Depositional History Research Articles

Palaeoenvironment and bio-events of the Cretaceous sediments of the Cauvery Basin, India

The Cauvery Basin is an important rift margin basin on the east coast of India. Its long research history began in the mid-nineteenth century with the pioneering work of H. F. Blanford. While much of the Cretaceous succession in the basin is fault-controlled, some of the recorded events represent global sea level changes, especially in the mid-Cretaceous. Macrofossils (ammonites, bivalves, etc.) and foraminifera are abundant throughout, and there is an important occurrence of fossil wood and ‘log-grounds’ in the Turonian–Coniacian. The basin is subdivided into a series of sub-basins (known as depressions in earlier literature), which, in places, have their own distinctive depositional history. The results of our collective fieldwork have provided a re-assessment of the lithostratigraphy, biostratigraphy and the tectono-stratigraphical history of the Ariyalur outcrop. Three sedimentary units have been identified: the syn-rift Gondwana Group (of early Cretaceous age), the syn-rift Uttatur Group (of Albian to Coniacian age) and the post-rift Ariyalur Group (of Santonian to Maastrichtian age). Both microfossil and macrofaunal information have been integrated in order to construct a biostratigraphical framework for the basin and develop a tectono-stratigraphical model. Structures exposed onshore, which have occasionally been interpreted as Albian reefs, are thought to be irregularly shaped limestone olistoliths and olistostromes produced by significant intra-Cretaceous faulting and slumping within the basin.

Anthropogenic and climatic impacts on historic sediment, carbon, and phosphorus accumulation rates using 210Pbex and 137Cs in a sub-watershed linked to Zarivar Lake, Iran

To estimate a watershed’s response to climate change, it is crucial to understand how human activities and climatic extremes have interacted over time. Over the last century, the Zarivar Lake watershed, Iran, has been subjected to various anthropogenic activates, including deforestation and inappropriate land-management practices alongside the implementation of conservation measures like check dams. To understand the effects of these changes on the magnitude of sediment, organic carbon (OC), and phosphorus supplies in a small sub-watershed connected to the lake over the last century, a lake sediment core was dated using 210Pbex and 137Cs as geochronometers. The average mass accumulation rate (MAR), organic carbon accumulation rates (OCAR), and particulate phosphorus accumulation rates (PPAR) of the sediment core were determined to be 6498 ± 2475, 205 ± 85, and 8.9 ± 3.3 g m−2 year−1, respectively. Between the late 1970s and early 1980s, accumulation rates were significantly higher than their averages at 7940 ± 3120, 220 ± 60, and 12.0 ± 2.8 g m−2 year−1 respectively. During this period, the watershed underwent extensive deforestation (12%) on steep slopes, coinciding with higher mean annual precipitations (more than double). Conversely, after 2009, when check dams were installed in the sub-watershed, the sediment load to the lake became negligible. The results of this research indicate that anthropogenic activities had a pronounced effect on MAR, OCAR, and PPAR, causing them to fluctuate from negligible amounts to values twice the averages over the last century, amplified by climatic factors. These results imply that implementing climate-smart watershed management strategies, such as constructing additional check dams and terraces, reinforcing restrictions on deforestation, and minimum tillage practices, can facilitate protection of lacustrine ecosystems under accelerating climate change conditions.Graphical

Integrated Sequence Stratigraphic and Seismic Facies Analysis for Hydrocarbon Prospectivity of the Taranaki Basin, New Zealand

This study analyses the hydrocarbon potential and basin characteristics of the Taranaki Basin in New Zealand, the country's primary petroleum-producing region. The research, which uses a robust methodology involving 2D seismic data, well logs, and other geological information, examines the basin's stratigraphy, structural features, and petroleum systems. Key findings include the identification of two genetic sequences with associated system tracts, multiple reservoir and source rock units, and both structural and stratigraphic trapping mechanisms. Seismic facies analysis revealed eight distinct facies types which characterize the depositional environments. Play fairway mapping identified sweet spots where all petroleum system elements overlap. Risk assessment highlighted factors like gas chimneys and fault-compromised seals. The study concludes by presenting the geologic chance of success for three identified plays and one prospect in different stratigraphic intervals. This comprehensive analysis provides new insights into the under-explored portions of the Taranaki Basin and its hydrocarbon potential. By enhancing the understanding of the basin's stratigraphic architecture and depositional history, this study aims to improve reservoir distribution and quality predictability. Moreover, integrating seismic facies analysis with sequence stratigraphy offers a robust tool for delineating potential hydrocarbon-bearing zones, thereby reducing exploration risk and aiding the efficient reassessment of existing prospective zones and future exploration efforts.

