Depositional History Research Articles

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.

Application of palynomorphs and palynofacies in Early Cretaceous paleoenvironmental reconstruction; Shushan Basin, Egypt

An integration of palynomorph and palynofacies data from the Shushan-1X well is used to infer the paleoenvironmental conditions of the Valanginian to Middle Cenomanian (Cretaceous) section of the western Shushan Basin, northern Egypt. The data obtained contribute significantly to the depositional history of the basin. The low diversity of dinoflagellate cyst assemblages, along with the dominance of land-derived spores and pollen, suggest restricted (marginal) marine environments, in contrast to their coeval representatives from the Tethyan Realm. Open marine (inner shelf) environments developed at a few horizons in the Dahab and Bahariya formations, partly contemporary with the global Aptian and Cenomanian eustatic cycles. These environments were relatively more offshore than those described in the eastern and southeastern parts of the basin. The study of total palynological organic matter (TPOM) has contributed largely to these established environmental settings. It has also allowed the recognition of redox (suboxic to anoxic) conditions and the impact of a large magnitude of terrigenous influence.

What has Changed in 20 Years? Structure and Function of Soft-sediment Macrofauna in a Subarctic Embayment, Newfoundland (Canada)

Understanding how natural and anthropogenic disturbances affect the structure and functioning of marine ecosystems is central to predicting future dynamics. Placentia Bay is an Ecologically and Biologically Significant Area (EBSA) in the North Atlantic exposed to multiple stressors (e.g., rising sea surface temperatures, tanker traffic, and aquaculture). To investigate changes in the community and functional structure of soft-sediment macrofauna as well as environmental drivers of observed variation, we compared contemporary (2019–2020) and historical (1998) samples at eight stations (n = 77) collected 21 years apart. Although community and functional structure differed between these time points, functional traits were maintained (i.e., no loss of 36 trait modalities). Overall, 37% of species/taxa were only observed in either the historical or contemporary community, and the contemporary community exhibited lower macrofaunal density but had similar richness, resulting in higher evenness and diversity. Highly tolerant subsurface deposit feeders having small body sizes (< 10 mm) and direct development dominated the historical community. The contemporary community had nearly equal proportions of surface and subsurface deposit feeders with small to medium body sizes (< 10–50 mm) with pelagic larvae, and the proportion of highly tolerant species/taxa was reduced. These changes likely reflect the reduction in polychaetes (91 vs. 58%) and increased bivalves (4 vs. 25%) relative to the historical time point. Community variation was driven by changes in the sedimentary habitat. Contemporary versus historical sediments were ~ 4.5x coarser (possibly due to storms) with higher levels of sedimentary organic matter. This work contributes to advancing the understanding of relationships between benthic macrofauna, functional traits, and the sedimentary habitat in coastal environments.

Revised OSL chronology of the Kisiljevo loess-palaeosol sequence: New insight into the dust flux in the eastern Carpathian Basin during MIS 3 - MIS1

This study presents a detailed investigation of the Kisiljevo loess-palaeosol sequence in north-eastern Serbia, offering a refined understanding of its paleoenvironmental dynamics. Contrasting our updated OSL chronology with a previous study, reveals discrepancies, particularly at 400 cm depth, where a considerable age underestimation is evident. While variations in sampling depth and methodology may contribute to some differences, the substantial deviation raises concern about the reliability of the earlier chronology. Our robust age-depth model constructed using Bayesian modelling, and the consistent increase in ages with depth suggest a potential underestimation in the uppermost layer of the earlier study, possibly due to partial bleaching or post-depositional mixing. The Bayesian age-depth model portrays a continuous sedimentation history from the later stages of Marine Isotope Stage 3 (MIS 3) to the present day. The patterns in the calculated Mass Accumulation Rates reveal distinctive peaks during MIS 3 and the middle of MIS 2, deviating from typical dust deposition models. The MIS 3 peaks in dustiness could be attributed to regional factors such as increased transportation rates, enhanced trapping efficiency, or elevated palaeowind intensity. This research not only enhances our understanding of the Kisiljevo LPS but also provides valuable insights into regional paleoenvironmental dynamics. The study emphasizes the importance of considering local geological variations in reconstructing past climates from sediment archives and sets the stage for further investigations into the factors influencing dust deposition in north-eastern Serbia. The MAR trends established here serve as a crucial reference for broader paleoclimatic interpretations in the Carpathian Basin.

