Sedimentary Archives Research Articles

Magnetostratigraphy of the Niubao Formation in the Bangong‐Nujiang Suture Zone: Constraints on the Amount of Crustal Shortening of the Tibetan Plateau Since 60 Ma

AbstractThe Early Cenozoic sedimentary archives of Tibet are crucial for elucidating the geodynamic processes related to continental collision, particularly crustal deformation and shortening. However, the lack of a reliable chronostratigraphic framework for the Cenozoic sedimentary basins in central Tibet has hindered a comprehensive understanding of the influence of the continuous India‐Asia convergence process on the tectonic evolution of the Tibetan hinterland. Here, we report new magnetostratigraphic ages and paleomagnetic results for the Niubao Formation exposed in the northern bank of the Siling Co. Positive field tests and microscopic observations suggest that the remanence is primary. We determine that the depositional age of the measured section was between 59.2 and 48.6 Ma. Our results reveal that the paleogeographic location of the Bangong‐Nujiang Suture Zone during the Late Paleocene–Early Eocene was 25.4 ± 2.1°N, thus supporting the model of two‐stage collision between India and Asia.

Metagenomic analysis of sedimentary archives reveals ‘historical’ antibiotic resistance genes diversity increased over recent decades in the environment

Abstract Antibiotic Resistance Genes (ARGs) are widespread in freshwater environments and represent a concealed threat to public health and aquatic eco-system safety. To date, only a limited number of studies have investigated the historical distribution of ARGs and their hosts through the analysis of freshwater sedimentary archives. This research gap constrains our comprehensive of the mechanisms underlying natural bacterial resistance formation during pre-antibiotic era (prior to the 1940s) and the development of human-induced bacterial resistance in post-antibiotic era (since the 1940s). In this study, we examined the vertical distribution patterns of ARGs and their associated hosts within a sedimentary core from a eutrophic lake, employing shotgun sequencing methodology. The findings revealed a marked increase in ARG diversity during post-antibiotic era, and the predominant ARG types identified included those conferring resistance to multidrug, bacitracin, macrolide–lincosamide–streptogramin, beta-lactam, tetracycline, fluoroquinolone, glycopeptide and aminoglycoside, collectively accounting for 78.3%–85.6% of total ARG abundance. A total of 127 ARG subtypes were identified in samples, and 48 ARG subtypes shared across vertical sediment resistome profile with two of them, bacA and bcrA, occurring only in post-antibiotic era. Further, 137 metagenome-assembled genomes (83 species belonging to 12 phyla) were identified as ARG hosts, mainly belonging to the phyla Proteobacteria, Nitrospirota, Chloroflexota, Bacteroidota, Actinobacteriota, Cyanobacteria, and Firmicutes. Significant correlation was found between the diversity of ARG and the concentrations of organic matter and heavy metals, suggesting a common source of contamination. Aside the fact that human-induced eutrophication is a forcing factor acting in parallel to increase ARGs releases in water systems, both being indicators of increased urbanization in the catchment, eutrophication may significantly increase bacterial activity, thereby facilitating the spread of antibiotic-resistant bacteria in environment. This study reveals the marked increased in ARG diversity with the onset of antibiotic use by human societies with potential impact of aquatic ecosystem.

A framework for reconstructing marine heatwaves from individual foraminifera in sedimentary archives

