Sedimentary Geology最新文献

{"title":"Shaking table simulation of soft sediment deformation structures in lacustrine sediments","authors":"Lianji Liang ,&nbsp;Zhihao Lu ,&nbsp;Qitao Zhang ,&nbsp;Hongshui Tian ,&nbsp;Fuchu Dai ,&nbsp;Hanchao Jiang ,&nbsp;Ning Zhong","doi":"10.1016/j.sedgeo.2024.106756","DOIUrl":"10.1016/j.sedgeo.2024.106756","url":null,"abstract":"<div><div>Soft sediment deformation structures (SSDSs) in lacustrine sediments could record paleoearthquakes in tectonically active areas. However, their interpretations of deformation and triggering mechanisms still exist disagreement due to the lack of understanding of natural formation processes of SSDSs. In this study, two large shaking table experiments of saturated lacustrine sedimentary sequences, including Model 1 (simple stratigraphic system of thick silty-clay and sand layer) and Model 2 (stratigraphic systems of thin silty-clay and sand alternating layers) were carried out at the different peak ground accelerations (PGA) in order to simulate the earthquake-triggered SSDSs on the basis of field investigation in Tashkorgan of western China. The results showed that there were no SSDSs formed at the PGA 0.125<em>g</em>, and the excess pore-water pressure ratio (γ_<em>μ</em>) measured in the sand layer was lower than 0.1; sand volcanos, pipes and sand veins were formed at the PGA 0.25<em>g</em>, and the γ_<em>μ</em> value of the sand layer reached about 0.2 with the maximum liquefied depths of nearly 30 cm, indicating that weak liquefaction occurred in the sand layer; sand volcanos, pipes, sand veins, diapirs, load and flame structures, ball-and-pillow structures, silty-clay deformation structures were formed at the PGA 0.5<em>g</em> and 0.8<em>g</em>, and the γ_<em>μ</em> value of sand layer reached about 0.91 and 0.94 with the maximum liquefied depths of nearly 60 cm and 100 cm, respectively. The γ_<em>μ</em> value of silty-clay layers measured in all the tests was lower than 0.1, indicating that little liquefaction but thixotropy happened in the silty-clay layers. The tests showed that liquefied SSDSs could form at the PGA 0.25<em>g</em>, while thixotropic and gravity-driven SSDSs could form until the PGA reached 0.5<em>g</em>. This study also provided insights for single or closely spaced shaking events being responsible of superposed deformed beds. The simulated SSDSs have striking resemblance to that of ones identified in the field, supporting the earthquake triggering of SSDSs in the Tashkorgan area.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"472 ","pages":"Article 106756"},"PeriodicalIF":2.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419063","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}

{"title":"Ichnological indicators of physico-chemical stresses in wave- to tide-dominated Miocene shallow marine environments (Argentine Patagonia)","authors":"Sergio A. Celis ,&nbsp;Damián Moyano-Paz ,&nbsp;Sebastián Richiano ,&nbsp;José I. Cuitiño ,&nbsp;Francisco J. Rodríguez-Tovar","doi":"10.1016/j.sedgeo.2024.106755","DOIUrl":"10.1016/j.sedgeo.2024.106755","url":null,"abstract":"&lt;div&gt;&lt;div&gt;An integrated analysis of ichnological and sedimentological features in ancient successions provides a robust dataset of high-resolution interpretations of environmental parameters, encompassing both depositional and ecological aspects. By characterising discrete and recurring bioturbation patterns in the Puerto Madryn Formation (Late Miocene, Argentine Patagonia), we arrive at key knowledge about predominant environmental stresses within transgressive phase shallow marine and estuarine systems, shedding light on their palaeoenvironmental implications. Given the inherent complexities of coastal settings, including the challenges posed by omission/erosion surfaces, it becomes imperative to consider the intricate interplay of multiple depositional processes and environmental factors.&lt;/div&gt;&lt;div&gt;Through a detailed integration of sedimentological and ichnological approaches, we discern the establishment of a wave-dominated system overlain by a tide-dominated estuarine system.&lt;/div&gt;&lt;div&gt;The wave-dominated marine system involves tabular bodies extending laterally over tens of kilometres, with upward fining and coarsening successions from the mid- to lower-shoreface to offshore-shelf environments. The influence of waves and tides on these systems is discussed in the absence of physical sedimentary structures and the need to find elements that bring us closer to elucidating whether waves or tidal processes influence shoreface to offshore systems. The ichnological assemblages allow for the characterisation of &lt;em&gt;Cruziana&lt;/em&gt; ichnofacies with proximal (&lt;em&gt;Taenidium&lt;/em&gt; and &lt;em&gt;Thalassinoides&lt;/em&gt;), archetypal (&lt;em&gt;Asterosoma&lt;/em&gt;, &lt;em&gt;Chondrites&lt;/em&gt;, &lt;em&gt;Cylindrichnus&lt;/em&gt;, &lt;em&gt;Ophiomorpha&lt;/em&gt;, ?