Organic petrology and geochemistry data reveal depositional and thermal history of coal in the Guaduas formation, Colombian Eastern Cordillera

Colombia is a country rich in coal deposits; however, there are few published studies characterizing these coals in detail from a scientific perspective. This study investigates the thermal maturity and depositional environment of a coal seam from the Guaduas formation (Maastrichtian-Paleocene) of the Eastern Colombian Cordillera Basin, providing insight into burial and temperature history and changes in the depositional environment over time. This three-meter-thick hard coal seam reflects about 20 m of former peat deposition, representing a period of roughly 10.000 years.Five large, fresh samples (A to E) were collected from the seam every thirty centimeters and divided into seventeen sub-samples analyzed using organic petrological methods, Rock-Eval pyrolysis and organic geochemistry. Different thermal maturity- and depositional environment-related parameters have been determined. Results reveal a maturity of approximately 0.9% vitrinite reflectance, and relatively high HI values (kerogen type II-III). Correspondingly, high values of νCHx over γCH indicate a high relative abundance of aromatic rings over aliphatic groups. Moreover, high CH2/CH3 ratios suggest long and simple aliphatic chain structures. Molecular data indicate a balanced odd- over even n-alkane distribution and a high amount of long-chain n-alkanes. High Pr/Ph ratios and hopanoid biomarkers reveal an oxidizing depositional environment. The coal seam investigated in this study is characterized by low ash yields and low sulfur contents particularly in the central part of the seam, while percentages of inertinite are high (up to 54 Vol.-%). This data supports a low water table and oligotrophic, raised bog conditions during deposition in a humid, tropical climate which is consistent with the almost equatorial position of the study area during deposition of the Guaduas Formation. Water was mainly supplied via rainfall leading to overall low ash yields. In contrast, the top of the coal seam is strongly enriched in sulfur revealing that rapid marine flooding ultimately ceased peat accumulation leading to authigenic pyrite formation.

Geosites and Climate Change—A Review and Conceptual Framework

Geosites are windows into the geological past, which may be recorded in rocks and their properties, the fossil content, and landform produced by processes no longer operating. Since the histories of sedimentation, life, and landscape evolution are to a certain extent controlled by climatic conditions, some geosites may be used as illustrations of various themes linked to the issue of climate change. In this paper, a coherent systematic framework is proposed for how to look at geosites through the lens of climate change. Four major aspects of relevance are recognized: (i) geosites providing evidence of changing climatic conditions in the past; (ii) geosites providing evidence of an environment different than that of today at the place; (iii) geosites providing evidence of extreme weather events; and (iv) dynamic geosites, subject to change as a response to ongoing climate change. The use of geosites to raise awareness and educate the public about climate change faces various interpretation challenges. In particular, linking with ongoing climate change requires caution and balanced presentation as most geosites record changes which occurred without any anthropogenic component. The preferred focus should be on environmental instability in general rather than on any specific reasons for change.

Historical sedimentary and evolutionary characteristics of POPs and EDCs in typical regions of the three Gorges reservoir, China

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10–93.67 μg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored.

Sedimentation History of the Aldan–Maya Sedimentary Basin (Southeast of the North Asian Craton) Reconstructed from a Seismostratigraphic Section

Sedimentation History of the Aldan–Maya Sedimentary Basin (Southeast of the North Asian Craton) Reconstructed from a Seismostratigraphic Section

Palynological study of some Afowo bituminous sediments in parts of Southwestern Nigeria

The tar sand and shale sequences of the Afowo Formation exposed at Lore, Shagbon, and Gbegude areas in parts of southwestern Nigeria has been palynologically investigated to unravel the depositional history. The lithofacies assemblage of the studied section comprising of shale, siltstone, claystone, lignites and ferruginised facies and their peculiar sedimentological features indicate low energy quiet setting, ranging from fresh water to nearshore marine swamps. Recovered palynomorph assemblage include marine dinoflagellate cyst such as Paleocystodinium golzowenses, Lycopodium spp. of Maastrichtian age. The pollen and spore (Retidiporites magdalenensis, Echimonocolpites, Echitriporites trianguliformis and C-cristatus) indicate terrestrial fresh water environment. The abundance of palmea pollen (Echitriporites and Longapertites) and the pteridophyte suggest that the vegetation developed under a predominant humid climate.

