Evolution Of Sedimentary Environments Research Articles

Coupling of Paleosedimentary Environment and Lithofacies: Implications for Shale Oil Enrichment in the Lianggaoshan Formation, Northeastern Sichuan Basin, China.

The sedimentary environment is paramount in dictating depositional processes, ecological settings, and hydrodynamic conditions, all of which are pivotal to the aggregation of organic-rich sediments. A synergistic interplay is observed among the paleosedimentary environment, lithofacies, and enrichment of shale oil. Utilizing an analysis of elemental geochemistry and organic geochemical parameters-such as total organic carbon (TOC) content-this study endeavors to identify the predominant factors that govern the enrichment of organic matter (OM). It reconstructs the evolutionary trajectory of the paleosedimentary environment and introduces a dynamic model for shale oil enrichment within the Jurassic Lianggaoshan Formation of the Sichuan Basin. The results indicate that the Lianggaoshan Formation shale can be categorized into five lithological types, including high TOC felsic-rich shale (A), moderate TOC felsic-rich shale (B), moderate TOC felsic-rich mudstone (C), low TOC felsic-rich shale (D), and low TOC felsic-rich mudstone (E), and high TOC felsic-rich shale has the highest TOC and oil content. The shales of the Lianggaoshan Formation were deposited in an environment characterized by abundant terrestrial input, humid climate, freshwater conditions, reduced oxygen levels, and thriving primary productivity. OM enrichment is mainly controlled by the combination of a humid paleoclimate, high primary productivity, and other factors. The paleoenvironment deposited by lithofacies A coincides with the paleoenvironment conducive to OM enrichment, which makes lithofacies A become the dominant lithofacies for shale oil enrichment. Additionally, the sedimentary environment evolution characteristics and shale oil enrichment model of the Lianggaoshan Formation were established based on geochemical parameters. The paleosedimentary environment of the Lianggaoshan Formation from bottom to top is more and more unfavorable. The No.1 submember of the Lianggaoshan Formation is the most potential shale submember for shale oil exploration due to the paleosedimentary environment that promoted the deposition of lithofacies A and OM enrichment.

Evolution of black shale sedimentary environment and its impact on organic matter content and mineral composition: a case study from Wufeng-Longmaxi Formation in Southern and Eastern Sichuan Basin

Due to global geological events and differences in regional sedimentary environments, marine shale reservoirs of Wufeng-Longmaxi Formation in Eastern and Southern Sichuan Basin exhibit significant heterogeneity in organic matter content and mineral composition. In order to reveal the influence of paleoenvironment evolution on reservoir heterogeneity, key geochemical indicators of elements were used to reconstruct the sedimentary environment of marine shale in Eastern and Southern Sichuan Basin. The influence mechanism of paleoenvironment on organic matter content and mineral components was also explored. The results indicate that the Wufeng-Longmaxi Formation in the Southern and Eastern Sichuan Basin can be divided into two third-order sequences (Sq 1 and Sq 2). Each third-order sequence is divided into a transgressive system tract (TST) and a highstand system tract (HST). The average TOC content in the Eastern Sichuan Basin is the highest during the TST1 period with reaching 4.2%, while reached its maximum at 3.9% during the TST2 period in the Southern Sichuan Basin. Due to the influence of high paleo-productivity, the organic matter accumulation and quartz content in the eastern Sichuan region were higher than those in the southern Sichuan region from the TST1 to the middle TST2 period. However, the organic matter accumulation and quartz content in the late TST2 period were lower than those in the southern Sichuan region due to the dilution of terrestrial debris. During the HST2 period, due to the influence of higher paleo-productivity, clay adsorption and preservation condition, the TOC content in the eastern Sichuan region slightly increased in the early stage. At the same time, the marine shale in the southern Sichuan region has a high content of quartz minerals and a low content of clay minerals due to strong weathering intensity and input of coarse-grained debris (silt-size quartz).