&lt;em&gt;Rhizocorallium&lt;/em&gt;, &lt;em&gt;Rosselia&lt;/em&gt;, &lt;em&gt;Scolicia&lt;/em&gt;, &lt;em&gt;Sinusichnus&lt;/em&gt;, &lt;em&gt;Siphonichnus&lt;/em&gt;, &lt;em&gt;Teichichnus&lt;/em&gt;, and &lt;em&gt;Thalassinoides&lt;/em&gt;), and distal expressions (&lt;em&gt;Chondrites&lt;/em&gt;, &lt;em&gt;Helicodromites&lt;/em&gt;, &lt;em&gt;Phycodes&lt;/em&gt;, &lt;em&gt;Thalassinoides&lt;/em&gt;, and ?&lt;em&gt;Zoophycos&lt;/em&gt;) in the lower shoreface to lower offshore and transitional settings with the shelf. However, the transition from these deposits to &lt;em&gt;Chondrites&lt;/em&gt;-dominated beds associated with lower offshore to shelf environments—determined by changes in oxygenation, nutrients, and energy conditions—impedes assignment of all the successions to a particular ichnofacies.&lt;/div&gt;&lt;div&gt;The tide-dominated estuarine system features wide, channel-shaped bodies filled with sandy to heterolithic facies, interpreted as intertidal and subtidal deposits. To differentiate between estuary mouths and other settings, the analysis involved characterisation of transgressive and regressive surfaces, ichnological assemblages, and facies distribution, determining net sediment movement—whether landwards or seawards—and its influence on system classification. The ichnological assemblages could be assigned to the &lt;em&gt;Skolithos&lt;/em&gt; (&lt;em&gt;Arenicolites&lt;/em&gt;, &lt;em&gt;Gyrolithes&lt;/em&gt;, &lt;em&gt;Maiakarichnus&lt;/","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"472 ","pages":"Article 106755"},"PeriodicalIF":2.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419011","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}

{"title":"Sediment bypass in a marl-dominated margin of a turbidite system in a narrow basin setting","authors":"Piotr Łapcik","doi":"10.1016/j.sedgeo.2024.106753","DOIUrl":"10.1016/j.sedgeo.2024.106753","url":null,"abstract":"<div><div>Submarine sediment density flows play a pivotal role in transporting clastic material to the deep sea. The volume of sediment they transport, which bypasses a specific point or geographical location, shapes the stratigraphic record of the entire turbidite systems. Hence, recognition of bypass-dominated zones is crucial in facies prediction and understanding the architecture of turbidite systems. This understanding is linked to the economic aspects of exploring hydrocarbon deposits, the occurrence of geohazards that impact submarine infrastructure, the distribution of pollutants, and carbon sequestration.</div><div>In the western part of the Ropianka Fm (Skole Nappe, Polish Outer Carpathians), three bed types showing evidence of sediment bypass were identified in the channel-mouth setting of marl-dominated slope and base-of-slope successions. The varying proportions of these bed types in studied successions and relationship with adjacent facies associations led to the identification of two channel-mouth zones. This study provides insights into deposits with characteristics differing from the previously described channel-mouth setting, evidenced by a significantly lower sand-to-mud ratio and smaller scale of erosional and depositional structures. The reported channel-mouth zones are interpreted as the marginal parts of a channel mouth, formed by subcritical flows. This study broadens the understanding of the channel-mouth setting by introducing dynamic and mud-dominated zones that experience sediment bypass and weak erosion. The identified bed types and typical characteristics of Marginal channel-mouth zones 1 and 2 can serve as a reference for interpreting marginal areas of channel-mouth settings in mud-dominated successions with scattered thin-bedded and coarse-grained deposits in other deep-water basins.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"472 ","pages":"Article 106753"},"PeriodicalIF":2.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142357555","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}