The Yellowknife greenstone belt and underlying Central Slave Cover Group, Slave craton, Canada: constraints and questions arising from a U-Pb dating study

Legacy U-Pb isotopic data are reported for the Mesoarchean Central Slave Cover Group and Neoarchean Yellowknife greenstone belt, Slave craton, Northwest Territories, Canada. In two locations north of the City of Yellowknife, exposures of cover group rocks occur beneath mafic volcanic and subvolcanic units traditionally assigned to the basal Chan Formation of the Kam Group. Both cover group occurrences contain felsic volcanic tuff units that yield eruption ages of 2853 +2/-1.5 Ma and 2826 ± 1.5 Ma. The younger tuff is underlain by felsic volcaniclastic schist with a dominant, basement-aged detrital zircon population that was deposited after 2840 ± 6 Ma. Near the south end of the exposed greenstone belt, a felsic tuff within the Octopus Formation provides an age of 2699 ± 3 Ma, confirming that this formation is not part of the Central Slave Cover Group. A pillowed basalt flow within the Chan Formation is cut by a composite gabbro dyke dated as 2738 +3.5/-3 Ma. However, a more general ca. 2730-2740 Ma age interpretation for this dyke may be appropriate due to the potential for complex lead loss behaviour in the dated baddeleyite fractions. Younger U-Pb zircon and monazite ages reported herein (2710-2706 Ma) contribute to our understanding of felsic magmatic and gold-mineralizing events that influenced later development of the Yellowknife greenstone belt. Although the depositional history of the autochthonous Central Slave Cover Group is becoming better known, questions remain regarding the age and tectonomagmatic affinity of adjacent mafic volcanic rocks traditionally assigned to the Kam Group and correlative assemblages. Are some of these rocks actually part of the Central Slave Cover Group?

Osteopontin stabilization and collagen containment slows amorphous calcium phosphate transformation during human aortic valve leaflet calcification

Calcification of aortic valve leaflets is a growing mortality threat for the 18 million human lives claimed globally each year by heart disease. Extensive research has focused on the cellular and molecular pathophysiology associated with calcification, yet the detailed composition, structure, distribution and etiological history of mineral deposition remains unknown. Here transdisciplinary geology, biology and medicine (GeoBioMed) approaches prove that leaflet calcification is driven by amorphous calcium phosphate (ACP), ACP at the threshold of transformation toward hydroxyapatite (HAP) and cholesterol biomineralization. A paragenetic sequence of events is observed that includes: (1) original formation of unaltered leaflet tissues: (2) individual and coalescing 100’s nm- to 1 μm-scale ACP spherules and cholesterol crystals biomineralizing collagen fibers and smooth muscle cell myofilaments; (3) osteopontin coatings that stabilize ACP and collagen containment of nodules preventing exposure to the solution chemistry and water content of pumping blood, which combine to slow transformation to HAP; (4) mm-scale nodule growth via ACP spherule coalescence, diagenetic incorporation of altered collagen and aggregation with other ACP nodules; and (5) leaflet diastole and systole flexure causing nodules to twist, fold their encasing collagen fibers and increase stiffness. These in vivo mechanisms combine to slow leaflet calcification and establish previously unexplored hypotheses for testing novel drug therapies and clinical interventions as viable alternatives to current reliance on surgical/percutaneous valve implants.

Insights into the Phanerozoic evolution of the São Francisco Craton based on detrital zircon thermochronology and U-Pb-Hf geochronology

