coal in middle Jurassic strata in the northeastern Ordos Basin, providing a good opportunity to quantitatively characterize the distribution, morphology and compositions of sulfur isotope and trace element of pyrite in the sandstone influenced by organic matter in the coal. A total of 1007 PyRNs occurs within a range of 4 m from the coal. From bottom to top in the sandstone, the shape of the nodule changes from oval to round on the vertical section, and the length and number gradually decrease at the rate of ~45 mm and ~ 228 for every 1 m increase in distance, respectively. Microscopically, pyrite occurs as euhedral crystals, and trace element mapping reveals multistage growth (up to a dozen times) and a marked compositional zoning with respect to Co, Ni, As, Se and Mo. The positive correlation between Co and Ni, with ratios of Co/Ni ranging from 0.06 to 0.45, indicates that Fe and those trace elements are sourced from diagenetic fluid. The organic sulfur in coal, serving as a sulfur source, is reduced by bacteria to generate H<sub>2</sub><sup>32</sup>S at a slow reduction rate. The H<sub>2</sub><sup>32</sup>S migrates upwards and reacts with Fe to form pyrite in the sandstone, resulting in extremely low δ<sup>34</sup>S values (from −53.9 to −43.1 ‰), which gradual decrease both from core to margin in individual grain and at the rate of 2.2 to 8.8 ‰ for every 1 m increase in distance away from the coal. This study highlights the significant variability of mineralogical (e.g., number, size, morphology) and geochemical (trace elements, sulfur isotope) characteristics of sedimentary pyrite. Results allow the relation of multistage growth of pyrite to biogenic fractionation, and provide fresh insights into biogenically derived sulfur from coals to be fixed in sandstones, which can be applied to quantitative characterization of formation processes of sedimentary minerals controlled by organic matter in sedimentary environments worldwide.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"473 ","pages":"Article 106768"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658920","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}
<div><div>This study examined the waters and carbonates from two cold spring travertines (ca. 13 °C) located on the sun-exposed (north-facing travertine) and sun-shaded (south-facing travertine) margins of Laguna Amarga, an alkaline lake from the semiarid region of the eastern Patagonian Andes (51°S).</div><div>The travertines are composed of calcite + low-Mg calcite ± aragonite. Both exhibit similar sedimentological transitions along their longitudinal profiles. In the proximal zones, biologically-influenced carbonates form in wetland-like environments. Spherulitic calcite precipitates in association with extracellular polymeric substances in microbial biofilms containing cyanobacteria-like molds at the vent of the south-facing travertine, while aragonite spherulite formation at the north-facing travertine vent also involves sulfate-reducing bacteria, as indicated by their close association with framboidal pyrite. Downstream, in the intermediate and distal zones, crystalline dendrites predominantly precipitate due to increased turbulence-induced CO<sub>2</sub> degassing.</div><div>Both travertines share a similar range of carbonate <sup>87</sup>Sr/<sup>86</sup>Sr composition (0.70720–0.70740) and isotopic signatures of the spring waters, including δ<sup>2</sup>H (ca. −110 ‰ VSMOW), δ<sup>18</sup>O<sub>water</sub> (ca. −14 ‰ VSMOW) and δ<sup>13</sup>C-DIC (ca. −5 ‰ VPDB), suggesting common sources and processes influencing fluid composition. This points to the dissolution of carbonates from mudstone-rich marine units of the Lower Cretaceous (δ<sup>13</sup>C ca. −1 ‰ VPDB) and Upper Cretaceous (δ<sup>13</sup>C ca. −10 ‰ VPDB) during shallow subsurface circulation of meteoric waters through the bedrock. The carbon isotopic composition of the deposits resembles those of endogenic travertines (δ<sup>13</sup>C<sub>trav</sub> −1.2 to 5.3 ‰ VPDB), with the highest δ<sup>13</sup>C<sub>trav</sub> values associated with carbonates from the vents. However, the involvement of deep CO<sub>2</sub> sources is unclear and epigenic processes capable of producing the observed <sup>13</sup>C enrichments are discussed.</div><div>Despite their common sources, similar sedimentological features and δ<sup>18</sup>O<sub>trav</sub> compositional range (−12.4 to −10.1 ‰ VPDB), the δ<sup>13</sup>C<sub>trav</sub> values are lower in the south-facing travertine (−1.2 to 1.9 ‰ VPDB) compared to the north-facing travertine (1.8 to 5.3 ‰ VPDB). This disparity is inferred to result from variations in local environmental conditions due to different levels of insolation, which favored the incorporation of soil-derived CO<sub>2</sub> in the south-facing travertine and likely increased photosynthetic productivity in the north-facing travertine, thereby shifting their δ<sup>13</sup>C<sub>trav</sub> signatures to lower and higher values, respectively. These relationships highlight the sensitivity of low-temperature spring carbonates to subtle environmental changes at basin scales.</div