Marine heatwaves (MHWs) are warm sea surface temperature (SST) anomalies with substantial ecological and economic consequences. Observations of MHWs are based on relatively short instrumental records, which limit the ability to forecast these events on decadal and longer timescales. Paleoclimate reconstructions can extend the observational record and help to evaluate model performance under near future conditions, but paleo-MHW reconstructions have received little attention, primarily because marine sediments lack the temporal resolution to record short-lived events. Individual foraminifera analysis (IFA) of paleotemperature proxies presents an intriguing opportunity to reconstruct past MHW variability if strong relationships exist between SST distributions and MHW metrics. Here, we describe a method to test this idea by systematically evaluating relationships between MHW metrics and SST distributions that mimic IFA data using a 2000-member linear inverse model (LIM) ensemble. Our approach is adaptable and allows users to define MHWs based on multiple duration and intensity thresholds and to model seasonal biases in five different foraminifera species. It also allows uncertainty in MHW reconstructions to be calculated for a given number of IFA measurements. An example application of our method at 12 north Pacific locations suggests that the cumulative intensity of short-duration, low-intensity MHWs is the strongest target for reconstruction, but that the error on reconstructions will rely heavily on sedimentation rate and the number of foraminifera analyzed. This is evident when a robust transfer function is applied to new core-top oxygen isotope data from 37 individual Globigerina bulloides at a site with typical marine sedimentation rates. In this example application, paleo-MHW reconstructions have large uncertainties that hamper comparisons to observational data. However, additional tests demonstrate that our approach has considerable potential to reconstruct past MHW variability at high sedimentation rate sites where hundreds of foraminifera can be analyzed.

From Arctic ponds to the "Northern Great Lakes": Algae as first responders of climate-driven regime shifts.

Arctic freshwater ecosystems are on the "frontline" of climate change, but due to a lack of direct long-term monitoring data, indirect approaches, such as algal-based paleolimnology, must be used to reconstruct past limnological conditions. Our understanding of the responses of small- to mid-sized Arctic lakes to climate warming has increased over the last ~30 years. However, until recently, little was known about even the basic limnological conditions of Canada's "Northern Great Lakes," such as Lake Hazen, Great Bear Lake, and Great Slave Lake. In this summary, we show that a continuum of algal changes, observable in the sedimentary archives of shallow ponds to very large Arctic lakes, signals the crossing of key aquatic thresholds linked to changing ice covers and thermal regimes, declining wind speeds, and other climate-related variables. With recent accelerated warming, even the largest and most resilient Arctic waterbodies are now fundamentally different than they were just a few decades ago. These changes will undoubtedly cascade throughout the food web leading to important changes for local Indigenous populations as well as the global community.

A 14,000‐Year Sediment Record of Mercury Accumulation and Isotopic Signatures From Lake Malaya Chabyda (Siberia)

AbstractEurasian permafrost soils contain large amounts of organic carbon (OC) and mercury (Hg), sequestered by vegetation during past and present interglacial periods. Lake sediment archives may help understand past OC and Hg dynamics and how they interact with climate‐related variables. We investigated Hg accumulation, OC dynamics, and Hg and OC stable isotopes in a 14,000‐year sediment record from Lake Malaya Chabyda (Central Yakutia, Russia). Sediment Hg was correlated to OC (p value < 0.01), with lower OC and Hg accumulation rates (OCAR, HgAR) during the cold Younger Dryas (YD, 12,900–11,700 cal BP), when the lake level was low. Elevated sediment Δ200Hg (0.05‰ ± 0.11‰), representing dominant HgII deposition, and low δ13C, indicates low lake primary productivity during the YD. During the early Holocene, Δ200Hg and Δ199Hg decreased, while δ13C, δ202Hg, OCAR, and HgAR increased, suggesting enhanced algal primary productivity in deeper, more turbid waters. From 4,100 cal BP to present, Hg/OC ratios and HgAR increased at constant OCAR, indicating an additional Hg source to the lake. Analysis of Hg isotopes suggests direct Hg0 uptake into lake waters, potentially driven by primary production and efficient Hg burial. Our observations suggest that the gradual climate warming since the Last Glacial Termination and into the early Holocene led to enhanced OC and Hg burial in northern lakes and watersheds. Late Holocene enhanced Hg burial, but not OC, is possibly related to a renewed increase in lake primary productivity. Continued global warming may lead to further Hg sequestration in northern aquatic ecosystems.

