Depositional History Research Articles

U–Pb age constraints on the Carboniferous–Permian transition in continental basins of eastern equatorial Pangaea (France): implications for the depositional history and correlations across the late Variscan Belt

Intramontane late Carboniferous–Permian basins of western Europe developed during the latest orogenic stages of the Variscan Mountain Belt in eastern Pangaea, at equatorial palaeolatitudes. Their stratigraphic framework is mainly based on continental subdivisions (e.g. Stephanian and Autunian continental stages), which can be contentious owing to biostratigraphic biases, resulting in long-distance diachronous subdivisions. To provide precise inter-basinal and global correlations to the internationally recognized chronostratigraphic marine stages, this study reports new U–Pb geochronology from the Aumance and Decize–La Machine basins, located in the northern French Massif Central. Zircon grains extracted from three volcanic ash-fall layers give weighted mean 206 Pb/ 238 U ages of 299.11 ± 0.35, 298.73 ± 0.36 and 298.59 ± 0.35 Ma (2 σ total propagated uncertainty) by the chemical abrasion isotope dilution thermal ionization mass spectrometry method, coinciding with the Carboniferous–Permian transition (Gzhelian and Asselian stages). These ages imply that the northern Massif Central basins developed synchronously in relatively short periods of time (<10 myr), reflecting substantial sedimentation rates. Finally, the new chronology of infilling of these basins confirms that they were connected during the late Carboniferous and early Permian periods, improving the knowledge on the late orogenic Variscan geodynamic setting in this area. Supplementary material: Operating conditions and complete analytical results are available at https://doi.org/10.6084/m9.figshare.c.6805228

Из архива профессора Д. П. Григорьева: к 250-летию Горного музея

The article continues the series on the history of geology and is devoted to the Natural Science Museum of the St. Petersburg Mining University, namely its mineral collection. From the letters found by the author in the archive of Professor D. P. Grigoriev’s
 archive, kept in the Russian Mineralogical Society we can learn, interesting information about the circumstances of the acquisition of certain collections and exhibits, and about people worthy to remain in the history of mineralogy. At the same time, wide connections of D. P. Grigoriev with industrial and academic organisations and his active work on the creation and dissemination of the doctrine of mineral ontogeny, which eventually became a section of the university course of mineralogy, were revealed. The letters were accompanied by photographs from the same archive. The aim of the article was to cover the history of Russian mineralogy as fully as possible, including the role of organisations and individuals, and to reconstruct details of their biographies. Some of the problems discussed in the letters are still relevant today. The reader's attention should be attracted by the names of statesmen Prince G. Orbeliani, Prime Minister of India J. Nehru, Emperor of Ethiopia H. Selassie, mineralogists A. E. Fersman, G. N. Vertushkov, Yu. S. Kobya­shev, name of the Ural historical deposits Gumeshevka and Vatikha, enterprise «Russian precious stones» mentioned in one context. The article is timed to coincide with the 250th anniversary of the Mining Museum.

Textural characteristics and sediment transport dynamics of the sandstones of the Nkporo group, Southern Anambra Basin (Nigeria): evidence for the upper cretaceous sea-level lowstand

The Anambra sedimentary basin is one of the major inland basins in Nigeria. It covers an area of approximately 30,000 square kilometres and is named after the Anambra River, which traverses the basin. The geology of the basin is characterized by a complex sequence of sedimentary rocks that record a long history of deposition and tectonic activity. Detailed and systematic field investigation of its rock sequences exposed at Leru junction and adjoining localities revealed five dominant lithologic units consisting of massive sandstone facies, argillaceous sandstone facies, fissile black shale and mudstone facies, planar and ripple laminated sandstone facies, and massive and pebbly sandstone facies. The area is dominated by transgressive facies characterized by alternating sequences of thinly and parallel laminated fissile black shales, mudstones, and argillaceous sandstones overlain by regressive deposits dominated by massive and partly pebbly sandstones. The transgressive sequences perhaps represented shelf mud sedimentation that was probably interrupted by episodic influxes of sands rich in argillaceous materials transported down the shelf probably by shoreface waves or gravity-driven flows, while the regressive facies may have probably been emplaced by liquefied sand flows of the frontal slope of an advancing mouth bar. The erosion of the shelf deposits by the pebbly sandstones possibly reflected seaward migration of shallow distributary channels during sea-level low stand. Thus, facies transition from argillaceous sandstones to massive and pebbly sandstones within the continental shelf perhaps signified a fall in the relative sea level possibly triggered by the erosion of the shelf or perhaps a high rate of sediment supply.