Basins within cratonic environments offer valuable insights into the fragmentation, dispersion, and agglutination of the lithosphere within supercontinents. The southern São Francisco Craton is home to sedimentary basins that formed in both intraplate tectonic settings (late Paleoproterozoic to Neoproterozoic and Mesozoic) and convergent tectonic settings (Ediacaran to Cambrian). To elucidate the Phanerozoic thermal history of the craton and the long-term depositional history of the southern São Francisco Craton’s cover, a comprehensive study was conducted utilizing detrital zircons through zircon fission-track (ZFT) thermochronology and U-Pb-Hf geochronology. This study analyzed samples from the following units: (1) the intracratonic basin—Lower and Upper Espinhaço Supergroup, with depositional age intervals ranging 1800−1600 Ma and 1200−920 Ma, respectively; (2) the rift-related passive margin basin—Lower Macaúbas Group (720 Ma and 640 Ma) and Jequitaí Formation, which is likely of Cryogenian age (650−635 Ma); (3) and the foreland basin—Bambui Group and Três Marias Formation, with ages of ca. 600−520 Ma and 520−480 Ma, respectively. U-Pb-Hf detrital zircon geochronology revealed the complex depositional history of the southern São Francisco Craton, and indicated changing source rocks over time. Conversely, the ZFT analysis of Precambrian to Cambrian samples allowed for the identification and characterization of Phanerozoic events in the southern São Francisco Craton. These events include: (1) the exhumation and late orogenic uplift of the foreland at ca. 500−480 Ma (mean age of 499 ± 5.5 Ma) during the late stages of the Brasiliano−Pan-African Cycle, which was associated with the Araçuaí Belt and lithospheric rebound of the peripheral cratonic margin of the southern São Francisco Craton; and (2) an age of 330−280 Ma (mean age of 306.6 ± 4.8 Ma) that possibly resulted from ice retreat and isostatic rebound interior of the Gondwana Paleocontinent. Additionally, analysis of detrital zircons from the Areado Group shows a later tectonic event recorded at 128.1 ± 9.4 Ma, which indicates Mesozoic intracontinental rifting. Based on these results and interpretations, the timing and exhumation of the southern São Francisco Craton during the Phanerozoic can be attributed to the final stages of the continental collision of the southern São Francisco Craton and Congo Craton and large-scale continental uplift during the Permo-Carboniferous late Paleozoic Ice Age of Gondwana. Overall, the findings demonstrate a direct correlation between known tectonic events at the plate margins of Western Gondwana and periods of cratonic basin formation.

Tracking the tempo of a continental margin arc: Insights from a forearc succession in West Antarctica

The Fossil Bluff Group of eastern Alexander Island records the exceptional preservation of more than 8 km of Mesozoic sedimentary rocks deposited into an accretionary forearc basin that developed unconformably above a late Paleozoic accretionary complex, and in proximity to a continental margin arc during a prolonged phase of enhanced magmatism. Through the Mesozoic, the Fossil Bluff Group evolved from a trench-slope environment to a forearc basin sourced from the continental margin arc. During this period, the Antarctic Peninsula’s convergent margin was characterized by episodes of magmatic flare-ups that developed during tectonic compression, crustal thickening, extension, and uplift. U-Pb and Lu-Hf detrital zircon data are used to determine the provenance of the forearc succession and as a monitor of arc magmatic tempos during the late Mesozoic. The magmatic record in the adjacent arc is poorly preserved or partially absent, but the sedimentary record of the forearc basin preserves a largely uninterrupted record of arc magmatism that can be studied with detrital zircon geochronology and geochemistry. The basal succession of the Fossil Bluff Group is sourced from the adjacent accretionary complex, but thereafter it is strongly controlled by the proximal arc in western Palmer Land and is characterized by a mixed arc/recycled signature during episodes of renewed sedimentation. However, the main phases of deposition during the Early Jurassic (ca. 180 Ma), Early Cretaceous (141−131 Ma), and mid-Cretaceous (125−102 Ma) are dominated by arc-only sources. The Lu-Hf isotopic record supports a transition from convergence to extension and a return to convergence during the Mesozoic, which is consistent with accretionary orogens from elsewhere along the West Gondwanan margin. The provenance record during the depositional history of the basin points overwhelmingly to an autochthonous origin; as such, models for parts of the western province of the Antarctic Peninsula being allochthonous are unsupported.

Chronology by luminescence and radiocarbon on core sediments from the northeastern pearl river plain and implications for delta process

Accurate dating is the basis for deciphering eustatic and climatic changes on deltaic sedimentary processes. In the Pearl River Delta (PRD) plain of south China, scarce robust chronology hinders the detailed interpretation of sedimentary history. In this study, quartz optically stimulated luminescence (OSL) (21 samples), feldspar post-IR IRSL (pIRIR) (4 samples) and radiocarbon (14C) (2 samples) dating were applied to obtain detailed chronological framework of core SXG06 (23-m long to bedrock) from the northeastern PRD. SXG06 consists an upper marine unit (M1) and a lower marine unit (M2), separated by a terrestrial unit (mottled clay, T1). For M1, quartz OSL and 14C samples yielded ages from 5.2 ± 0.3 to 0.32 ± 0.02 ka. The sample on top of T1 produced a quartz OSL age of 35 ± 2 ka. For other 12 samples in T1 and M2, quartz OSL signals reached saturation and generated minimum ages (>51 ka). For these the saturated quartz OSL samples, feldspar pIR50IR250 provides an age range of 123 ± 7–105 ± 7 ka. The compilation of all the above ages and previous sedimentology data reveals that: (1) M2 was formed during marine transgression of Marine Isotope Stage (MIS) 5; (2) A hiatus with an age gap of between ∼35 ka and ∼5 ka was observed, which might be due to the low sea level and resultant weathering scouring; (3) Initial M1 deposits from the northeastern PRD postdated the central and southern PRD by ∼3 ka, indicating delayed delta development in the northeastern PRD during the Holocene. (4) SXG06 experienced slow deposition 0.3 m/ka in ∼5–3 ka because of the coevally decreased sediment supply, followed by accelerated deposition rate of 3 m/ka after ∼3 ka associated with strengthen human activity.