Applying geotechnical borehole databases in the search for interglacial deposits in Denmark

Geotechnical investigations conducted in preparation for infrastructure development provide high-quality borehole data in standardised digital formats. In Denmark, such geotechnical borehole data are not required to be reported to the national well database (Jupiter) and are mainly archived in privately owned databases. Accessible interglacial and interstadial terrestrial deposits are rare in Denmark, and these borehole data have the potential to identify interglacial and interstadial deposits, with significant implications for ongoing palaeoclimate, palaeoenvironmental and archaeological research. In this study, we compiled data from six major geotechnical companies, resulting in a database with over 550 000 boreholes. From this database, we identified 1850 boreholes containing samples associated with interglacial and interstadial ages. Through extensive filtering for well-documented lacustrine or palustrine deposits, we selected 161 boreholes and referenced them to 39 different geographical occurrences. Of these 39 occurrences, 36 were either new terrestrial deposits or provided substantial new records to known interglacial and interstadial sites. Our findings demonstrate that access to these privately owned geotechnical borehole data can be a valuable resource for identifying rare near-surface geological deposits, allowing the discovery of several new Pleistocene sedimentary archives that warrant further investigation.

Carbonate mud production in lakes is driven by degradation of microbial substances

Carbonate mud is crucial in the global carbon cycle and serves as a key sedimentary archive for paleoclimate reconstruction. Understanding the mechanisms behind its formation is crucial for explaining long-term carbon storage, including atmospheric carbon dioxide transfer to the hydrosphere and variations in mud production over geological timescales. Various mechanisms explain carbonate mud formation in both lake and marine sediments. Using bio-physicochemical methods on deep sediments of Lake Ilay, Jura, France, we propose a model of micrite formation. Our study shows that micrite mineralization occurs in sediments due to the degradation of ooze rich in exopolymeric substances throughout the sediment core’s depth. This mineralization continues as long as exopolymeric substances are present, persisting for at least 2000 years. Cryo-Scanning electron microscope imaging reveals calcite nucleation at degraded exopolymeric substance nodes, advancing with substance degradation and calcium release. These findings provide insights into fossil carbonate mud origins and formation processes.

Fossil spring records from central Sudan reveal paleoenvironmental and settlement dynamics in the Eastern Sahel during the last 30 ka

Knowledge of past environmental change and prehistoric settlement dynamics in the Sahel east of the Nile is limited due to the scarcity of suitable sedimentary archives and archaeological sites. Here we present tufa-based paleoenvironmental records from the area of NW Butana (central Sudan, ∼55 km southeast of the Nile River) which show that increased rainfall and spring activity occurred in several discrete intervals during the last ∼30,000 years. Lithostratigraphic data combined with phytolith, malacological, paleopedological, and stable carbon isotope records revealed humidity peaks during late MIS3 and the early and middle Holocene. Gaps in lithological records correlated with dry periods of the Last Glacial Maximum and Younger Dryas. Minor wet pulses coinciding with Late Glacial interstadials indicate an early intensification of the African monsoon, which implies that a sharp climatic boundary existed between the Sahel and the Sahara during this period.These new paleoenvironmental records, together with archaeological evidence from Butana, provide a unique opportunity for understanding human ecology in the eastern Sahel. The peoples who inhabited this dryland area 30+ km from the Nile Valley could not rely on its relatively predictable resources of riverine, floodplain and lake habitats. New models of subsistence and settlement, and strategies of adaptations to seasonal and interannual environmental variability are needed.

Pollution trends in a protected fluvial landscape located in a highly industrialized Ostrava urban agglomeration; Rezavka Nature Reserve, Czech Republic