{"title":"Similar sources but distinct δ13C signatures in adjacent low-temperature travertines from Laguna Amarga (Southern Patagonian Andes)","authors":"Paulo Quezada , Leonardo Fadel Cury , Mauricio Calderón , Carolina Henríquez , Luis Mancini , Joicy Micheletto , Gustavo Barbosa Athayde , Anelize Bahniuk Rumbelsperger","doi":"10.1016/j.sedgeo.2024.106758","DOIUrl":"10.1016/j.sedgeo.2024.106758","url":null,"abstract":"<div><div>This study examined the waters and carbonates from two cold spring travertines (ca. 13 °C) located on the sun-exposed (north-facing travertine) and sun-shaded (south-facing travertine) margins of Laguna Amarga, an alkaline lake from the semiarid region of the eastern Patagonian Andes (51°S).</div><div>The travertines are composed of calcite + low-Mg calcite ± aragonite. Both exhibit similar sedimentological transitions along their longitudinal profiles. In the proximal zones, biologically-influenced carbonates form in wetland-like environments. Spherulitic calcite precipitates in association with extracellular polymeric substances in microbial biofilms containing cyanobacteria-like molds at the vent of the south-facing travertine, while aragonite spherulite formation at the north-facing travertine vent also involves sulfate-reducing bacteria, as indicated by their close association with framboidal pyrite. Downstream, in the intermediate and distal zones, crystalline dendrites predominantly precipitate due to increased turbulence-induced CO<sub>2</sub> degassing.</div><div>Both travertines share a similar range of carbonate <sup>87</sup>Sr/<sup>86</sup>Sr composition (0.70720–0.70740) and isotopic signatures of the spring waters, including δ<sup>2</sup>H (ca. −110 ‰ VSMOW), δ<sup>18</sup>O<sub>water</sub> (ca. −14 ‰ VSMOW) and δ<sup>13</sup>C-DIC (ca. −5 ‰ VPDB), suggesting common sources and processes influencing fluid composition. This points to the dissolution of carbonates from mudstone-rich marine units of the Lower Cretaceous (δ<sup>13</sup>C ca. −1 ‰ VPDB) and Upper Cretaceous (δ<sup>13</sup>C ca. −10 ‰ VPDB) during shallow subsurface circulation of meteoric waters through the bedrock. The carbon isotopic composition of the deposits resembles those of endogenic travertines (δ<sup>13</sup>C<sub>trav</sub> −1.2 to 5.3 ‰ VPDB), with the highest δ<sup>13</sup>C<sub>trav</sub> values associated with carbonates from the vents. However, the involvement of deep CO<sub>2</sub> sources is unclear and epigenic processes capable of producing the observed <sup>13</sup>C enrichments are discussed.</div><div>Despite their common sources, similar sedimentological features and δ<sup>18</sup>O<sub>trav</sub> compositional range (−12.4 to −10.1 ‰ VPDB), the δ<sup>13</sup>C<sub>trav</sub> values are lower in the south-facing travertine (−1.2 to 1.9 ‰ VPDB) compared to the north-facing travertine (1.8 to 5.3 ‰ VPDB). This disparity is inferred to result from variations in local environmental conditions due to different levels of insolation, which favored the incorporation of soil-derived CO<sub>2</sub> in the south-facing travertine and likely increased photosynthetic productivity in the north-facing travertine, thereby shifting their δ<sup>13</sup>C<sub>trav</sub> signatures to lower and higher values, respectively. These relationships highlight the sensitivity of low-temperature spring carbonates to subtle environmental changes at basin scales.</div","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"473 ","pages":"Article 106758"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553151","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 : 2024-11-01DOI: 10.1016/j.sedgeo.2024.106767
Katherine Thue , Luis A. Buatois , M. Gabriela Mángano , Mateo Ornia