The eight architectural zones of nonmarine basins

Abstract One of the goals of sequence stratigraphy is to model the conditions that generate stratigraphic architecture at outcrop to basin scales. Accommodation and sedimentation are the principal variables included in sequence-stratigraphic models that describe facies architecture in marine successions. Similar models exist to describe wholly nonmarine architecture. Distinct models are commonly applied to basins containing predominantly lacustrine or predominantly fluvial facies, which can make it difficult to apply models to the entire history of a basin that may include both lacustrine-dominated or fluvial-dominated phases, depending on climatic and tectonic conditions. To account for these changing conditions over the history of nonmarine basins, we present a conceptual three-dimensional model that describes the potential architectural patterns under specific combinations of accommodation, sediment flux, and water balance. Sectors of the model delineate where basins are underfilled or overfilled with respect to accommodation and limited with respect to sediment and water, creating eight zones with different implications for the development of facies architecture. Different types of basins (e.g., foreland, extensional, pull-apart, intracratonic) show broadly different trends in architecture through time. Subtle changes in accommodation, sedimentation, and water balance in the model correspond to shifts in facies architecture between lithostratigraphic units, but architectural transitions within individual basins are more important indicators of evolving basin conditions than comparisons among all basins. This model may serve as a guide for comparing the influence of distinct drivers of architecture among different types of basins as well as identifying important intervals of change during the history of basin filling. The availability of commensurate data on the history of accommodation, sedimentation, and water balance is, however, an ongoing challenge to reconstructing complete basin histories. Future analyses will test how well predicted facies stacking patterns compare to observed nonmarine stratigraphic successions resulting from the combination of accommodation, sediment flux, and water balance during the history of basin filling.

Using sedimentary prokaryotic communities to assess historical changes in the Gippsland Lakes

Abstract The Gippsland Lakes is the largest estuarine system in Australia. Over the last 2 centuries, this unique aquatic ecosystem has suffered substantial modifications mostly associated with anthropogenic impacts, including the creation in 1889 of an artificial channel to the ocean after European arrival, creating chronic salinisation in the system. However, the biological impacts of this historic shift are unclear. Here, we use shotgun metagenomics of environmental DNA from historical sediments of Lake King and Lake Victoria to detect ancient microbial DNA and track past ecological changes in prokaryotic communities. Sedimentary prokaryotic communities changed with core depth, organic matter levels and European arrival. Specifically, we observed an increase in sulfate‐reducing bacteria (e.g., Desulfobacterales) and organic matter enrichment in the upper layers of the sediment cores of the Gippsland Lakes, which could reflect a period of eutrophication caused by higher rates of organic deposition and marine intrusion post‐European arrival. However, while some species presented authentic ancient DNA signals, the shifts in community composition probably reflect changes in indigenous sediment‐dwelling microorganisms in response to geochemical changes of the sediment. Overall, these observations suggest that historic waterway management practices may influence microbial systems today and that sedimentary microbial communities can change in response to both natural biogeochemical dynamics along the depth profile and past environmental conditions.

A Predictive Model For Quantifying The Combined Effect Of Land Use Change And Climatic Variability On Sedimentation In Malaba Sub Catchment

Over the previous years, sedimentation in Malaba sub catchment has become a major problem, this research aimed at using SWAT as a predictive model to assess the impacts of historical and future climate change and land use changes on sedimentation in Malaba sub catchment. Two variables rainfall and temperature were considered under climate change. Four scenarios were modeled in SWAT during this study, the first scenario focused on historical sedimentation in the catchment, land use data of 2000 and weather data of 1990 to 2005 was used to simulate flow and sediment yield in the catchment. The second scenario focused on the current sediment yield in the catchment where land use data of 2020 and weather data of 2003 to 2020 was used to simulate the sediment yield and flow. Calibration and validation was done using SWAT CUP software. The calibrated and validated model was then used to further simulate two future scenarios. The two future scenarios used projected land use data and projected weather data. Land use data was projected using Clerk Labs Terr set software while weather data was projected using the Statistical Downscaling Model (SDSM). The third scenario considered projected land use data of 2035 and projected weather data of 2020 to 2035 to simulate flow and sediment yield of 2023 to 2035. The forth scenario considered projected land use data of 2050 and projected weather data of 2033 to 2050 to simulate catchment flow and sediment yield of 2036 to 2050. The results obtained from climate change analysis indicated un even changes, rainfall over the catchment is expected to increase, maximum temperature is expected to increase, minimum temperature is expected to reduce. Land use change results after comparison between the historical land use and projected land use indicated that from 2020 to 2050 cropland and built up area will increase while forests and water bodies will reduce. Average annual Sediment yield of 1993 to 2020 is expected to generally increase from 4975.4 tons/km2/year to an average annual sediment yield of 5525.6 tons/km2/year from 2023 to 2050. Therefore, mitigation measures should be adopted to ensure sustainable management of the catchment. Some of the recommendations made in this research are; Government through NEMA should put restrictions on cultivation close to the river banks, encourage planting trees within the catchment, bare lands within the catchment should be converted to other sustainable land uses. The study findings of this research shall be relevant for planning, design and management of reservoirs, dams, irrigation systems and sustainability of eco systems in the catchment.