Sedimentary evolution and distribution of benthic fauna of an Aptian protected bay (Oliete Subbasin, Spain)

Detailed facies and sequence stratigraphic analysis of an Aptian shallow-marine succession illustrates the evolution of sedimentary environments and their benthic faunal associations in a marginal bay developed in northeastern Iberia (Maestrazgo Basin, Oliete Subbasin). In this bay, marine circulation was hampered by wide stationary shoals located in the low-subsidence transitional areas between subbasins. The Aptian sedimentary record of this bay (Josa and Oliete formations) is composed of four transgressive–regressive (T–R) sequences bounded by major unconformities generated during relative sea-level falls. The Josa Fm (formally defined herein) encompasses an asymmetrical T–R cycle (sequence J). It comprises transgressive prodelta clays with episodic orbitolinid blooms, grading upwards to regressive freshwater-influenced littoral and delta-front sandstones and sandy limestones which yield diverse bivalve communities dominated by trigoniids. The Oliete Fm encompasses three T–R cycles (sequences O1–O3), mostly deposited in a protected lagoon. The transgressive hemicycle of each sequence is dominated by marls containing low-diversity faunal associations composed of ostracods and mm-sized gastropods and bivalves, indicating stressed (probably dysoxic) conditions in the deepest parts of the lagoon, related to a lack of water circulation. The regressive hemicycle of sequences O1 and O2 is characterised by low-energy intertidal to shallow subtidal deposits including sponge spiculites, mud-dominated accumulations of articulated bivalves and gastropods with low-diversity microfaunal associations composed mainly of Choffatella and few other textulariids, and marginal oyster-serpulid patches. The uppermost part of sequence O2 is characterised by the development of siliciclastic tide-influenced coastal plains. Sequence O3 consists of massive intertidal to shallow subtidal glauconite accumulations related to the transgressive reworking of siliciclastic deposits. Foraminiferal associations in sequence O3 show an increase in diversity (including miliolids, lageniids and diverse textulariids), which was probably fostered by a more stable connection with open seas, caused by tectonic activity in the bounding shoal areas. The analysis of these four sequences represents a comprehensive and detailed characterisation of shallow-to-marginal marine benthic communities integrated in a sequence stratigraphic framework.

Evolution of sedimentary environment in the Eastern Henan Basin since the Late Pliocene

The Eastern Henan Basin is situated within the downstream alluvial plain of the Yellow River, harboring an impressive accumulation of over 500 m of fluviolacustrine strata since the Pliocene. However, the evolutionary characteristics and driving factors of the sedimentary environment in this region remain unclear due to a lack of reliable chronological constraints on the sedimentary sequence. Here, two cores were retrieved from Hangkonggang (HKG, 303.5 m) and Baisha (BS, 320.2 m) in the Eastern Henan Basin for comprehensive analyses of chronology and sedimentology. A combination of paleomagnetism, electron spin resonance (ESR), and optically stimulated luminescence (OSL) dating results indicates that sediments of two boreholes were accumulated spanning the last ∼3.48 Ma. Grain size distributions (GSDs) of typical sedimentary facies show that the boreholes predominantly encompass three types of sedimentary facies: riverbed, levee, and floodplain. Downcore variations of mean grain size (MGS) reveal that the sedimentary environment in this basin evolved from a dominant riverbed setting during the late Pliocene (3.48–2.72 Ma) to alternations between the floodplain and levee facies during the early Pleistocene (2.72–1.25 Ma) and subsequently between the riverbed, levee, and floodplain after 1.25 Ma. It was closely associated with the decrease in East Asian monsoon precipitation at ∼2.72 Ma and the increase at 1.25 Ma. Notably, the abrupt coarsening of MGS after ∼1.25 Ma was synchronized with the formation of the Sanmenxia terraces, implying the significant influence of the evolution of the Yellow River. Our results suggest that the sedimentary environment of the Eastern Henan Basin was predominantly affected by the stepwise evolution of the East Asian monsoon since ∼3.48 Ma and complementary landform transformation of the Yellow River since at least ∼1.25 Ma.