{"title":"A new type of dolomicrite envelope formed in Oligocene lacustrine sediments and its significance for preserving porosity, Bohai Bay Basin, North China","authors":"Caineng Mu ,&nbsp;Xiaobo Huang ,&nbsp;Liya Da ,&nbsp;Anqing Chen ,&nbsp;James G. Ogg ,&nbsp;Huan Lu ,&nbsp;Yuzhu Ge ,&nbsp;Jian Luo ,&nbsp;Siyu Xiong ,&nbsp;Haiyang Cao ,&nbsp;Mingcai Hou","doi":"10.1016/j.sedgeo.2024.106745","DOIUrl":"10.1016/j.sedgeo.2024.106745","url":null,"abstract":"<div><p>Micrite envelopes are common early diagenetic features in marine carbonate grains. Most case studies of micrite envelopes focus on those with calcium-carbonate compositions. This paper documents a new type of lacustrine dolomicrite envelopes, coating both terrigenous grains and bioclasts, which developed in the upper Shahejia Formation of early Oligocene age in the middle of the Bohai Bay Basin. These dolomicrite envelopes on grains in a lacustrine mixed sedimentary environment are puzzling for their formation and linkage with the porosity preservation of porosity among grains. We investigate the microstructure and formation mechanism of these dolomicrite envelopes that coat grains through the study of the mineralogy, petrology and porosity characteristics. These studies show that there are two occurrences of the dolomicrite envelopes, i.e., coating on detrital grains and coating on carbonate grains, with a multi-layer microstructure. A potential two stage model to interpret the formation of dolomicrite envelopes incorporates an initial illite coating followed by dolomite encrustation. The illite coating played an important role in the precipitation of the dolomite. Post-envelope diagenetic processes include sparry cementation and destructive dissolution. The quantitative content of dolomicrite envelopes positively correlates with the preserved porosity, which suggests that their formation contributed to resisting compaction and protecting porosity among grains. Indeed, the dolomicrite envelopes appear to have aided in maintaining a kind of extremely high-quality reservoir for hydrocarbon exploration within the Shahejia Formation of the Bohai Bay Basin. In addition, the coating film seems to be conducive to the exchange of anions, thereby resulting in the dissolution of interior feldspar-, bioclast- or ooid-grains. In summary the Shahejia Formation of the Bohai Bay Basin provides a new type of dolomicrite envelope on grains in a lacustrine setting.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"472 ","pages":"Article 106745"},"PeriodicalIF":2.7,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142239517","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}

{"title":"Carbon–sulfur–calcium isotopic variability of lower Cambrian shale-hosted carbonate concretions: Insights into growth mechanisms and calcium cycling","authors":"Xiqiang Zhou ,&nbsp;Xiyuan Chen ,&nbsp;Tongxuan Du ,&nbsp;Jian Sun ,&nbsp;Dongjie Tang ,&nbsp;Run Li ,&nbsp;Kang-Jun Huang ,&nbsp;Yi Ding ,&nbsp;Daizhao Chen","doi":"10.1016/j.sedgeo.2024.106746","DOIUrl":"10.1016/j.sedgeo.2024.106746","url":null,"abstract":"<div><div>Marine calcium cycling is closely linked with carbon cycling in the ocean, in which authigenic carbonates precipitated in sediments play a non-negligible role. However, calcium cycling during authigenic carbonate precipitation in organic-rich, shaly sediments in geological history remains underexplored. This study focuses on carbonate concretions (aggregates of authigenic carbonates) in the lower Cambrian Niutitang Formation, South China, to provide insights into calcium cycling during their growth. Sedimentological and mineralogical observations suggest that these concretions were formed through concentric growth by authigenic calcite and pyrite precipitation during the early diagenetic stage. Geochemical analyses reveal internal variations in “M-shaped” δ¹³C_carb trends (from −11.9 ‰ to −4.4 ‰) and diverse δ³⁴S_pyr trends (from 4.7 ‰ to 14.0 ‰) along core-to-rim transects. These findings suggest formation through microbial sulfate reduction by organic matter in a shallow depth beneath the sediment–water interface. In contrast to the dynamic δ¹³C_carb and δ³⁴S_pyr variations and multi-stage concentric growth, these carbonate concretions display nearly uniform δ^44/40Ca_carb values (from 0.80 ‰ to 1.03 ‰, average 0.96 ± 0.06 ‰, 1SD) and consistent internal trends, which are further attributed to strongly seawater-buffered porewater calcium geochemistry and small calcium isotope fractionation due to calcite precipitation at slow rates. This study confirms that early diagenetic carbonate concretions in the lower Cambrian Niutitang Formation are characterized by much heavier δ^44/40Ca values compared to coeval shallow platform carbonates. In light of abundant authigenic carbonates observed in the lower Cambrian successions, their roles in calcium isotope mass balance in the early Cambrian ocean warrant further investigation in the future. Therefore, early diagenetic carbonate concretions in black shales could provide valuable insights into porewater and seawater calcium isotope signals, as well as early diagenetic and marine calcium cycling in geological history.</div></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"472 ","pages":"Article 106746"},"PeriodicalIF":2.7,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142324110","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}