Depositional, stratigraphic and structural controls on the geometry of Montney Formation reservoirs: Lower Triassic, northeast British Columbia, northwest Alberta

Abstract The Lower Triassic Montney Formation is a world-class unconventional hydrocarbon reservoir that spans the border of northeast British Columbia and northwest Alberta. Integrated sedimentological and ichnological analyses suggest that the Montney Formation was deposited in a predominantly prodeltaic setting that was commonly influenced by both river flood and storm processes. Riverine processes include the local occurrence of normally- and inversely-graded siltstone and sandstone interbeds, interpreted as the record of sediment-laden hyperpycnal flows. Episodic storms are recorded by the local occurrence of hummocky cross-stratified interbeds, as well as normally graded, parallel and wave-ripple laminated beds, which are commonly draped by structureless carbonaceous mudstones. These mudstone drapes represent river-flood-derived fluid muds that collapsed from hypopycnal plumes following the passage of the storms and suggest the intimate linkage between storms and heightened fluvial discharge. The basin in which the Montney Formation was deposited began as three sub-basins, northern, central and southern, each of which experienced different patterns of subsidence and uplift that varied both spatially and temporally during sedimentation. Subsidence of the northern sub-basin was compartmentalized by deep seated faults that provided accommodation for the basal sequence of the Montney Formation, Sequence 1. Subsequent fault movement resulted in reduced accommodation in the northern sub-basin and accelerated subsidence in the central sub-basin, providing accommodation for deposition of Sequence 2, the basal sequence in the central sub-basin. The northern sub-basin remained paleotopographically elevated throughout deposition of Sequence 2 and early Sequence 3 successions, and these younger units did not extend beyond the northern limit of the central sub-basin. During subsequent deposition of the late Sequences 3 and Sequence 4 successions, compartmentalization between the north and central sub-basin was greatly reduced and these intervals were deposited relatively more uniformly along-strike. The unconventional and conventional reservoirs in both the northern and central sub-basins occur at the scale of systems tracts within the four depositional sequences of the Montney Formation. Reconstructing the depositional history of the component systems tracts of Sequence 1 through early Sequence 3 reveals the dynamic interplay between syndepositional tectonism, fluctuating relative sea-level and deltaic depositional processes in controlling the character, geometry and distribution of prolific Montney Formation reservoirs. The recognition of these key geological controls enhances predictability in this valuable resource and may be applicable to other fine-grained reservoirs elsewhere.

An Etymological and Controversial Examination of Sun Wukong in <i>Journey to the West</i>

Since the debate between Lu Xun's "indigenous theory" and Hu Shi's "exotic theory" on the origin of the image of Sun Wukong, there has been nearly a hundred years of academic discussion. Scholars from various schools have conducted a large number of beneficial studies and reached well-founded conclusions. However, due to the unique nature of Journey to the West as a work that has been accumulated across generations and carries a distinct historical sediment, the controversy surrounding it has always been at an impasse, with no consensus reached. Based on previous studies, this paper will provide an overview of the mainstream theories within the academic community. It will then conduct etymological and dialectical analysis of the character of Sun Wukong from the perspective of the "indigenous theory", thus demonstrating the high plausibility of the indigenous viewpoint.

Post-glacial stratigraphy and late Holocene record of great Cascadia earthquakes in Ozette Lake, Washington, USA