Variable depositional environments and organic matter enrichment of Early Cambrian shales in the Middle Yangtze region, South China

Organic-rich shales of the Lower Cambrian Shuijingtuo Formation (SJT) in the Middle Yangtze region (South China) represent an important target for shale gas exploration and development in China. The lower section of the SJT mainly consisting of organic-rich black shale deposits has been regarded to be a favorable target for shale gas exploration and received substantial attentions, while the upper section of the SJT primarily consisting of limestone, silty shale and black shale deposits has been rarely studied. Most recently, a major breakthrough of shale gas exploration and development has been made in the upper section shale deposits. In order to better understand the redox evolution of sedimentary environment throughout the whole Early Cambrian time and organic matter (OM) enrichment mechanism of the SJT shale deposits, geochemical investigations, including analyses of total organic carbon (TOC), as well as major and trace element compositions, were conducted on the upper section of the SJT shales from Well EYY1. Our results showed that the upper section of the SJT shale deposits was accumulated during the Cambrian Stage 3. The TOC values of the studied SJT shale samples ranged from 0.34 to 3.65 wt%. The lower part of the upper section of the SJT shale, which exhibited relatively high TOC contents (∼2.0 wt%), was deposited under anoxic bottom-water conditions during the early Cambrian Stage 3, while the upper part, showing relatively low TOC content (1.0 wt%), was deposited under suboxic bottom-water conditions with intermittent episodes of anoxic bottom-water conditions during the middle–late Cambrian Stage 3. The palaeo-productivity of the SJT shale was estimated to be generally low, and displayed little variation. The OM enrichment mechanism of the SJT shale deposits underwent dynamic changes due to relative sea-level changes in the Yangtze Ocean. The OM enrichment of the early and late Cambrian Stage 3 shale deposits was primarily controlled by reducing conditions, while that of the middle Cambrian Stage 3 shale deposits may have been influenced by episodic upwelling activities.

Sedimentary processes of the Lower Permian Dingjiazhai Formation in the Baoshan Block

The Baoshan Block was part of the eastern Cimmerian continent along the northeastern margin of Gondwana during the late Paleozoic, and preserves continuous sedimentary records during the apex of the Early Permian glaciation. Although much work has been carried out on biostratigraphy and paleogeography, detailed sedimentological study of the glacial records in the Baoshan Block has gained little attention, which hampers the understanding of depositional processes along the northeastern margin of Gondwana. Here, we conduct a high-resolution sedimentological study on the Lower Permian Dingjiazhai Formation of the Baoshan Block, with the aim of reconstructing the evolution of sedimentary environments. Six major lithological facies and three facies associations are recognized from the Dongshanpo section. The diamictite facies association is composed of weakly stratified diamictite, stratified diamictite, and massive sandy siltstone facies, which are formed by proglacial outwash debris flows and settling of melt-water plumes. The lenticular gravelly sandstone facies association consists of lenticular gravelly sandstone, thin-bedded siltstone, and homogenous silty mudstone facies, suggesting a distal subaqueous proglacial offshore setting with episodic melt water plumes. The bioclastic rudstone facies association comprises of bioclastic rudstone and floatstone, and thin-bedded siltstone facies, which suggest an offshore depositional environment punctuated by bioclastic gravity flows. Accordingly, we reconstructed a gradually changed sedimentary model responding to the Early Permian deglaciation in the Baoshan Block, which probably represents a typical evolution of sedimentary environments along the northeastern margin of Gondwana during the Early Permian.

Sedimentary facies and environmental evolution of the alluvium in the Iriai lowland, Oga Peninsula

男鹿半島北岸，五里合低地で掘削された6本の沖積層ボーリングコアの層相解析，放射性炭素年代測定，珪藻化石分析および花粉化石分析に基づいて，堆積盆の基盤を構成する地層，堆積盆の埋積過程と完新世の環境変遷を検討した．五里合低地では，約15～20 mの厚さの沖積層が，最終氷期の堆積面が削剥されて形成された幅広い堆積盆を埋積している．堆積盆の基盤は，上部更新統潟西層の砂層および約40,000年前の湿地堆積物からなる箱井層最下部である．五里合低地の環境は，後氷期の温暖化による海進の影響よって，扇状地から約10,000年前には氾濫原となり，8,500年前には湾となった．縄文海進高頂期には，汽水あるいは海水の影響を受ける淡水の水域に変化した．その後，海退に伴うデルタの前進によって水域は南から次第に縮小し，3,000年前ごろには全域が湿地となり，次第に乾燥化して現在のような低地に変化した．