{"title":"Organic matter binding detrital grains contributing to ooid formation and small shelly fossil preservation, a case from the middle Cambrian, southern North China","authors":"Yazhou Hu ,&nbsp;Timothy P. Topper ,&nbsp;Junming Zhou ,&nbsp;Zhao Wang ,&nbsp;Bing Pan ,&nbsp;Yue Liang ,&nbsp;Fan Liu ,&nbsp;Zhifei Zhang","doi":"10.1016/j.sedgeo.2024.106740","DOIUrl":"10.1016/j.sedgeo.2024.106740","url":null,"abstract":"<div><p>Siliciclastic grains, characterized by concentrated Al, Si, K and other elements, are typical components of ooids, but their distribution and contribution to ooid formation are uncertain. Coatings have played a significant role in small shelly fossil preservation in early Cambrian phosphate or phosphatic carbonates. However, the relationship between ooid construction and the preservation of small shelly fossils has not been fully elucidated. Herein, we report well-developed flaggy ooids containing siliciclastic grains from a middle Cambrian carbonate–siliciclastic depositional system in North China. We observe that ooids consist of multiple layers of dark and light laminae. The dark laminae with a high organic content and flexible appearance are interpreted as biofilms. The distribution of detrital grains is closely coupled with these dark laminae and the filamentous structures around fossil shells, which indicates that the detrital particles are bound by the biofilms or filamentous structures. The high occurrence and compacted nature of siliciclastic particles observed in these ooids reveal that detrital grains could be the main contributing factor in ooid formation in the middle Cambrian Longwanggou section. Those flaggy ooids composed of clay-size detrital grains finely mimic the shell morphology and microstructure, providing another important window for the preservation of small shelly fossils in the Cambrian.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"472 ","pages":"Article 106740"},"PeriodicalIF":2.7,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0037073824001635/pdfft?md5=ede7a9af10abe03ac7629e4fe103a519&pid=1-s2.0-S0037073824001635-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142151589","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}

{"title":"Grain textural bias in detrital single-mineral provenance studies","authors":"Xiaotian Shen ,&nbsp;Xing Jian ,&nbsp;Wei Zhang ,&nbsp;Ping Guan","doi":"10.1016/j.sedgeo.2024.106731","DOIUrl":"10.1016/j.sedgeo.2024.106731","url":null,"abstract":"<div><p>Detrital single-mineral geochemistry and geochronology are strong tools in provenance studies and indicate great potentials in addressing issues in earth sciences. Various biases (both natural and artificial) exist objectively and may mislead provenance interpretations. Both the sedimentary sorting process and hand-picking in-laboratory processing may lead to analyzed grain textural (e.g., size and shape) variability and thus may introduce biases in single-mineral provenance analysis. Here, we take the Mesozoic–Cenozoic Qaidam basin, northeastern Tibet, as an example to investigate the relationship between single-mineral grain texture and detrital zircon geochronological and detrital tourmaline, rutile and garnet geochemical data and to explain how grain texture affects detrital single-mineral provenance interpretations. Results indicate that Precambrian zircons take less proportions in coarse (&gt;125 μm), subrounded and high aspect ratio (&gt;2) fractions than Phanerozoic zircons. Parent rock lithology discrimination results of detrital tourmaline and garnet in different grain size fractions show significant differences. Zr-temperature values of detrital rutile have an increasing trend with increasing grain size. The geochemistry of detrital tourmaline, rutile and garnet shows no dependence with grain aspect ratio and roundness. We suggest that inheritance of grain texture features from parent rocks is the major reason. Detrital zircons from recycled (meta)sedimentary rocks tend to be smaller and more rounded than those from igneous rocks. Detrital tourmaline, rutile and