A century-long record of polycyclic aromatic hydrocarbon deposition in the Old Yellow River Estuary, China

Polycyclic aromatic hydrocarbons (PAHs) are potential geochemical indicators for assessing the impact of human activities and can be used to reconstruct historical human activities. This study collected a 108 cm sediment core from the 5th lobe of the Yellow River Delta for the first time and analyzed the historical distribution characteristics of PAHs in this area. The results showed that the sedimentation history of the core was from 1908 to 2014. The average value of PAHs was 28.93 ng/g. Biomass and coal combustion sources were the main sources of PAHs in the low-value areas, while oil spill sources were the main sources in the significantly higher PAHs areas in the 1960s, mid-1980s, late 1990s, and late 2010s, which was consistent with the development history of Shengli Oilfield. Compared with global estuaries, the historical industrial activity intensity in this area was weaker.

Rapid laminated clastic alluviation associated with increased Little Ice Age flooding co-driven by climate variability and historic land-use in the middle Severn catchment, UK

The analysis of exceptionally well-preserved visible clastic laminations in deep alluvial sediments at Kempsey, Worcestershire (UK), allows a new high-resolution analysis of late-Holocene flood-history in the largest UK catchment, as well as local human response. At the sample site over 4.5 m of sandy-silt overbank-alluvium accumulated on the floodplain and optically stimulated luminescence (OSL) dating of the upper 2.25 m demonstrates accretion from the late 14th century CE onwards. Sub-centimetre to centimetre resolution multi-proxy sediment analysis (loss on ignition, magnetic susceptibility, particle size, ITRAX and portable XRF) demonstrate clear variations in depositional history over the last millennium due to channel stability. Between c. 1380 and 1550 CE overbank sedimentation was driven by lower energy flood events, with negligible effect from climatic conditions during the Spörer Minimum (1460–1550 CE). After c. 1550 CE the magnitude of flooding events increased and by c. 1610 CE, the start of the visible sub-centimetre laminations, the accumulation rate regularly exceeded 3 mm year−1, which increased to 4.5 mm year−1 between c. 1690 and 1710 CE, and 3 and 3.5 mm year−1 between c. 1790 and 1840 CE before alluviation was altered by an embankment. The greatest extent of coarse overbank deposition and increased accumulation rate occur concurrently with periods of climatic instability associated with the Maunder (1645–1715 CE) and Dalton (1790–1820 CE) Minima, the periods of largest historical floods and during the intensification of arable cultivation across the middle Severn catchment. This data correlates well with other sites in the catchment suggesting that these are basin-wide forcing-responses. We also present evidence that this catchment-wide hydro-geomorphological history had local effects in shifting the geographical focus of an important settlement away from its historic floodplain edge location – which can be viewed as an adaptation to the flood risk.

Integrated biostratigraphy and chemostratigraphy of the Maastrichtian–Danian succession at Abu Minqar, Egyptian Western Desert: Implications for sequence stratigraphy and tectonic influence