A research on excavation compensation theory for large deformation disaster control and a review on the multiphysical–multiscale responses of salt rock for underground gas storage

A research on excavation compensation theory for large deformation disaster control and a review on the multiphysical–multiscale responses of salt rock for underground gas storage

Evolution of sedimentary dynamic process/pattern in the Quanzhou Bay under impact of Typhoon Matmo (2014)

Typhoons are one of the most dramatic weather events affecting the nearshore environment, which significantly affect the processes of sediment erosion, transport, and redeposition in a short period of time. In this study, the hydrodynamic evolution and sedimentary source and sink processes in the Quanzhou Bay after the typhoon’s passing were systematically studied by using the water column observation data (flow field and turbidity) and the surface sediment grain-size analysis results obtained in two surveys: 3–4 days and 1 month after Typhoon Matmo (2014), respectively. The results show that the typhoon process significantly increased the sediment flux input from the Jinjiang River and expanded the sediment “sink” in the Jinjiang River estuary. After the typhoon’s passing, the sediments in the bay were redistributed under the stable tidal transport, and the estuarine sediments were transformed from a sink of riverine material into a source of sediment transport and diffusion. Typhoon processes play an important role in the evolution of estuarine sediments and sedimentary environment.

Late Pleistocene sedimentary environment reconstruction and evolution in the Houtao Plain

Reconstructing the Late Pleistocene sedimentary environment history of the Houtao Plain has great significance not only for revealing the evolution of the Yellow River but also for identifying the formation of paleolake and the northern Ulan Buh Desert. This paper presents the results of the sedimentary facies framework based on a grain-size multi-parameter analysis optically stimulated luminescence and 14C dating for a drilling core DKZ06 with a length of 20.04 m from the Houtao Plain. Grain-size multi-parameter analysis was combined with the grain size of modern environmental sediments to the division of the core sedimentary facies in this area. Sedimentary facies of core DKZ06 indicate that the formation of the Houtao Plain area is dominated by fluvial channel deposition and river changed mainly by frequent fluvial channel since ∼35 ka. The two episodes of shallow lake deposition from a drilling core, suggesting that there will not be a mega-paleolake in the Houtao Plain, and the frequent channel migration of the Yellow River may have caused a series of furiotile lakes during the Late Pleistocene. The appearance of aeolian sand at the top of core DKZ06 combined with previous stratigraphic records from the adjacent areas indicates that the origin of the northern Ulan Buh Desert is relatively late and it formed only 2,000 years ago. We propose that a combination of river migration and large-scale human activity may be responsible for desert formation. The evolution of sedimentary environments has a close correlation with climate change during the Late Pleistocene. During the interglacial stage (MIS3), the sedimentary environment has a particular lacustrine and fluvial–lacustrine environment because of relatively warm–humid conditions. During the glacial stage (MIS2), the Houtao Plain was dominated by a fluvial sedimentary environment because of a relatively cold and dry climate. The sedimentary environment is complex and changeable during the Holocene (MIS1), which was likely due to the frequent climate fluctuation.

Influence of Sedimentary Environment Evolution on Fingerprint Characteristics of Methane Isotopes: A Case Study From Hangzhou Bay