A middle Miocene to Quaternary sedimentary and palaeoenvironmental record from the western continental shelf of South Africa

The sedimentary record of the western South African continental shelf is condensed compared to the continental slope and contains erosional unconformities, owing to periods of non-deposition, eustatic sea-level fluctuations, episodic uplift and intensified continental aridity. Despite this, the sedimentary record of the continental shelf provides important information on the depositional history and palaeoenvironmental evolution of the region. A core retrieved from the western shelf of South Africa was analysed for its sedimentary composition, lithological variation, foraminiferal content and its relation to the palaeoenvironment of the region. Four depositional facies were identified along the core, namely quartzitic sand, sandy mud, and glauco-phosphatic sand and a glauco-phosphatic gravel. The basal facies consisting of quartzitic sand is interpreted to have been deposited between 15.90 and 14.60 Ma, corresponding to the timing of the Mid-Miocene Climatic Optimum (MMCO). The highly quartzitic nature of the sediments indicate a high terrestrial influence from fluvial sources. The overlying sandy mud facies was deposited between 14.60 and 13.90 Ma based on planktic foraminiferal biostratigraphy. Foraminiferal analyses of these two facies that were deposited in the Langhian stage of the middle Miocene point to subtropical sea surface conditions and mesotrophic benthic environments. Sea level was noticeably higher during the MMCO and part of the cooling period following the MMCO. An erosional surface that spans 10.77 Myr, equal to the late Miocene (13.90 Ma) to early Pliocene (3.13 Ma), marks the boundary between the two Langhian facies and the overlying two Pleistocene facies, consisting of coarser grained glauco-phosphatic gravelly sand units. The Pleistocene environment on the shelf is interpreted to contrast with the Langhian environment, where cooler, shallower conditions and a more eutrophic benthic environment was prevalent, during a time that Benguela upwelling intensified with higher frequency and higher amplitude sea level fluctuations. Palaeobathymetric interpretations indicate that middle Miocene sea-level in the region were up to 77 m higher than present day and 101 m lower in the Pleistocene, in-line with previous global studies. Glauco-phosphatic content that increase up-core also marks the shallowing of the environment under high productivity conditions.

Chronology of core sediments from the south coastal Bohai Sea of eastern Asia and its implications for sedimentary history

The Shandong Peninsula along the coastal Bohai Sea in China is a vast alluvial plain formed by the Yellow River. It is an ideal place for investigating the evolution of landform in a river–sea interaction area where chronology is key. However, detailed optically stimulated luminescence (OSL) chronology studies of cores are still limited and have mainly concentrated on the Yellow River Delta, while they are scarce on the south coast of the Bohai Sea. In this study 16 OSL samples were collected from the upper 32 m of core DZK01 (192 m in depth) to establish a chronological framework using quartz OSL. Results indicated that the quartz OSL ages ranged from 217 ± 19 ka to 1.63 ± 0.14 ka, and we believe they were the minimum ages when De > ca. 200 Gy owing to OSL signal saturation. Our dating results reveal two sedimentary hiatuses with age gaps of 71–37 ka and 37–9.5 ka. Holocene sediments are located above a depth of 11.8 m with an onset age of approximately 9.5 ± 0.6 ka. Based on the sedimentary facies and dating results, no transgression sediment has been observed during marine isotopic stage (MIS) 3. This sedimentary sequence pattern is consistent with global sea-level change. We also summarized the extents of three transgressions around the Bohai Sea, and found very different patterns for different part of the coasts, e.g., in the north, the west, and the south. This requires further investigation.