We investigated the Maastrichtian–Danian succession at the Abu Minqar section in the Western Desert of Egypt (part from the southern Tethyan margin) using an integrated analysis of biostratigraphic (calcareous nannofossils, foraminifers, macrofauna) and chemostratigraphic data to determine the controlling factors on depositional history. The integrated microplankton biostratigraphic framework identified two prolonged hiatuses at the lower/upper Maastrichtian and the Maastrichtian/Danian boundaries. Four depositional sequences were identified and subdivided into systems tracts based on paleodepth variation evidenced by foraminiferal investigations and the comparable response of the various geochemical indices. The study also highlighted the presence of two alternated depositional styles in the study area, influenced by relative sea level, with the first style involving the deposition of aluminosilicate-enriched intervals that yield non-calcareous foraminifers in lagoonal and coastal depositional settings induced by relative sea-level fall and river rejuvenation, and the second one involving the deposition of calcareous intervals containing abundant megafossils, calcareous foraminifers, and nannofossils during a sea-level rise. Despite the occurrence of certain resemblances to the global eustatic curves, the inferred relative sea level pattern suggests that regional tectonics had a substantial role in developing the depositional history and paleoenvironmental circumstances of the southern Tethys margin. These findings help build a more comprehensive picture of the geological evolution of the southern Tethyan margin during the Late Cretaceous to Paleogene.

Early Mesozoic accretionary complex scattered throughout NE China and its tectonic implications: Insights from the mylonitic meta-sedimentary rocks in Huanan, Heilongjiang Province

In NE Asia, the early stage (T-J) subduction history of the Paleo-Pacific oceanic plate was largely reconstructed by studies on the Heilongjiang complex, a blueschist-containing N-S trending high-pressure metamorphic belt, which is suggested to represent the “suture zone” between the Jiamusi Block and the rest of the Central Asian Orogenic Belt. However, recently more accretionary complexes with similar geochronological data were reported on both sides of the “suture zone”, making the tectonic affinities of the “suture zone” unclear. Here, we select the mylonitic meta-sedimentary rocks in Huanan, one of the potential accretionary complexes near the central Jiamusi Block to reveal its depositional and metamorphic history and discuss the tectonic implications. Our results show that these rocks were deposited in/after the Late Triassic (defined by the youngest detrital zircon group) and accepted clastics from both the Jiamusi and Songliao blocks. Before the Early Jurassic (c. 178 Ma by apatite UPb dating results in this study), they experienced high-P/low-T metamorphism (510–520 °C and 10.5–11 kbar), and then were heated to about 610 °C at 8.5–9.2 kbar during exhumation. The meta-sedimentary rocks in Huanan are components of the early Mesozoic accretionary complex in NE China. However, their present location is c. 85 km to the east of the previous proposed “suture zone” from Luobei to Mudanjiang. Considering the spatially scattering distribution of other similar accretionary complexes, such as the Zhangguangcai complex (c. 40 km to the west of the “suture zone”), we suggest that these complexes dispersedly exposed throughout NE China were either nappes transported by post-exhumation thrusting, or remnants of archipelagic oceanic crusts in the NW Paleo-Pacific region during the early Mesozoic.

CLADOCERA COMMUNITIES OF LAKE ARCTO-PIMBERTO (NENETS AUTONOMOUS DISTRICT) IN THE MIDDLE AND LATE HOLOCENE<a href="#FN1"><sup>1</sup></a>

The analysis of the subfossil Cladocera community in the bottom sediments from Lake Arcto-Pimberto located in the Pechora River delta (Nenets Autonomous District) was carried out. A 95-cm-long continuous core of bottom sediments was collected in the deepest part of the lake and covers approximately 6400 years of sediment accumulation during Middle and Late Holocene. 17 cladoceran taxa were identified in the studied core. Species with Holarctic and Palearctic distributions prevailed in the lake. Most of the identified subfossil remains belong to pelagic species living in the open part of the lake. Found fragments of chitinized remains of Rhynchotalona falcata and Alonopsis elongata indicate the presence of sandy soils in the water body. The samples were dominated by Bosmina (Eubosmina) longispina and Chydorus cf. sphaericus, which are evenly distributed along the continuous sediment core. We have studied the history of the development and evolution of the lake based on changing of the taxonomic composition of microcrustaceans in the bottom sediment core. The structure of the subfossil Cladocera community stayed relatively constant. The ratio of pelagic and littoral-phytophilic taxa changed slightly. Depending on the changes in the species composition of the cladoceran assemblage, the sediment core was divided into 4 ecological zones. In the early history of sedimentation in the lake, there is a small peak in the abundance of crustaceans, followed by decrease and further gradual increase towards the upper horizons of the column. Between from 5700 cal. years BP to 2100 cal. years BP there is an increase in abundance of pelagic organisms, with a decrease in abundance of littoral taxa. This marks the presence of a well-developed pelagic part of the reservoir at that time. In the upper zones, we observe the taxonomic diversity of littoral organisms and an increase in abundance of their remains. The Shannon-Weaver species diversity Index showed a simple organization of the community of subfossil Cladocera. The Pantle and Buck saprobity Index characterized the lake as oligosaprobic, this status is maintained throughout its evolution of the lake.