garnet grains from different parent rock types vary in size. Grain textural bias may cause the underestimated contributions of the Qilian Shan to the Cenozoic Qaidam basin if small detrital zircons were not involved in the analysis. Quantitative description of the source-to-sink system of the Cenozoic Qaidam is also influenced by grain textural bias. This study highlights the underestimated grain textural bias in single-mineral provenance studies. We suggest that a comprehensive understanding of potential sedimentary sources, depositional processes, sample petrographic features and laboratory analysis procedures is important to reliable provenance interpretations and to related implications in earth sciences.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"471 ","pages":"Article 106731"},"PeriodicalIF":2.7,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142128754","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}

{"title":"Microbial micritic cementation in deep time: Implications for early marine lithification and paleoenvironmental reconstruction","authors":"Salim Belkhedim ,&nbsp;Gregor P. Eberli ,&nbsp;Matthias López Correa ,&nbsp;Radouane Sadji ,&nbsp;Abdelkrim Nemra ,&nbsp;Miloud Benhamou ,&nbsp;Axel Munnecke","doi":"10.1016/j.sedgeo.2024.106727","DOIUrl":"10.1016/j.sedgeo.2024.106727","url":null,"abstract":"<div><p>Early micritic cementation is important to reconstruct paleoenvironments of sedimentary gaps. However, due to their scarcity in ancient records, their initial mineralogy (low-magnesium calcite (LMC), high-magnesium calcite (HMC), aragonite), as well as their origin (biotic or abiotic) and paleoenvironments are still controversial. Herein, based on fluorescence microscopy (FL), cathodoluminescence microscopy (CL), and microdrilling carbon and oxygen isotope analyses, we investigate well developed micritic cements in lower Pliensbachian limestones from the Traras Mountains, northwestern Algeria. Evidence for a microbiological influence in the formation of these cements is given by their irregular morphology, the presence of clotted micropeloidal structures, as well as their bright fluorescence under FL. Together, they reflect precipitation of the micritic cements under microbial control via active and/or passive mechanisms, in the presence of organic matter. Their orange luminescence and low δ¹⁸O signals suggest their initial precipitation by sea-water as HMC before being recrystallized into LMC within the meteoric and/or burial realm. These micritic cements, including anisopachous and meniscus-like cements are thought to be precipitated within the marine phreatic zone, as they are associated mainly with isopachous fibrous cements, which is in contrast to their widespread attribution as typical and indicative fabrics of the marine vadose zone. In addition, it has been shown that crystalline cements are developed always upon the early micritic envelopes and micritic cements. These observations which are in line with recent studies conducted on modern deposits confirm that preservation of marine microbial cements in deep time is crucial not only for early grain stabilization, but also serving as a foundation for the subsequent crystal growth.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"471 ","pages":"Article 106727"},"PeriodicalIF":2.7,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141931472","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}

{"title":"The hypertidal Santa Cruz–Chico River estuary (South Patagonia, Argentina): A hybrid ria-type system under extreme tides, arid climate and active uplift","authors":"Bernadette Tessier ,&nbsp;Jean-Yves Reynaud ,&nbsp;Jose I. Cuitiño ,&nbsp;Roberto A. Scasso ,&nbsp;Léo Pancrazzi ,&nbsp;Maria Duperron ,&nbsp;Pierre Weill ,&nbsp;Viviane Bout-Roumazeilles ,&nbsp;Eric Armynot du Châtelet ,&nbsp;Anjana Kuinkel ,&nbsp;Thibaud Lortie ,&nbsp;Laurent Dezileau","doi":"10.1016/j.sedgeo.2024.106728","DOIUrl":"10.1016/j.sedgeo.2024.106728","url":null,"abstract":"<div><p>The present study focuses on the morphosedimentary organization and sediment infilling stratigraphy of one of the largest estuaries of southern Patagonia in Argentina. With a tidal range up to 12 m, the area is subject to extreme tidal conditions, combined with moderate offshore wave climate, strong and constant westerly winds, and contrasted water and sediment discharges from the two tributaries of the estuary, the Santa Cruz and Chico rivers. The estuarine valley is entrenched in the Patagonian coastal plateau due to significant uplift. On the basis of sediment facies (sedimentary structures, grain