Ozette Lake is an ~100-m-deep coastal lake located along the outer coast of the Olympic Peninsula (Washington, USA); it is situated above the locked portion of the northern Cascadia megathrust but also relatively isolated from active crustal faults and intraslab earthquakes. Here we present a suite of geophysical and geological evidence for earthquake-triggered mass transport deposits (MTDs) and related turbidite deposition in Ozette Lake since ca. 14 ka. Comprehensive high-resolution bathymetry data, seismic reflection profiles, and sediment cores are used to characterize the post-glacial stratigraphic framework and examine paleoseismic evidence in the lacustrine sediments. Stacked sequences of MTDs along the steep eastern flanks of the lake appear to grade basin-ward from thick, chaotic, blocky masses to thin, parallel-bedded turbidite beds. The discrete turbidite event layers are separated by fine-grained (silt and clay) lake sedimentation. The event layers are observed throughout the lake, but the physical characteristics of the deposits vary considerably depending on proximity to primary depocenters, steep slopes, and subaqueous deltas. A total of 30–34 event deposits are observed in the post-glacial record. Radiometric dating was used to reconstruct a detailed sedimentation history over the last ~5.5 k.y., develop an age model, and estimate the recurrence (365–405 yr) for the most recent 12 event layers. Based on sedimentological characteristics, temporal overlap with other regional paleoseismic chronologies, and recurrence estimates, at least 10 of the dated event layers appear to be sourced from slope failures triggered by intense shaking during megathrust ruptures; the recurrence interval for these 10 events is 440–560 yr. Thus, Ozette Lake contains one of the longest and most robust geological records of repeated shaking along the northern Cascadia subduction zone.

Geochemistry and U–Pb geochronology of detrital zircon grains in beach sediments from the northwestern gulf of Mexico, Tamaulipas, Mexico: Implication for provenance

The mineralogy, bulk geochemical composition, chemistry and U–Pb ages of detrital zircons in sediments from the La Pesca (LP) and Tesoro Altamira (TA) beaches, NW Gulf of Mexico are analyzed. The aim of this study is to infer the weathering history and provenance of sediments, and to identify the potential source terranes that are contributing sediments to the LP and TA beach areas. The beach sediments are rich in quartz and aluminosilicates. The Chemical Index of Weathering (CIW') and trace elements such as Th, Sr, U, and Ba reveal high weathering intensity for the LP and TA beach sediments. Major-element based diagrams and trace elemental ratios based on Co, Cr, Sc, La, and Th contents in sediments indicate felsic provenance, which is further supported by a negative europium anomaly and rare earth element (REE) patterns. The Th/U ratios (>0.3) together with positive cerium and negative europium anomalies of zircons in the LP and TA beaches indicate igneous origin. The comparison of zircon U–Pb ages of this study with ages reported from the adjacent terranes revealed that the Proterozoic (Paleoproterozoic: 1607.07–1943.45 Ma and Mesoproterozoic: 1021.19–1586.52 Ma) zircons are derived from the Oaxaquia, Mesa Central, Sierra Madre Oriental Provinces of Mexico and Mazatzal–Yavapai Province of the USA. On the other hand, Mesozoic (Jurassic 146.49–199.43 Ma and Cretaceous 68.46–136.82 Ma) and Cenozoic (Eocene 33.97–51.46 Ma and Oligocene 23.39–33.86 Ma) zircons are contributed by the Mexican volcanic rocks, Mesa Central and Sierra Madre Oriental Provinces in Mexico, and Mogollon-Datil Volcanic field and Colorado Plateau in USA. The rivers and their tributaries draining from the source areas are considered as a carrier and agent of distributing sediments along the northwestern Gulf of Mexico coastal areas, which are subsequently mixed by littoral currents.

Sedimentary provenance of the Upper Devonian Old Red Sandstone of southern Ireland: an integrated multi-proxy detrital geochronology study

The Devonian Old Red Sandstone (ORS) magnafacies of southern Ireland is hosted in the Early Devonian Dingle Basin and the Late Devonian Munster Basin. Following the closure of the Iapetus Ocean during the Caledonian Orogeny, the Dingle Basin developed as a pull-apart structure before being deformed by Acadian tectonic activity. The Munster Basin developed as a half-graben structure in response to post-Acadian north–south extension in the region. Thus, the Irish ORS provides insights into the region's tectonic history owing to its temporal and spatial proximity to the Caledonian ( c . 475–425 Ma), Acadian ( c . 400–390 Ma) and Variscan orogenic events ( c . 390–290 Ma). This study presents the first detrital zircon and apatite U–Pb geochronological data for the Upper ORS (UORS) in southern Ireland in addition to detrital white mica 40 Ar/ 39 Ar geochronological data to help unravel the depositional history of the Irish UORS and to assess the possible role of sedimentary recycling in Late Devonian basin development. Most UORS samples contain few late Neoproterozoic detrital zircon grains and are instead dominated by early Paleozoic and c. 1.1 Ga zircons. These populations represent recycling of northerly-derived Ordovician to Silurian strata of the Southern Uplands–Longford–Down terrane, which are of Laurentian affinity, and not recycling of Lower ORS (which contains a significant number of late Neoproterozoic detrital zircons) as previously thought. Similar detrital zircon dates have been observed in Givetian–Frasnian quartzites of the Pulo do Lobo Zone on the Iberian Peninsula, providing a possible Rheic Ocean link with the UORS.