Abandoned meanders and former river channels represent important depositional units of fluvial river systems, making them suitable sedimentary archives for assessing pollution trends. The objective of this study is to provide insight into temporal trends and spatial variability in pollution levels in the selected fluvial elements (an abandoned meander, a former river channel, and a semi-open meander) within the Rezavka Nature Reserve (part of the Poodří protected landscape area) along the Odra River and Mlýnka stream, located in the heavily polluted Ostrava urban agglomeration (Czech Republic). Initial stages of the abandoned meander evolution were characterised by high sediment accumulation rates and decelerated over time, while more regular sediment supply continued in sites close to the semi-open meander of the Mlýnka stream. Pollutants were effectively captured by abandoned meanders with fine-grained infill, while the coarser-grained infill of the former channel was less effective pollutant scavenger. A time frame for deposition was assigned using vertical trends in 137Cs mass activity and selected organic pollutants. The sedimentary record, covering the last ~ 70 years, reveals a distinct vertical pollution trend that reflects industrial development. Pollution levels have increased since the 1950s and will remain high at the end of the 20th century. The depth pattern of heavy metals, as well as their enrichment factors, shows an upward increase. Levels of persistent organic pollutants are typically low or under the limit of detection in the deepest strata, gradually or sharply rising upward.

Using pollen in turbidites for vegetation reconstructions

ABSTRACTTurbidites, deposited by sub‐aqueous gravity flows, are common in sedimentary archives worldwide and present a unique challenge and opportunity when reconstructing past vegetation through pollen analysis. When sampling pollen from a sediment core for palaeovegetation records, it is common practice to target background sediments (i.e. pelagic sediment) and avoid sampling turbidites, as they are presumed to portray a misleading picture of past vegetation. This assumption stems from our limited understanding of pollen abundance and distribution through turbidites, meaning that palynologists overlook deposits that could potentially be used to reconstruct past vegetation and climate. We present pollen assemblage and sedimentological data from four recent (<150 years) deep marine turbidite deposits from the Hikurangi Subduction Margin, Aotearoa‐New Zealand, with the aim of understanding the abundance and distribution of pollen in fine‐grained turbidites. We find that pollen is diluted in the bases of turbidites, but despite this dilution, the proportions of different pollen taxa remain consistent through each turbidite. These results confirm that pollen can be sampled from turbidites for palaeovegetation reconstructions and that sampling the fine‐grained upper parts of turbidites will provide the best pollen recovery.

North Atlantic temperature control on deoxygenation in the northern tropical Pacific

Ocean oxygen content is decreasing with global change. A major challenge for modelling future declines in oxygen concentration is our lack of knowledge of the natural variability associated with marine oxygen inventory on interannual and multidecadal timescales. Here, we present 10 annually resolved 200 year-long records of denitrification, a marker of deoxygenation, from a varved sedimentary archive in the North Pacific oxygen minimum zone covering key periods over the last glacial–interglacial cycle. Spectral analyses on these records reveal strong signals at periodicities typical of today’s Atlantic multidecadal oscillation. Modern subsurface circulation reanalyses regressed on the positive Atlantic and Pacific Climatic Oscillation indices further confirm that North Atlantic temperature patterns are the main control on the subsurface zonal circulation and therefore the most likely dominant driver of oxygen variability in the tropical Pacific. With currently increasing temperatures in the Northern Hemisphere high latitudes and North Atlantic, we suggest deoxygenation will intensify in the region.

Multi-proxy record of Late Holocene climate events and westerly winds in Maxwell Bay, South Shetland Islands, Antarctica

Glacial expression of climate change during the Holocene was neither uniform geographically nor synchronous in Antarctica, highlighting the influence of regional drivers and local feedbacks on environmental change. Here, we present new data from sediment cores collected in Maxwell Bay, a broad open bay located in the South Shetland Islands, Antarctica. We reconstruct past intervals of glacial marine conditions using diatom assemblage and stable isotope proxy data from the sediment cores. These data suggest that there were episodes of stronger westerly winds in the South Shetland Islands, evidenced by the increased presence of the offshore diatom Fragilariopsis kerguelensis and increased abundance of planktonic foraminifera that are associated with low sea-ice concentration and presence of relatively warm water masses. With an expanded sedimentary archive from the proximal bay, we reconstruct the last 2500 years of environmental conditions in Maxwell Bay and interrogate the record within the context of over a dozen published records in the region. Four major climate intervals are identified: (1) relatively stable, cold climate with high productivity from ∼2500 to ∼1850 calibrated years Before Present (cal yr BP), followed by (2) environmental instability until ∼900 cal yr BP, (3) a prominent Medieval Climatic Anomaly from ∼875 to ∼475 cal yr BP, and (4) cooling during the Little Ice Age between ∼475 and ∼ 60 cal yr BP. More recently, the Antarctic Peninsula experienced rapid regional warming during the second half of the Twentieth Century, followed by a regional reversal since the late 1990s; it is imperative to understand the glacial response to past climate events like this to inform models of future change.