Geophysical and geological exploration of the Aurus clay pan as an archive of the long-term climatic and environmental history of the Namib Desert

The Namib Desert is one of the oldest deserts on Earth. Whilst the history of the desert during the last glacial-interglacial cycle is relatively well understood, information on the older Pleistocene and Neogene history is very scarce, because longer-term records such as those in lakes and caves have not been formed due to the aridity. Here, we investigate the potential of the sedimentary record in the Aurus clay pan in the Sperrgebiet Domain in the southern Namib Desert, Namibia, for longer-term paleoclimate research. For this purpose, we conducted a multi-disciplinary geophysical site survey along with initial sedimentological investigations. We used a combination of transient electromagnetic (TEM), seismic and magnetic data, that allows us to derive information with respect to tectonic features as well as the deeper sedimentary architecture of the Aurus clay pan. TEM and seismics were applied along two perpendicular transects. The data obtained reveal a three- to four-layered subsurface structure with a maximum sedimentary thickness between 31 and 65 m overlaying resistive bedrock. The aeromagnetic data show a fault zone cutting the southwestern corner of the clay pan that correlates with deep conductive anomalies visible in the TEM data. Radiocarbon ages of plant remains from the sediment surface evidence modern deflation, probably due to a particularly dry climate. The composition of a 4-m-long sediment core, which probably reflects the depositional history from 3400 to 23,000 cal. yr BP, however, suggests that most of the Holocene was characterized by a relatively high humidity, whereas the latest Pleistocene again was much dryer. According to an extrapolation of the sedimentation rates in the upper 4 m to the base of the sedimentary infill the record in Aurus clay pan penetrates in the order of 340,000 cal. yr BP. This would be longer than most other paleoclimate records in the Namib, but much less then recently recovered in the Atacama Desert in Chile. A comparison of the geophysical and geological data from Aurus with comparable data and two drill cores from clay pans in the Atacama furthermore shows that the physical parameter in all cases allow to decipher the sediment thickness and general architecture, but alone provides limited information on the sediment composition.

In front of the retreating ice-sheet: Fauna complex of central-western Poland in MIS 3–2 (Krosinko site)

A new locality in Central Europe (Krosinko, Poland) yields a rich fossil material of great taxonomical variety. Its location in the Warsaw–Berlin ice-marginal valley, where it forms a 1-m horizon at a the depth of 6–8 m, is suited to a taphonomic analysis aimed at reconstructing the paleoevents and depositional history of the late Pleistocene (MIS 3–2).Our analysis revealed that the material accumulated as the result of high-energy fluvial transport. This transport disturbed the original bone associations, as indicated by the lack of articulation, low refitting, and bone surface modification. During water movement, the bones were polished, abraded, pitted, and fragmented. Prior to that, however, taphonomic signatures were left behind by predators, humans, and plant roots. This is the first time that unquestionable burning marks have been found on woolly rhino remains from Poland.The secondary context of the faunal assemblage was confirmed by neodymium isotope studies of the faunal fragments and sediment. Given the results of sedimentological analysis from previous studies, these sediments can be associated with a high-energy braided river. The remains were moved along with paleobotanical material and flints in a westerly direction; this is suggested by the direction of water flows in the valley and the river waters supplying it.The deposition occurred within a single geologic event around 26 ka BP, as indicated by the youngest radiocarbon date of the remains, or ca. 19 ka BP, considering the geochronological constraints for the local LGM ice margin position in central and eastern Poland ∼22–18 ka, and the specified accumulation time of the sediments in which they were found. Secondary mineralization of manganese and iron on the bones was the final taphonomical process that impacted the remains.The combined taphonomic, palaeozoological, isotopic and geological results show for the first time for a Polish paleontological site how data integration improves interpretation and highlights the advantages of a multiproxy approach.