First multi-proxy chronostratigraphy of the lower Cambrian Byrd Group, Transantarctic Mountains and correlation within East Gondwana

Antarctica and Australia were sutured together at the equator during the major pulse of animal biodiversification associated with the Cambrian radiation. However, the lack of detailed systematic chemostratigraphic and biostratigraphic sampling of lower Cambrian sedimentary successions from Antarctica has significantly impeded precise age determination and correlation with Cambrian strata on other palaeocontinents. This study is the first to present integrated, simultaneously sampled biostratigraphic and chemostratigraphic (δ13C isotopes) data from the same measured stratigraphic sections through the lower Cambrian Byrd Group in the Transantarctic Mountains. Shelly fossil assemblages (brachiopods, tommotiids, molluscs, bradoriids, trilobites) from the Holyoake Range and Churchill Mountains facilitate direct correlation with the Dailyatia odyssei Zone of South Australia (Cambrian Stages 3–4), and trilobites provide strong correlation between the Starshot Formation and the Cymbric Vale Formation in western New South Wales. A new ID-TIMS radiometric date of 514.96 ± 0.16 Ma from a tuff in the lower Cymbric Vale Formation is similar to dates from tuff beds in the Third Plain Creek Member of the Mernmerna Formation in the Flinders Ranges, providing an important absolute-age tie point between these lower Cambrian successions. Chemostratigraphic data from the upper Shackleton Limestone in the Holyoake Range capture a negative δ13C excursion that can be correlated to negative values within the multi-peaked MICE (cycles V–VIII in Siberia). Integrated faunal and chemostratigraphic data indicate a Cambrian Stages 3–4 age, giving robust chronostratigraphic context for the upper Shackleton Limestone–Holyoake Formation–Starshot Formation succession for the first time, permitting reconstruction of the depositional history of the lower Cambrian of Antarctica and global correlation of Byrd Group strata.

Decoding regressive depositional history from the Neoproterozoic Panium Sandstone Formation, Kurnool Group, India using ‘sequence stratigraphy’ analysis and detrital zircon geochronology

The Neoproterozoic Panium Sandstone Formation of the Kurnool Group (India) offers a unique scope for understanding regressive depositional history in a Neoproterozoic clastic shoreline. It is divided into two ‘Systems Tracts’ namely forced regression and lowstand. Process-based facies and paleo-environmental analysis identified twelve different facies types; grouped under four facies associations (FA I–IV) belonging to both continental and shallow-marine domains viz. distal braided fluvial, swash bar-foreshore runnel, upper shoreface bar-trough, and lower shoreface bar-interbar. Whereas the fluvial deposit (FA I), sharply and erosionally overlying the argillaceous shelf succession of the Owk shelf shale, represents the product of forced regression, the wave-dominated shallow marine deposits (FA II, III and IV) record the depositional history of lowstand in the coastline. A basin ward transition from unconformity (base of FA I) to correlative conformity (base of shallow marine deposits FA II, III, and IV) is documented. The shoreline had a north-northwest to south-southeast alignment and the north-eastward flowing fluvial system met the shoreline at a high angle. Detrital zircon geochronology from the Panium fluvial sandstone allowed documentation of Paleoproterozoic (~2050 Ma–1800 Ma) and Mesoproterozoic (~1500 Ma to ~1200 Ma) age clusters, in addition to earlier documented age clusters from the Banganapalle alluvial sandstone present at the basal part of Kurnool succession. The new age data suggest an addition of new provenances and in turn, tectonic intervention behind the regression in the Kurnool coastline that triggered Panium deposition. Further, the Paleoproterozoic age cluster, obtained from the Panium fluvial deposit, helped in the justification of solitary zircon grain occurrences within the Owk Shale, as described in earlier studies.