Lithium isotopic evidence for enhanced reverse weathering during the Early Triassic warm period

Elevated temperatures persisted for an anomalously protracted interval following pulsed volcanic carbon release associated with the end-Permian mass extinction, deviating from the expected timescale of climate recovery following a carbon injection event. Here, we present evidence for enhanced reverse weathering-a CO2 source-following the end-Permian mass extinction based on the lithium isotopic composition of marine shales and cherts. We find that the average lithium isotopic composition of Lower Triassic marine shales is significantly elevated relative to that of all other previously measured Phanerozoic marine shales. Notably, the record generated here conflicts with carbonate-based interpretations of the lithium isotopic composition of Early Triassic seawater, forcing a re-evaluation of the existing framework used to interpret lithium isotopes in sedimentary archives. Using a stochastic forward lithium cycle model, we demonstrate that elevated reverse weathering is required to reproduce the lithium isotopic values and trends observed in Lower Triassic marine shales and cherts. Collectively, this work provides direct geochemical evidence for enhanced reverse weathering in the aftermath of Earth's most severe mass extinction.

Tectonic and erosional controls of sediment residence time in small catchments draining an active mountain range: Evidence from uranium comminution age

Sediment residence time (SRT) is a key parameter of the Earth’s surface system, bridging the realms of sediment transport, biogeochemical cycles, sedimentary archives, and watershed management. SRT in mountainous catchments includes the time particles have spent in the subsurface weathering zone, which has been challenging to measure thus limiting our understanding of the magnitude and controlling factors of SRT in steep terrains. In this study, we apply the 234U/238U activity ratio, (234U/238U), which reveals particle comminution age, to estimate SRTs in 32 catchments (drainage area of 6.79–143.67 km2) draining an active mountain range at the eastern margin of the Tibetan Plateau. The uranium comminution age allows us to account for the time that particles have spent in the weathering zone. The sampled catchments span a range of erosional, topographic, climatic and lithologic conditions, providing a unique opportunity to explore the controlling factors on SRTs. We measured the (234U/238U) of the 20–25 µm size fraction of the collected riverbed sediment samples and used the results to calculate particle comminution ages, which are used to approximate SRTs of fine sediment in the catchment. We then investigated the relationships between estimated SRTs and denudation rates, topography, climate, and lithology to assess controls on SRTs. The estimated SRTs range from 5.0 to 149.2 ka, and exhibit strong negative correlations with the 10Be-derived denudation rates and metrics for landscape steepness (relief, gradient, and channel steepness), with weak-to-moderate correlations with climatic and lithologic conditions. By combining the SRTs and denudation rates and assuming a steady-state weathering zone, we estimate a catchment-average comminution depth of 1.98 to 28.7 m, comparable to the depth of weathering zone estimated from modeling studies. Considering a topographic steady-state where denudation rates are in equilibrium with uplift rates, our results suggest that tectonic uplift exerts a primary control on the SRT in active mountain ranges, such that faster uplift rates shorten SRTs. Our findings suggest that tectonic uplift could regulate the temporal duration of chemical weathering by limiting the SRTs of fresh minerals in mountainous regions, sustaining a ‘kinetically-limited’ weathering scenario.

Climate and Human Evolution: Insights from Marine Records.