AbstractTo better understand the depositional constraints on the fingerprint characteristics of methane isotopes, we present a set of carbon/hydrogen isotopic data for CH4, CO2, pore water, carbonate, and total organic carbon along a 70‐m sedimentary core. The sedimentary facies (Units I, II, and III from upper to bottom) suggested depositional environments of the present estuary, shallow marine, and floodplain‐estuary. Calculations suggested that around 86% of methane was produced through the CO2 reduction pathway. In this pathway, the hydrogen in CH4 is from ambient water, while the carbon is from dissolved inorganic carbon. Correspondingly, our study showed that the values of δDCH4 displayed similar trends with those of δDH2O and Cl− concentrations along the depth profiles. The low δDCH4 below 44.5 m corresponded to low δDH2O and low salinity during the cold and low‐sea‐level period. The values of δ13CCH4 generally synchronously changed with those of δ13CCO2. The variation trends of δ13CCH4 and δ13CCO2 were the same with δ13Ccarbonate from 10 to 70 m depth but decoupled above 10 m. The values of δ13CCH4 in Units II and III were correlated with the δ13Ccarbonates, which is related to the sedimentary processes. But decoupling of low values of δ13CCH4 and δ13CCO2 from δ13Ccarbonates in Unit I may be related to preferential microbial consumption of labile compounds with light carbon isotopic compositions, such as lipids. In short, the variations of δ13CCH4 and δDCH4 were largely related to the sedimentary process, which controlled the isotopic compositions of both water and carbonate.

Sedimentary records and implications for the evolution of sedimentary environments inferred from BH1302 during the late Quaternary in the Bohai Sea, China

Under the influence of glacial-interglacial climate change and regional tectonic activities in the Quaternary, the sedimentary environments of the Bohai Sea changed greatly, providing significant information on transgression-regression events, East Asian monsoon changes and regional tectonic activities. This study analyzed the sedimentological characteristics of the BH1302 core (water depth of 12.3 m, length of 70.2 m) in the southern Bohai Sea based on grain size, foraminiferal assemblages, carbon and oxygen isotopes in foraminiferal shells and element geochemistry, and established a chronological framework based on AMS 14C, optically stimulated luminescence dating and Oxcal age-depth model using Bayesian modeling. The results showed that three interglacial transgressions and one interstadial transgression were revealed in BH1302 since the late Quaternary, corresponding to marine isotope stages (MIS) 7, 5, 3 and 1, and three subinterglacial transgressions were further identified during MIS 7. The sedimentary environments of Laizhou Bay transitioned from an estuary environment dominated by rivers to a neritic environment dominated by marine conditions because of subsidence of the Miaodao uplift in late MIS 7.1. Three subinterglacial transgressions occurred in MIS5 and two subinterstadial transgressions in MIS 3, and the highstand sea level of MIS 3 reached approximately −18 ∼ −21 m. Under the influence of sea level fluctuations and the East Asian monsoon, the sedimentary environments of MIS 1 can be divided into a low salinity tidal-flat environment (12.0–7.0 kyr BP), a low salinity neritic environment (7.0–4.5 kyr BP) and a modern neritic environment (∼4.5 kyr BP).

Reconstruction of the sedimentary environment of phytogenic deposits in the Tomisławice opencast mine (Konin Region, central Poland)

Palynological analysis of the Tomis³awice opencast mine deposits has allowed reconstruction of the plant communities and investigation of the evolution of sedimentary environments at various stages of lignite-forming marsh development, recorded in the composition of pollen assemblages from deposits of the 1st Mid-Polish lignite seam (MPLS-1). Rich pollen communities from an ~9 m thick section has enabled study of the succession of plant communities and of the evolution of phytogenic sedimentation. The pollen succession indicates that the assemblages in the whole lignite seam represent the VIII Celtipollenites verus pollen Zone. Slight differences in the composition of the communities reflect different stages of basin development, depending more on the variable water dynamics than on climatic oscillations. Lignite of the MPLS-1 developed in a continental regime on alluvial plains. Changes in the succession of plant communities in the Tomis³awice section record flooding-drainage cycles caused by groundwater level oscillations. Peat bog accumulation took place in river basins, in which the lack of siliciclastic intercalations within the massive lignite seams points to weak fluvial dynamics. A rise in groundwater level and/or surface water resulted in flooding of the marshes and the formation of an extensive shallow lake basin, as shown by the presence of freshwater algae and pollen of aquatic plants. The section as a whole does not record an increased contribution of thermophilic plant taxa. The flora was generally dominated by warm-temperate and thermophilic species, without the participation of strongly thermophilic vegetation, which indicates that the lignite seam in the Tomis³awice opencast mine was formed in the generally stable conditions of a warm temperate climate.