BIOSTRATIGRAPHY, PALEOENVIRONMENT AND HYDROCARBON POTENTIAL OF FIKA MEMBER OF PINDIGA FORMATION, GONGOLA SUB-BASIN, NORTHERN BENUE TROUGH, NE NIGERIA

The Fika Member, a crucial stratigraphic unit within the Pindiga Formation, represents a significant geological entity with substantial implications for understanding the regional paleoenvironmental evolution and hydrocarbon prospectivity. This study integrates biostratigraphic analyses, sedimentological investigations, and hydrocarbon potential assessments to elucidate the depositional history, paleoenvironmental conditions, and source rock prospect of the Fika Member. Facies and their stratigraphical distribution analyses were conducted on the Fika Shale exposed mainly at Gabukka Stream 1 and 2. Twenty (20) samples collected were subjected for standard palynological and foraminifera analyses. A standard method of palynomorphs extraction that involves the use of Hydrofluoric and Hydrochloric acid was employed. For foraminifera analysis, washing and sieving method was used. It was discovered that agglutinated foraminifera are the dominance taxa in ten (10) out the twenty (20) samples studied. Based on the colours of the agglutinated foraminiferal and Foraminiferal Color Index (FCI) values suggest low thermal maturity for both oil and gas generation. The foraminiferal assemblages indicate marginal marine (fluvio marine) to shallow inner neritic environments. This is supported by the sedimentological data which indicates a shallow marine depositional environment. The biostratigraphic data suggest Santonian age for the Fika Member.

Quartz luminescence sensitivity enhanced by residence time in the critical zone

The emerging use of quartz luminescence properties to characterize Earth-surface processes shows promise, with optically stimulated luminescence (OSL) sensitivity proposed as a valuable tool for provenance or sediment history tracing. However, the geologic processes that lead to quartz sensitization remain unclear. Here we study the impact of source rock and surface processes on the luminescence properties of quartz sand from bedrock and modern and Late Pleistocene alluvium generated from a mountainous catchment in northern Utah, USA. Continuous wave and linear modulated OSL are used to characterize the luminescence sensitivity and intensity of the fast-decay component. We compare the OSL sensitivity with sand-grain provenance and with proxies for surface processes such as topographic metrics, cosmogenic 10Be-derived erosion rates, chemical weathering indices, and magnetic susceptibility. Late Pleistocene sediment has low OSL sensitivity and a weak fast-decay component, similar to bedrock samples from the source area. In contrast, modern alluvium is dominated by the fast-decay component and has higher and more variable OSL sensitivity, with no clear relationship to upstream bedrock source. There is, however, an inverse relationship between OSL sensitivity and catchment-averaged erosion rates and a positive relationship with chemical weathering indices and magnetic susceptibility. These metrics suggest that the modern alluvium has experienced increased residence time in the shallow critical zone compared to the Late Pleistocene sediments. We suggest that changes in hillslope processes between the effectively wetter, cooler Pleistocene and the dryer, warmer conditions of the Holocene enhanced the luminescence properties. The results suggest that climatic controls on rates and processes of chemical and mechanical weathering and sediment transport and residence within the critical zone are encoded in the luminescence properties of quartz sand.

Observations of Igneous Subsurface Stratigraphy during the Jezero Crater Floor Rapid Traverse from the RIMFAX Ground-penetrating Radar

Perseverance traversed the eastern, northern, and western margins of the Séítah formation inlier on the rover’s western fan front approach. Mapping the stratigraphy and extent of the Máaz and Séítah formations is key to understanding the depositional history and timing of crater floor resurfacing events. Perseverance's rapid progress across the Jezero crater floor between the Octavia E. Butler landing site and the western fan front resulted in limited contextual images of the deposits from the Navigation Camera and Mast Camera Zoom. By combining the limited surface images with continuous subsurface sounding by the Radar Imager for Mars’ Subsurface Experiment (RIMFAX) ground-penetrating radar, Jezero crater floor stratigraphy was inferred along this rapid traverse. We produced the first subsurface map of the Máaz formation thickness and elevation of the buried Séítah formation for 2.3 km of the rapid traverse. Three distinct reflector packets were observed in RIMFAX profiles interspersed with regions of low-radar reflectivity. We interpret these reflector packets with increasing depth to be the Roubion member of the Máaz formation (covered in places with regolith), the Rochette member, and the Séítah formation. We found a median permittivity of 9.0 and bulk density of 3.2 g cm−3 from hyperbola fits to RIMFAX profiles, which suggests a mafic composition for Máaz and Séítah. The low-radar reflectivity regions within each reflector packet could indicate potential depositional hiatuses where low-density material like sediment or regolith could have accumulated between successive Máaz formation lava flows and the Séítah formation at depth.