size, geochemistry, mineralogy), meiofauna (foraminifera and testate amoebae), morphological changes and shallow geophysics (high-resolution seismic reflection, ground-penetrating radar) data, the Santa Cruz–Chico River system is defined as a hybrid system comprising a tide-influenced fluvial mouth (the Santa Cruz River) and a tide-dominated estuary (the Chico River estuary), both converging toward an elongated subtidal ria-type estuarine basin. River-supplied sands and muds by-pass the estuarine basin and are exported offshore where they settle and form an ebb-tidal delta. Sediments in the Santa Cruz–Chico River valley mainly consist of Pleistocene lowstand fluvial gravels resting on the regional Miocene substrate, and thin early Holocene transgressive deposits, deeply incised by a tidal ravinement surface that developed during the highest Holocene sea-level at ca 7500 y. BP. After the maximum stillstand, relative sea level fell and a competition occurred between erosion, promoted by water depth decrease, and deposition, favored by tidal prism reduction. At present, sediment by-passing and offshore sediment export are the dominant processes. The very large size of the ebb-tidal delta, which expands on the continental shelf, suggests that this situation has prevailed for a very long time.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"471 ","pages":"Article 106728"},"PeriodicalIF":2.7,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0037073824001519/pdfft?md5=9eb2c7e267f7c94f983c1f187f3d895a&pid=1-s2.0-S0037073824001519-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142095196","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}

{"title":"Microbial and hydrothermal dolomite formation in Early Cretaceous lacustrine sediments in Yin'e Basin: Insights from petrology and geochemistry","authors":"Kun Zhang ,&nbsp;Ziping Liu ,&nbsp;Zhitao Xu ,&nbsp;Qing Chang ,&nbsp;Douaa Fathy ,&nbsp;Rong Liu ,&nbsp;Edith Bai","doi":"10.1016/j.sedgeo.2024.106739","DOIUrl":"10.1016/j.sedgeo.2024.106739","url":null,"abstract":"<div><p>Dolomite is widely present in geological history, but its origin has always been a prominent problem that troubles sedimentologists. For lacustrine dolomite, current research has not yet provided a reliable explanation for its complex genesis mechanism. The Early Cretaceous lakes in Northwest China host various morphological dolomites, providing valuable materials for exploring the origin of dolomites. According to their petrological and mineralogical characteristics, it can be divided into thick laminated dolomite, thin laminated dolomite, dolomitic mudstone, and vein dolomite. The ratios of trace elements and rare earth elements show that these dolomites precipitated in a brackish–suboxic environment. The high δ¹³C values (&gt;8 ‰VPDB) of thick laminated dolomite and some thin laminated dolomite suggest the involvement of methane-producing microorganisms in the precipitation of dolomite, and the appearance of microscale/nanoscale spherical dolomite aggregates and the dispersed organic matter around dolomite particles jointly confirm that microbial-mediated biological activity promotes dolomite precipitation. The dolomite stoichiometry (mole % MgCO₃) confirms that thick laminated dolomite was deposited in a restricted shallow water environment, while dolomitic mudstone is mainly deposited in relatively open water areas. The thin laminated dolomite in the shale laminae represents short-term or seasonal climatic and environmental fluctuations. In addition, some carbonate minerals of dolomitic mudstone in shallow water environment recrystallized by post-depositional hydrothermal effect, resulting in δ¹⁸O value decreased (&lt;−10 ‰VPDB). The vein dolomite is characterized by high rare earth content and low δ¹³C and δ¹⁸O values, and its Sr isotope (0.712894 ± 0.000374) values reflect that the hydrothermal fluid may have been formed by the mixing of infiltrating lake water and crustal magmatic water. According to the characteristics of fluid inclusions, it is inferred that the hydrothermal fluid has the characteristics of low temperature (108.3 °C–159.8 °C), medium salinity (3.5 wt%–14.3 wt% NaCl) and high density (0.95–1.00 g/cm³). The microbial mediation and tectonic hydrothermal fluids play an important role in the formation of the Early Cretaceous lacustrine dolomite.</p></div>","PeriodicalId":21575,"journal":{"name":"Sedimentary Geology","volume":"471 ","pages":"Article 106739"},"PeriodicalIF":2.7,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142150012","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}