The Furada Formation of Asturias, Spain, represents a clastic shallow-marine unit deposited during the middle Silurian to the Early Devonian. This formation contains abundant evidence of event deposition and non-uniform distribution of bioturbation structures representing a benthic response to multiple stressors. The 170-m-thick succession was measured and described, and the ichnotaxa were recorded and associated with five sedimentary facies. Most shallow-marine environments are characterized by periodic events of environmental disturbance, mainly by episodic deposition, which may be recorded by a change in both the degree of bioturbation and ichnodiversity. The general depositional setting for this formation has been previously interpreted as a wave-dominated and storm-influenced shallow-marine environment. However, sedimentologic features described in this study, such as anomalous heterolithic and mudstone units, representing fluid mud layers, hyperpycnal flow deposits and plume collapse accumulations, suggest the influence of fluvial discharge, making it a more complex depositional setting. The proposed model comprises an inner sandy shoreface belt flanked seawards by a muddy subaqueous delta platform. The trace-fossil assemblages of this formation reflect environmental stress factors introduced by the interplay of storms and fluvial input (e.g., high sedimentation rate, fluctuating hydrodynamic energy, decreased substrate consolidation), resulting in reduced ichnodiversity and low abundance. From an ichnofacies perspective, the shoreface complex is characterized by the Cruziana Ichnofacies, whereas the subaqueous delta platform is represented by the Phycosiphon Ichnofacies. Integration of sedimentologic and ichnologic datasets allows for a refined depositional interpretation of the formation and greater understanding of the environmental diversity of wave-and river-influenced shallow-marine clastic systems, including the responses of the middle Paleozoic shallow-marine benthos to event sedimentation and environmental disturbance. This study is one of the first detailed documentations of the ichnology of subaqueous deltas.
{"title":"Benthic response to event deposition and environmental disturbance in a shoreface to subaqueous delta system: Ichnology of the Silurian-Devonian Furada Formation of Asturias, Spain","authors":"Katherine Thue , Luis A. Buatois , M. Gabriela Mángano , Mateo Ornia","doi":"10.1016/j.sedgeo.2024.106767","DOIUrl":"10.1016/j.sedgeo.2024.106767","url":null,"abstract":"<div><div>The Furada Formation of Asturias, Spain, represents a clastic shallow-marine unit deposited during the middle Silurian to the Early Devonian. This formation contains abundant evidence of event deposition and non-uniform distribution of bioturbation structures representing a benthic response to multiple stressors. The 170-m-thick succession was measured and described, and the ichnotaxa were recorded and associated with five sedimentary facies. Most shallow-marine environments are characterized by periodic events of environmental disturbance, mainly by episodic deposition, which may be recorded by a change in both the degree of bioturbation and ichnodiversity. The general depositional setting for this formation has been previously interpreted as a wave-dominated and storm-influenced shallow-marine environment. However, sedimentologic features described in this study, such as anomalous heterolithic and mudstone units, representing fluid mud layers, hyperpycnal flow deposits and plume collapse accumulations, suggest the influence of fluvial discharge, making it a more complex depositional setting. The proposed model comprises an inner sandy shoreface belt flanked seawards by a muddy subaqueous delta platform. The trace-fossil assemblages of this formation reflect environmental stress factors introduced by the interplay of storms and fluvial input (e.g., high sedimentation rate, fluctuating hydrodynamic energy, decreased substrate consolidation), resulting in reduced ichnodiversity and low abundance. From an ichnofacies perspective, the shoreface complex is characterized by the <em>Cruziana</em> Ichnofacies, whereas the subaqueous delta platform is represented by the <em>Phycosiphon</em> Ichnofacies. Integration of sedimentologic and ichnologic datasets allows for a refined depositional interpretation of the formation and greater understanding of the environmental diversity of wave-and river-influenced shallow-marine clastic systems, including the responses of the middle Paleozoic shallow-marine benthos to event sedimentation and environmental disturbance. This study is one of the first detailed documentations of the ichnology of subaqueous deltas.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"473 ","pages":"Article 106767"},"PeriodicalIF":2.7,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658817","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}
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