U-Pb dating of Barra Velha carbonates reveals the influence of Santos Basin sedimentary and tectonothermal history on pre-salt carbonate ages

The depositional age and diagenetic history of the Upper Barra Velha carbonates are poorly understood. To clarify the geochronology of these events and the behavior of the U-Pb isotopic system in carbonates, we conducted an integrated petrographic, QEMSCAN imaging, and in situ U-Pb dating study of calcites and dolomites from the Barra Velha Formation, in the central Santos Basin (SE Brazil). Our results span three geochronological intervals, which are ∼125 Ma, ∼116-114 Ma, and ∼105-100 Ma. The U-Pb isotopic system of calcite allochems was disturbed, yielding ages of ∼115 Ma and ∼105-100 Ma. These ages coincide with magmatic and hydrothermal events in the pre-salt. Dolomites showed that geochronological disturbance of carbonate components may not be pervasive but rather related to fluid-rock interactions and properties of rocks and their constituents such as mineralogy, porosity and permeability. This is evidenced by the U-Pb system of non-porous, non-permeable, and less reactive dolomitic aggregates remaining undisturbed. Eodiagenetic microcrystalline and fine dolomite rhombs provided evidence of Barremian ages, challenging the belief that the Upper Barra Velha deposits are Aptian. Other eodiagenetic dolomites occur as ∼117 Ma eodiagenetic lamellar dolomites, as pseudomorphic dolomites that underwent U-Pb alteration at ∼100 Ma, and as ∼112 Ma pervasive rhombohedral dolomites associated with Mg-rich fluids percolation in the Upper Barra Velha carbonates. Blocky dolomite and saddle dolomite cements have ages of ∼100 Ma, with saddle dolomite constraining the latest silicification event as > 100 Ma. This research elucidates significant geological events, processes, and factors (including magmatic activity, hydrothermal alteration, fluid-rock interactions, and petrographic and mineralogical controls) that influenced the ages of the Upper Barra Velha carbonates. Moreover, it aids in reconstructing the depositional and diagenetic history of the Barra Velha Formation and enhances the understanding of the Santos Basin tectonothermal evolution.

Enhanced classification of pyrite generations based on mineral chemistry using uniform manifold approximation and projection (UMAP)

Trace element signatures are tracked to unravel the genetic history of ore deposits in several mineral systems. This is particularly true for pyrite, a ubiquitous component of many ore-forming systems, including orogenic gold deposits. Here, we critically compare the efficacy of utilizing Uniform Manifold Approximation and Projection (UMAP) versus Principal Component Analysis (PCA) as dimensionality reduction tools applied to a 31 element dataset collected using Laser Ablation Inductively Coupled Mass Spectrometry of pyrite grains from the Kibali gold district (Democratic Republic of Congo). Because of the non-linearity inherent to mineral chemistry and because of its superior preservation of local (distances within clusters) and global (separation between clusters) data relationships, the UMAP approach outperforms dimensionality reduction by PCA. We further present a workflow in which UMAP dimensionality reduction is followed by k-means clustering to guide the classification of pyrite generations in the Kibali case study. Validating this approach with trace elements and UMAP + k-means on a seed-by-seed petrography basis shows that the workflow significantly enhances the original pyrite classification, previously based on texture. This study thus emphasizes the utility of employing advanced statistical analysis methods to capture the intricate nature of pyrite formation. These findings will shape best practices for handling large multi-element datasets in pyrite mineral chemistry studies and are extrapolatable to other mineral systems in which trace element signatures are used to infer the conditions of ore deposit genesis.

Sedimentation record of a complete glacial-interglacial cycle: Down-slope deposits, contourites and plumites of the North Sea trough mouth fan