The relationship between climate and human evolution is complex, and the causal mechanisms remain unknown. Here, we review and synthesize what is currently known about climate forcings on African landscapes, focusing mainly on the last 4 million years. We use information derived from marine sediment archives and data-numerical climate model comparisons and integration. There exists a heterogeneity in pan-African hydroclimate changes, forced by a combination of orbitally paced, low-latitude fluctuations in insolation; polar ice volume changes; tropical sea surface temperature gradients; the Walker circulation; and possibly greenhouse gases. Pan-African vegetation changes do not follow the same pattern, which is suggestive of additional influences, such as CO2 and temperature. We caution against reliance on temporal correlations between global or regional climate, environmental changes, and human evolution and briefly proffer some ideas on how pan-African climate trends could help create novel conceptual frameworks to determine the causal mechanisms of associations between climate/habitat change and hominin evolution.

Cenozoic sedimentary archives of a strike-slip fault zone in the Tanhai Region, Bohai Bay Basin, Northeastern China

The Changdi fault, also known as the Changdi fault zone, is commonly proposed to be a branch of the Tan-Lu fault zone in the Tanhai region of the Bohai Bay Basin. Using three-dimensional seismic data, borehole data, isopach maps, and RMS maps, we attempted to provide a comprehensive understanding of the structural properties and sediment dispersal patterns occurring within the Changdi area from a source-to-sink perspective. Two distinct geomorphological factors were identified in the Changdi area and four types of strike-slip fault-controlled alluvial channels were proposed for the first time. Additionally, three types of sediment dispersal systems, characterized by various sediment infillings, source inputs, and source areas, were reported. The spatial and temporal variations in the geometry and kinematics of the Changdi fault zone were observed to regulate sediment dispersal within the subsag. Sediment dispersal systems in the Changdi area were regulated by sediment dispersal associated with faults resulting from strike-slip movement. The movement of the input port in the provenance area was controlled by strike-slip movements. The movement of the sedimentary center indicated that there was a dextral strike-slip distance of 3.24 km during the E2s3L period. This study suggests that dextral strike-slip movements occurred in the Changdi fault zone, forming a strike-slip fault-controlled basin. The findings of this study may prove useful in developing models to predict the patterns of sediment dispersal controlled by strike-slip faults as well as the location of areas rich in sand.

Cretaceous geology and stratigraphy of Morocco and adjacent coastal basins

The Cretaceous marine sediments of Morocco and adjacent coastal basins provide an outstanding archive of environmental diversity from extended shelf seas and marginal basins along the Atlantic and Tethyan margins to deep oceanic basins of the western Tethys and eastern Atlantic Ocean. The geological highlights of Morocco's fascinating landscape include records of Lower Cretaceous Tethyan marginal and deep-water clastic sequences in the Rif mountain chain (submarine fan systems of the Massylian and Mauretanian flysch units), as well as siliciclastic sedimentary sequences in subsiding coastal basins (TanTan Delta), which extend offshore along the NW African Atlantic margin. Vestiges of the Aptian to Turonian greenhouse climate, sea-level highstands and oceanic anoxic events are exceptionally well preserved in Tethyan marginal and deep-water sedimentary successions of the Rif, in Atlantic coastal basins and as transgressive pulses on the Moroccan Meseta, Sahara platform and High Atlas rift system. Furthermore, sedimentary expressions of the tectonic movements between the African and European plates associated with the end Cretaceous climate and sea-level changes are documented in the Rif mountain chain, in coastal basins, and in the massive marginal marine phosphorite sedimentation in the Middle and High Atlas, on the Moroccan Meseta and Sahara platform. The Cretaceous sedimentary archives from Morocco and adjacent coastal basins still retain untapped potential to further contribute to our understanding of global eustatic sea-level changes and the response of the oceans and marine biota in upwelling driven oxygen minimum zones under greenhouse climate conditions.

A paleoenvironmental and ecological analysis of biomarkers from the Eocene Fossil Basin, Green River Formation, U.S.A.