Early to mid-Holocene sedimentary environmental evolution in the palaeo-Ningbo Bay, East China and its implications for Neolithic coastal settlement

The Ningbo Plain on the East China coast is an important center of Neolithic culture, and associated settlements were influenced by changing sea levels and the geomorphological and hydrological environments of the palaeo-Ningbo Bay, the details of which are still subject to debate. This study is based on two well-dated sediment cores obtained from the Ningbo Plain, and here we report analyses of their sedimentology and foraminifera to reveal the infilling history of the palaeo-Ningbo Bay and its association with Neolithic occupation. The lithology of the largely muddy sediments and the dominance of euryhaline and brackish water foraminiferal species are indicative of an intertidal to a subtidal environment in the palaeo-bay during the early to mid-Holocene. Abrupt coarsening of sediment grain size and a corresponding increase in the abundance of foraminiferal species of inner and middle shelf environments occurred at ca. 8.8 cal. kyr BP and 7.6 cal. kyr BP, reflecting two major events of strengthened marine transgression that correspond to the rapid global sea-level rise events of Meltwater pulses (MWPs) 1C and 1D, respectively. A marked increase in the relative abundance of Ammonia annectens and Ammonia compressiuscula during ca. 7.5–7.1 cal. kyr BP further indicates frequent storm surges at that time. Between the two rapid transgression events, aggradation of tidal flats prevailed after ca. 8.0 cal. kyr BP, which provided a suitable setting for Neolithic settlements, as indicated by the recently discovered Jingtoushan site. However, the transgression sequence associated with the latter, the MWP-1D event, caused a regional cultural interruption at ca. 7.6 cal. kyr BP. Infilling and coastal marsh development in the palaeo-Ningbo Bay occurred progressively after ca. 7.0 cal. kyr BP and are associated with the emergence of the Hemudu culture.

Provenance of sediments from the Niger Delta, Gulf of Guinea: Evidence from geochemistry

The Gulf of Guinea is surrounded by numerous waterways, where several rivers flow into the ocean, and the Niger River brings large amounts of land-derived debris into the Niger Delta every year. However, geochemical characteristics and sources of sediments in this region are still poorly constrained. Here, we collected two cores (GC09 and GC10) on the shelf and one core (GC05) on the shelf break of the Niger Delta, Gulf of Guinea to assess their provenance using total carbon (TC), total organic carbon (TOC), major elements, and trace elements. The results indicate that sediments on the Niger Delta are classified as iron-rich silty clay and silty clay based on their geochemical compositions. Surface sediments are enriched in quartz and feldspar, evidenced by relatively high levels of SiO 2 , Al 2 O 3 , NaO 2 , K 2 O and CaO. Trace element ratios and TOC demonstrate organic matters were mainly derived from terrestrial inputs and were deposited under aerobic conditions. Geochemical index data (TOC, REEs, δCe, δEu) reflect that the redox conditions of deposition are more inclined to aerobic environment; the sea level gradually decreased and induced more oxic depositional environment over time. According to the location of the three sampling sites, the proportion of felsic in the provenance of sediments increased towards the mainland while the proportion of mafic decreased. With the increasing of water depth, the proportion of felsic source decreases from ~67% at GC10 site (Water depth is 1418 m) to ~50% at GC05 site (Water depth is 3245 m). In contrast, the proportion of mafic source increase from ~25% at GC05 site to ~50% at GC09 site (Water depth is 1377 m). Using chemical index of alteration (CIA), it is manifested that the sediments show high maturity and have experienced strong chemical weathering. Statistical analyses indicate terrigenous inputs contribute more than half materials for the Niger Delta sediments. The relatively stable depositional environment in this region favors the formation and development of gas hydrates. This study could be used to infer the sediment sources and paleoenvironment changes during sedimentation and also provide reliable information for a better understanding of sedimentary processes in global gas hydrate-related deltas. • Provenance of marine sediments in Niger Delta, Gulf of Guinea by geochemistry methods. • The evolution of sedimentary environment in the Niger delta region. • Inorganic geochemical signatures of marine sediments from where gas hydrates can form.