Geochemistry and petrology of the Chandarpur-Raipur sandstones: Implications for the evolution of the Chattisgarh Basin, Central India

Depositional processes and stratigraphic evolution of the Chattisgarh basin exhibit a synergistic relation between sedimentation and tectonics. To interpret the sedimentation history and basin evolution, multiproxy approach including field studies, petrography, geochemical, and multivariate statistical analyses of the sandstones of Chandarpur and Raipur groups is employed. The study provides a detailed analysis of the time-connoted petrography and geochemistry of the sandstone units from each formation of the Chandarpur-Raipur sequence of Chattisgarh basin. The sandstones grade from immature wacke through submature arkose to mature quartzarenite from the bottom up the section. These sandstones are broadly characterized by felsic provenance, arid-humid palaeoclimate, and weak-intense palaeoweathering at the source. The assemblage of wacke-arkose-sublitharenite of the basal Lohardih Formation is characteristics of fan delta environment and represents initiation of rifting and basin formation stage. Subarkoses from the younging up sequence of Lohardih-Chaporadih-Kansapathar formations reflect prograding shelf environment that represents craton interior field of the continental block provenance and passive marginal tectonic setting, indicating gradual stabilization of the basin. Quartzarenites from Kansapathar Formation and stratigraphically younger Devsagar Member of Charmuria Formation also represent broadly similar provenance and tectonic setting indicating stable craton interior provenance in a passive marginal setting. Petrographic and geochemical analyses of some of the Kansapathar-Devsagar sandstones suggesting recycled orogen provenance, however, may be attributed to the orogenic activity and/or role of younger bimodal volcanic rock during rejuvenation of multistage basin opening faults. Rifting stage was followed by subsidence stage as indicated by the presence of black limestone capping the sandstone successions. Initiation of basin formation ∼1400 Ma and sedimentation can be correlated with the late-stage fragmentation of the supercontinent Columbia. The basin probably closed ∼1000 Ma during the assembly of the next supercontinent Rodinia. It is estimated that ∼87% of the 2.2-km-thick sedimentary succession in the eastern Chattisgarh basin, were already deposited within this time frame (∼1405 and ∼1007 Ma). The basin is correlatable with other Mesoproterozoic basins of Peninsular India like Vindhyan, Cuddapah basins, as well as with basins like Xiong’er rift basin of North China Craton, Espinhaco basin of eastern Brazil, that are related to the Columbia-Rodinia Supercontinent cycle.

Distribution of organochlorine pesticides (OCPs) in surface-mixed layer water and intertidal sediments of Lagos lagoon, Gulf of Guinea

Organochlorinated pesticides (OCPs) were analysed in intertidal sediments and surface-mixed layer water of Lagos lagoon in Nigeria in order to elucidate the contamination levels, sources and distribution characteristics, and potential human and ecological health risks associated with exposures to OCPs. The total ∑ OCPs in sediments ranged from 222.35 to 2585.30 μg/kg dw, with a mean concentration range between 13.08 and 172.35 μg/kg dw, respectively. The most dominant OCP compounds in the sediments were dichlorodiphenylethanes (40%), chlors (26%), cyclodienes (17%), HCHs (9%), and endos (8%). The concentration (μg/kg) of individual ∑OCP groups in sediment decreased in the following order: ∑ dichlorodiphenylethanes > ∑ Chlors > ∑ Cyclodienes > ∑ HCHs > ∑ Endos. The ∑ OCPs in water ranged from 23.63 (mean concentration: 1.97 ng/L) to 172.05 ng/L (mean concentration: 13.23 ng/L). Dichlorodiphenylethanes (46%), cyclodienes (21%), chlors (14%), HCHs (12%), and endos (7%) were the most prevalent OCP compounds in investigated water samples. These locations are pollution hotspots for potential wastes arising from industrial effluents, heavy shipping activities, municipal wastes and discharges of transformer oil from abandoned power generation and transmission facilities. The total composition and β-, γ- and δ-HCH isomeric ratios suggest recent anthropogenic introduction of the HCHs into the lagoonal ecosystem compared to historical deposits. Dichlorodiphenylethanes (p,p′-DDD, p,p′-DDE, and methoxychlor) were ubiquitous except p,p′-DDT. Results indicate historical inputs of technical DDT with considerable biodegradation and photochemical transformations. Generally, the ∑ chlors in sediments and surface-mixed layer water samples decreased following heptachlor > heptachlor epoxide > α-Chlordane > γ-Chlordane. The α-chlordane/γ-chlordane ratios indicate a mix of recent commercial and historical chlordane contamination sources. Concentrations of most OCPs significantly exceeded sediment quality guidelines suggesting that toxicity to benthic-dwelling faunas is estimated to be likely.