Trough mouth fans (TMFs) are major submarine depocentres that form in front of ice streams advancing onto the continental shelf, and they provide extensive records of past glaciations and ice-sheet dynamics. However, early research about TMFs was conducted using primarily 2D seismic data, which limits the insights on the deposit's geometries and internal structures and more recent studies using 3D data have focused on the general depositional history of TMFs. Here, we assess the spatial and temporal changes of the glacio-marine landforms and deposits throughout the last glacial-interglacial cycle (Marine Isotope Stage (MIS) 6 to 1, ∼130 ka to present) recorded in a >550 m thick progradational sequence. We use 3D reflection seismic data with significant vertical resolution (up to 2 m) imaging over 14000 km2 from the uppermost North Sea Fan (NSF) to document the seismic stratigraphy and sedimentary processes, by combining horizon picking and geomorphological analyses. The studied interval comprises five mappable units, four on the slope and one on the shelf, spanning from the modern seabed down to the top of the Tampen Slide (∼130 ka). Five different channel types (here included slide scars), as well as contourite and plumite packages are described based on their seismic facies, morphology, geometry, and stratigraphical position. We propose that contour currents are responsible for sediment delivery after the Tampen Slide deposition during the interglacial period before the onset of the Last Glacial Maximum, when high meltwater influx from the shelf produced turbidites. Sedimentation became debris-flow-dominated towards the end of the period of shelf-edge glaciation. The deglacial interval is characterized by the deposition of plumites on the slope. On the shelf, subglacial tills are deposited during both glacial and deglacial periods. We calculate an average sedimentation rate of <1 m/kyr during the interglacial (MIS 5-3), and around 50–65 m/kyr during the glacial and deglacial periods (MIS2-early MIS1). Thus, we document a change of two orders of magnitude in sedimentation rate during a glacial cycle on the slope of a glaciated margin.

Sedimentary organic matter applied to paleoenvironmental reconstruction of the Devonian of the Paraná Basin, SW Gondwana

The study of sedimentary organic matter (SOM) is essential for understanding paleoenvironmental conditions and depositional settings of geological formations. This paper explores the Devonian strata of the Paraná Basin, utilizing SOM analysis to reconstruct paleoenvironments and identify global events. The Devonian period is notable for significant geological and biological changes, including mass extinctions and extensive organic-rich sediment deposition. By examining the composition, distribution, and diagenesis of SOM in this region, we aim to elucidate the paleoenvironmental dynamics and depositional history. The Devonian outcrops in the state of Mato Grosso do Sul, Brazil rocks reveal distinct depositional characteristics, when compared to those found on the eastern border of the basin. The palynofacies analysis was conducted on 59 samples from four outcrops (MS-26, MS-29, MS-30 and MS-70), which age spans from Pragian to Givetian. The main groups and subgroups of the SOM were identified: amorphous organic matter (AOM) (“amorphous organic matter” and pseudoamorphous), phytoclasts (opaques, non-opaque-non biostructured, cuticles, membranes and Spongiophyton) and palynomorphs (spores, freshwater algae, scolecodonts, chitinozoan and acritarchs). The SOM was grouped into three palynofacies associations: opaques, land-derived and marine+AOM. In the Pragian—Emsian interval (MS-26, MS-29 and MS-30), a prevalent occurrence of phytoclasts and marine microphytoplankton is noted, with their distribution exhibiting distinct alternations in each section suggesting a deposition in the marine environment ranging from onshore to offshore. In the Givetian (MS-70 outcrop), we detected a progressive increase and diversification of marine elements (e.g., acritarchs), indicating a transgressive phase probably related with the Kačák event.

Sedimentation history linked to global change in the alpine Damqu Wetland of the Yangtze River headwater in interior Tibetan Plateau

Located in the interior of the Tibetan Plateau (TP) and at the headwaters of the Yangtze River, the Damqu Wetland ranks among the world's highest and is highly sensitive to global climate change. Due to its remoteness and harsh, uninhabitable conditions, the sedimentological and geomorphological studies are still absent by far. Establishing a reliable chronology for sediments is crucial for this unique geographic region. Here we initiated this effort and focused on two riverbank profiles, located in the southeastern of the alpine Damqu Wetland, DQ1 (4.8 m in depth) and DQ2 (3.3 m in depth). A combination of chronological methods, including quartz Optically Stimulated Luminescence (OSL), K-feldspar post-IR InfraRed Stimulated Luminescence (pIRIR), and radiocarbon dating methods, as well as magnetic susceptibility and particle size analysis, were conducted on these profiles to establish the depositional history and reveal the palaeoenvironmental conditions of the Damqu Wetland. The dating results indicate that profiles DQ1 and DQ2 were deposited during ∼59–0.20 ka and ∼265–1.12 ka, respectively. It is interesting to note that the D0 of quartz OSL growth curve has a value as high as 129 Gy. Both profiles exhibit depositional hiatuses, with time gaps between 37 ± 2 and 2.9 ± 0.2 ka for DQ1 and between 265 ± 16 and 4.8 ± 0.4 ka for DQ2, likely due to fluvial erosion during the period of from deglaciation to middle Holocene. The resumed sediment accumulation since the mid-late Holocene is probably mainly attributed to declined fluvial erosion in response to reduced rainfall. The darker sediment layers at depths of 0.9 m–0.7 m and 0.3 m–0.1 m in DQ2, combined with magnetic susceptibility and particle size analyses results, suggest two regional climatic optimum periods at around 4.5 ka and 1 ka. Overall, our research establishes the chronological framework of the Damqu wetland since the Late Quaternary and highlights the significant impact of climate changes on fluvial processes and wetland evolution in the remote interior TP.