Lipid Biomarker and Stable Isotopic Profiles through Late Carboniferous–Early Triassic of the Deepest Well MS-1 in the Junggar Basin, Northwest China

The Carboniferous–Triassic period was an important stage of global sea–land transformation, with coal formation in the Carboniferous, biological extinction at the end of the Permian, and global drought in the Triassic. The MS-1 well in the Mosuowan High of the Junggar Basin is the deepest well drilled in Northwestern China. In this paper, we investigate the sedimentary environment and climate evolution of the Mosuowan area in the central Junggar Basin during the Late Carboniferous–Early Permian by the petrothermal, lipid biomarker, and isotopic composition of mud shale core samples, and explore the tectonic–climatic events and Central Asian orogenic belt evolution driving the sedimentary environment. The study shows that the organic matter from the Upper Carboniferous to the Lower Permian is at a mature stage, but biomarkers maintained the primary information although the organic matter was subjected to thermal evolution. In the late Carboniferous period (Tamugan Formation), the study area was a closed remnant sea with a relatively humid climate, triggering lush terrestrial vegetation and high organic carbon content in the sediments, which had the potential to evolve into natural gas. During the Xiazijie Formation of the Middle Permian, tectonic activity shifted to the subsidence period, and the salinity of the water decreased after a large input of fresh water. The lake basin area expanded, and the content of aquatic organisms continued to increase. As the Lower Permian stratigraphy is missing, this sea–land transition seems to jump. The low and upper Urho Formations of the Middle–Upper Permian are a deltaic foreland deposit, and geochemical indicators show an overall lake retreat process with a continuous increase in organic matter content of terrestrial origin. The lithologic assemblage of the Triassic Baikouquan Formation is braided river deltaic sedimentation with migration of deposition centers of the lake basin. In conclusion, the Late Carboniferous–Early Permian period was influenced by global changes, Paleo-Asian Ocean subduction, and continental splicing, which resulted in a continuous increase in terrestrial organic matter, water desalination, and oxidation-rich sediments in the Mosuowan region, but the P–T biological mass extinction event was not recorded.

Sedimentary records of mid-Holocene extreme storm events on the north bank of Hangzhou Bay, East China

Reconstructing the long-term history of tropical cyclones is key to understanding their driving mechanisms and to enable better predictions of future extreme storm events. However, the available history of typhoons, based on sedimentary records in the northwest Pacific basin, remains very limited. In this study, we conducted multi-proxy analyses of sedimentary profiles collected from a chenier ridge on the north bank of Hangzhou Bay, East China. We applied evidences from the lithology, grain size, and marine micro-fossils on sediments in these profiles, dated using OSL and AMS 14C, to reveal the mid-Holocene sedimentary environmental evolution and obtain records of extreme storm events. The lithology and foraminiferal assemblages indicate an aggradational succession from intertidal to supratidal flats incorporating two layers of storm deposits preserved in the chenier ridge. The lower layer of storm deposits was formed in the intertidal flats at ca. 6.0 cal. kyr BP, while the upper layer was formed in the supratidal flats at ca. 5.2–4.9 cal. kyr BP. The storm deposits are characterized by coarsened grain size and the prevalence of allochthonous foraminiferal species, including E. advenum, A. annectens, and A. compressiuscula which occur in the inner and middle shelf of East China Sea. The extreme storm events at ca. 6.0 and 5.2–4.9 cal. kyr BP recorded at the chenier ridge have also been described at different sites on the southeast coast of Hangzhou Bay. Together with previously reported storm deposits at ca. 4.5 cal. kyr BP, we suggest that these mid-Holocene extreme typhoon events on the East China coast resulted from global climate changes driven by solar irradiance.