Centennial-scale source shift in potentially toxic metal(loid)s in Yangtze River

Estuarine sedimentation is an important historical record of potentially toxic metal (PTM) emissions from human activities that can be used to improve environmental management. However, the contribution of different human activities to PTM deposition has not been accurately estimated, and their coupled relationship with riverine organic matter is typically not considered. In this study, we reconstruct the century-scale PTM depositional history of sediment cores from the Yangtze Grand Delta. Eight potential metal sources (PMSs) were identified using positive matrix factorization, and the results of lagged correlation determined the PMSs associated with the riverine discharge of the Yangtze River. Riverine PTMs were predominantly composed of Cr (79.0%), Ni (77.3%), and Pb (64.1%) but were deprived in Cu (34.9%). Glomalin-related soil protein (GRSP), which is a typical terrestrial refractory carbon, has a strong affinity for Cu, and contributed to 2.82–22.6% Cu deposition. The change in the PMS is mainly related to power generation, whereas the GRSP-bound PTM is mainly related to road construction and transportation. We advocate for responsible management of human activities in river catchments, particularly on coal-based power generation and road transportation, to maintain ecological security and promote the overall achievement of the Sustainable Development Goals.

Integrated geological data, 3D post‐stack seismic inversion, depositional modelling and geostatistical modelling towards a better prediction of reservoir property distribution for near‐field exploration: A case study from the eastern Sirt Basin, Libya

De‐risking the hydrocarbon potential in near‐field exploration is one of the most important procedures in the exploration of hydrocarbons, and it requires the integration of various data to predict the reservoir characteristics of the prospect area more accurately. In this work, wells and 3D seismic data from the Libyan producing oil fields were utilized to demonstrate how well this technique worked to improve and describe the hydrocarbon potential of the carbonate geobody that corresponds to the Palaeocene Upper Sabil Formation, which was revealed by new seismic data. This study integrates different types of data, including 3D seismic, seismic acoustic impedance, depositional history and geostatistical analysis, to predict the facies, reservoir porosity and permeability distributions and then visualize them in a 3D reservoir model. The 3D seismic data analysis revealed the presence of a clear seismic anomaly geobody (GB) that has never been penetrated by any well. The sedimentological analysis for the well adjacent to the GB indicated a deep‐water depositional environment as turbidites surrounded by deep‐water mud dominated facies. The Upper Palaeocene interval in the study area was subdivided based on the depositional facies and seismic stratigraphy into eight zones that were used to build the reservoir model framework. According to the porosity permeability relationships, the carbonate facies has been classified into five E‐Facies, that is, soft highly argillaceous limestone, hard argillaceous limestone, porous limestone (<20% porosity, and >30% shale volume), medium quality limestone (10–20% porosity, and >30% shale volume) and tight limestone (<10% porosity, and >30% shale volume). The rock physics and inversion feasibility analysis indicated that the acoustic impedance (AI) can be used to predict the porosity but not the lithology or the fluid content. The Bayesian classification has shown excellent results in predicting and modelling the reservoir facies distribution within the study area, utilizing the integration of gross depositional maps (GDEs), wells and seismic data. The reservoir quality of the GB was predicted by using the post‐stack seismic inversion, which indicated a high porosity interval (25%–30%). Moreover, the statistical analysis integrated with the well and seismic data was used to predict the GB permeability. The predicted permeability was reasonably high (40–60 mD). The final E‐facies show an excellent match with the input well data and an excellent match with the blind wells that were used for result quality control (QC) with higher vertical resolution. The developed model can be used as a guide for de‐risking the studied GB hydrocarbon potential in the studied basin, and it can be applied in other similar geological conditions worldwide for exploring underexplored reservoirs and de‐risking their hydrocarbon potential.