Dating the middle and late Quaternary Caspian Sea-level fluctuations: First luminescence data from the coast of Turkmenistan

The Caspian region provides the basis of the stratigraphy and palaeogeography of the Pleistocene of Central Eurasia, and has been actively studied for more than 200 years. Many issues concerning the palaeogeographic history of the various basins of Caspian Quaternary remain unsolved, but the main problem centres on uncertainties in the chronology. Previous chronological studies have focused on a detailed description of the sedimentation history in the Lower Volga and Eastern Caucasus, ignoring a number of unique sites on the eastern Caspian coast, mainly due to inaccessibility. We obtained access to one of the most complete sections, western Cheleken, located on the Caspian coast of Turkmenistan. Within this sandy and generally lowland coast, the western part of the Cheleken peninsula forms a 10 km wide cliff opening a unique series of Middle Pleistocene - Holocene sediments which record in detail the history of Caspian transgressions and regressions. Stratigraphical, geomorphological and palaeontological studies of the section were supplemented with luminescence and radiocarbon dating. Analysis of Caspian molluscs and luminescence ages allowed the reconstruction of the sedimentary history of this region during one of the most important events of the Caspian Basin: the Early and Late Khazarian, Khvalynian and Novocaspian transgression/regression series. Luminescence dating of quartz and feldspar provided 12 OSL, IR50 and pIRIR290 ages, comparison of which showed that quartz grains were sufficiently bleached before deposition. Our chronology provides, for the first time, a deeper understanding of the sedimentation and environmental history in this region and the entire Caspian Sea. The Early Khazarian transgression occurred here at ∼220–200 ka (MIS 7). The Late Khazarian stage recorded in shallow-marine clays had relatively stable level ∼150–130 ka ago. In the second half of MIS 5 sea-level decreased and sedimentation was controlled by a large river, most probably the palaeo-Amu-Daria. The Early Khvalynian stage started at ∼27 ka and continued presumably until ∼14 ka.

Forest floor environment overrules global change treatment effects on understorey communities in a mesocosm experiment.

Light availability profoundly influences plant communities, especially below dense tree canopies in forests. Canopy disturbances, altering forest floor light conditions, together with other environmental changes such as climate change, nitrogen deposition and legacy effects from previous land-use will simultaneously impact forest understorey communities. Yet, knowledge on the individual effects of these drivers and their potential interactions remains scarce. Here we performed a forest mesocosm experiment to assess the influence of warming, illumination (simulating canopy opening), nitrogen deposition and soil land-use history (comparing ancient and post-agricultural forest soil) on understorey community composition trajectories over a 7-year period. Strikingly, understorey communities primarily evolved in response to the deeply shaded ambient forest conditions, with experimental treatments exerting only secondary influences. The overruling trajectory steered all mesocosms towards slow-colonizing forest specialist communities dominated by spring geophytes with lower nutrient-demand. The illumination treatment and, to a lesser extent, warming and agricultural land-use legacy slowed down this trend by advancing fast-growing resource-acquisitive generalist species. Warm ambient temperatures induced thermophilization of plant communities in all treatments, including control plots, towards higher dominance of warm-adapted species. Nitrogen addition accelerated this thermophilization process and increased the community light-demand signature. Land-use legacy effects were limited in our study. Our findings underscore the essential role of limited light availability in preserving forest specialists in understorey communities and highlight the importance of maintaining a dense canopy cover to attenuate global change impacts. It is crucial to integrate this knowledge in forest management adaptation to global change, particularly in the face of increasing demands for wood and wood products and intensified natural canopy disturbances.