Late Quaternary sedimentation and neotectonics in Liaodong Bay, northern Bohai Sea

The Bohai Sea is a typical shelf sea, with obvious sediment differences in different regions. Although Liaodong Bay is the largest bay in the Bohai Sea, there lacks boreholes with precise dating. In this paper, the core sediments taken from YKC-2 borehole in the northeastern of Liaodong Bay are dated with AMS14C and OSL, in addition to grain size analysis, foraminifera and pollen identification, lithological characteristics and other testing results. Correlation is made with the global sea level change curve, and upon the basis the evolution of paleoenvironment in the northeast of Liaodong Bay is reconstructed. It is speculated that the age of the bottom of borehole YKC-2 is 150 kyr B.P., and two transgressions have been recorded, similar to the situation in JXC-1, a borehole 46.7 km to the west. It can be found that the sedimentation rate of YKC-2 borehole is obviously higher than that of JXC-1. The authors’ research found that it is mainly controlled by two factors: the provenance difference and the differential movement of basin controlling faults. In the west, sediments are mainly transported by the Bohai Sea current, with insufficient sediment supply, and the basin-controlling faults are rather stable and very weak in activity. In the east, sediments are transported mainly by the surrounding rivers with sufficient sediment supply; and the changes in accommodation space are under the control of the Tan-Lu fault zone. Affected by the strong extensional dynamic environment of the Bohai Bay Basin, the accommodation space, where the borehole YKC-2 is located, continuously increased for deposition of near-source river sediments. This article is an endeavor to study the evolution of the Late Quaternary sedimentary environment and the influence of tectonic activity on Quaternary sedimentation in the Bohai Sea.

Holocene Environmental Evolution Response to the Human Activities and East Asian Summer Monsoon Variation in the Liangzhu Ancient City Complex, Eastern China

The Liangzhu Ancient City Complex is located in a low-lying coastal delta area, and its environmental evolution would have had a significant impact on the human-environment interactions. In this study, element geochemistry and grain size of the sediment sequence from a dam section in Ganggongling (GGL) reveal crucial aspects of sedimentary dynamics, environmental evolution, human activities, and East Asian Summer Monsoon(EASM) variation in the Liangzhu area since 5500 a. Starting from the middle-to-late Holocene, the GGL section shows an overall transition from warm humidity to cold-dry, which is consistent with the climate record dimension in southern China. Through comprehensive analysis of the sedimentary environment before and after the dam’s completion, it can be found that the Ganggongling dam has played a positive role in regulating mountain torrents and met the needs of production and domestic water, such as rice planting through water storage. Further applications on the multi-decadal to centennial time scale demonstrate that variations in solar activity may control the EASM intensity mainly in southern China, which is subject to ENSO intensity changes.

Late Miocene-Quaternary sedimentary environment evolution of the Kerch seep area, Black Sea

A set of 2D high resolution seismic lines was acquired near the Kerch Peninsula during R/V Meteor Cruise M72/3 in March/April 2007 to the Eastern Black Sea. The high resolution seismic data were used for analysis of seismic facies and seismic sequences to gain insight into the sedimentary evolution of the study area. Seven seismic facies types were identified and six seismic units could be mapped. Based on seismic line interpretation, isopach and seismic facies distribution maps, a chronostratigraphic framework could be established for the study area. The study reveals that the sediment deposits were influenced by syndepositional tectonic movements, sea level and climate. During the late Miocene and the early Pliocene, possible slope fan deposits developed. At the boundary between the Miocene and Pliocene, the Messinian erosional truncation surface was observed. After the Messinian sea level fall, accompanied by a major transgressional phase during the Pliocene, the Paleo-Don and Kuban Rivers delivered a large terrigenous input to the Black Sea from the uplifted Crimean Mountains. This formed thick submarine fan deposits near the mouth of Kerch Strait during the late Pliocene. Facies variations within the seismic units are related to the sea-level and climate curves, and are reflected by grain size variations in the sediments and the shift of the river mouth. During the Quaternary, hemipelagic sediments interbedded with coarse-grained fluvial sediments developed in the study area, along with slumps, river channels and fan deposits.