Pre-salt carbonate cyclicity and depositional environment: NMR petrophysics and Markov cyclicity of lacustrine acoustic facies (Santos Basin, Brazil)

The Pre-salt strata are idealized as a lake-dominated breakup depositional sequence recorded between the South American and African continental margins to which there is no present-day analog. Most of the complexities of the Pre-salt reservoir rely on addressing carbonate cyclicities at different scales using limited cored intervals where well-log and seismic correlation is still unclear. In this case, the application of borehole image logs (BHI) and nuclear magnetic resonance (NMR) techniques allows not only the scale correlation and extensive data acquisition but also to establish a more robust relationship between acoustic facies and their petrophysical significance. For that, this work combines BHI and NMR data to propose a feasible scheme of depositional acoustic facies for the Barra Velha Formation in the Santos Basin. To verify the statistical significance of the acoustic facies’ vertical organization, this work applied the Markov chain analysis along a c. 500 m stratigraphic interval, deriving four carbonate cycles associated with shallowing and reworking lacustrine cyclicities. Abrupt changes in cyclicity patterns were adopted as stratigraphic markers to subdivide the succession into lowermost, intermediate, and uppermost intervals that record the depositional history of deep, shallow, and emergent lake environments, respectively. By comparing the thickness variation of the Markovian cycles (i.e., accommodation space) with the seismic onlap curve variation (i.e., lake level) throughout the Pre-salt interval, a larger-scale superimposed cycle was unraveled, suggesting that accommodation space of the studied Pre-salt paleolake was likely controlled by fluctuations in the lake level. Finally, this work aimed to explore the applicability of diagnostic criteria for the description and interpretation of depositional acoustic facies, their petrophysical significance, and cyclicity patterns in the Barra Velha Formation.

Biological carbon pump responses to multiscale physical processes: a review of sediment trap studies in the South China Sea

Accurately assessing the capacity of the modern ocean to photosynthetically fix and sequester atmospheric CO2, termed the biological carbon pump (BCP), is a key component in studies on the marine carbon cycle and the global climate system. Particulate organic carbon (POC) flux into the ocean interior is an important indicator of the BCP strength, and it can be directly measured by sediment traps on time scales from days to years. This study has been conducted in the South China Sea (SCS) for over three decades. The SCS is one of the largest tropical marginal seas, located in the Asian monsoon region with frequent occurrence of dynamic physical processes and anthropogenic perturbations. It hosts an ideal natural laboratory to investigate the response of the BCP to multiscale physical processes. In this mini review, we briefly introduce the study history of mooring sediment traps in the SCS, synthesize the processes that regulate the temporal variability in mesopelagic POC flux, and how it is sensitive to climate changes. The time-series characteristics of the POC flux are clearly linked to primary production, as well as the key physical processes in the upper layer. The seasonal East Asian monsoon, intraseasonal eddies, aerosol deposition and interannual El Niño Southern Oscillation (ENSO) events are the main controlling factors over weekly to yearly timescales. Together, they suggest that the multiscale physical forcing in the upper layer regulates the mesopelagic POC export flux by controlling nutrient supplementation and subsequent POC production.

Stratigraphy of the middle Triassic-lower Cretaceous succession in the Paraná and Uruguayan Chaco-Paraná Basins – An overview based on subsurface data

The Middle Triassic to Lower Cretaceous (MTLC) megasequence of the Paraná and Uruguayan Chaco-Paraná basins records a complex depositional history. It encompasses a dynamic interplay of continental lacustrine, fluvial, and aeolian sediments that have evolved under varying paleoenvironmental and climatic conditions, ranging from humid to arid and hyper-arid settings. The present subsurface study depicts a novel stratigraphic framework for the MTLC megasequence, drawing from an extensive dataset of over 400 well logs and drilling reports derived from exploratory petroleum and water wells distributed across these basins. The lithostratigraphic units within the MTLC megasequence, as delineated from the well logs, exhibit a consistent stacking pattern with well-defined hierarchic arrangement, which extends throughout the Paraná and Chaco-Paraná basins. Within the MTLC megasequence, three distinct sedimentary successions have been established, bounded by regional unconformities: the Middle to Upper Triassic sequence, the Upper Jurassic sequence, and the Lower Cretaceous sequence. The Middle to Upper Triassic sequence encompasses the Santa Maria/Caturrita, Piramboia, and Itacumbú formations. The Santa Maria/Caturrita sequence extends into the subsurface to Uruguay, where it is referred to as the Itacumbú Formation. The Piramboia Formation has been subdivided into two distinct units: the lower unit retains the name Piramboia Formation, while the upper unit has been designated as the Guará Formation, as it was originally defined in the Rio Grande do Sul State. The Upper Jurassic sequence encompasses the Guará and Tacuarembó formations, extending throughout the entire Paraná and Uruguayan Chaco-Paraná basins. The Lower Cretaceous sequence comprises the Botucatu and Rivera formations. These deposits are generally discontinuous and frequently intercalated with the volcanic rocks of the Serra Geral Formation.