Exceptionally well-preserved fossil specimens in the Fossil Basin of the Green River Formation (GRF) have made it the subject of extensive paleontological study, but the organic molecular framework that evolved during a key paleoclimatic and fossil-bearing interval during the early Eocene is poorly understood. Whereas the organic geochemistry of the larger co-eval GRF basins has been extensively characterized, our molecular understanding of the fossil-bearing layers in the Fossil Basin and the drivers of the exceptional fossilization therein remain unresolved. To bridge this gap, sediments from the famous 18″-layer — the fossiliferous horizon that is extensively quarried for exceptional soft-tissue fossils — were sampled for organic and isotopic geochemical characterisation. The results show that the Fossil Basin sedimentary archive is geochemically distinct from other GRF basins, as exemplified by the absence of the classical biomarker β-carotane and minimal evidence for the large green algal blooms that predominate in the other GRF lake basins. Photic zone euxinia (PZE), anoxia, and a freshwater cap enabled development of a productive and diverse ecosystem. Salinity and density stratification prevented vertical mixing of the water column and supported preservation of decaying carcasses. In contrast to other GRF basins, the small areal extent and ellipsoid shape of the Fossil Basin focussed terrestrial and freshwater inputs into the lake, resulting in ideal conditions for preservation of an exceptional fossil record.

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.

Paleozoic Equatorial Records of Melting Ice Ages (PERMIA): calibrating the pace of paleotropical environmental and ecological change during Earth's previous icehouse

Abstract. The upper Paleozoic Cutler Group of southern Utah, USA, is a key sedimentary archive for understanding the Earth-life effects of the planet's last pre-Quaternary icehouse–hothouse state change: the Carboniferous–Permian (C–P) transition, between 304 and 290 million years ago. Within the near-paleoequatorial Cutler Group, this transition corresponds to a large-scale aridification trend, loss of aquatic habitats, and ecological shifts toward more terrestrial biota as recorded by its fossil assemblages. However, fundamental questions persist. (1) Did continental drift or shorter-term changes in glacio-eustasy, potentially driven by orbital (Milankovitch) cycles, influence environmental change at near-equatorial latitudes during the C–P climatic transition? (2) What influence did the C–P climatic transition have on the evolution of terrestrial ecosystems and on the diversity and trophic structures of terrestrial vertebrate communities? The Paleozoic Equatorial Records of Melting Ice Ages (PERMIA) project seeks to resolve these issues in part by studying the Elk Ridge no. 1 (ER-1) core, complemented by outcrop studies. This legacy core, collected in 1981 within what is now Bears Ears National Monument, recovered a significant portion of the Hermosa Group and the overlying lower Cutler Group, making it an ideal archive for studying paleoenvironmental change during the C–P transition. As part of this project, the uppermost ∼ 450 m of the core were temporarily transferred from the Austin Core Repository Center to the Continental Scientific Drilling Facility at the University of Minnesota for splitting, imaging, and scanning for geophysical properties and spectrophotometry. Here we (1) review the history of this legacy core, (2) introduce recently obtained geophysical and lithologic datasets based on newly split and imaged core segments to provide a sedimentological and stratigraphic overview of the Elk Ridge no. 1 core that aligns more accurately with the currently recognized regional lithostratigraphic framework, (3) establish the position of the boundary between the lower Cutler beds and the overlying Cedar Mesa Sandstone in the core, and (4) outline our ongoing research goals for the core. In-progress work on the core aims to refine biostratigraphic and chemostratigraphic age constraints, retrieve the polarity stratigraphy, interrogate preserved cyclostratigraphy, analyze sedimentary structures and paleosol facies, investigate stable isotope geochemistry, and evaluate elemental abundance data from X-ray fluorescence (XRF) scanning. Together with outcrop studies throughout Bears Ears National Monument and its vicinity, these cores will allow the rich paleontological and paleoenvironmental archives recorded in the continental Carboniferous–Permian transition of western North America to be confidently placed in a robust chronologic context that will help test hypotheses relating ecosystem evolution to the Carboniferous rainforest collapse, initial decline of the Late Paleozoic Ice Age, and long-wavelength astronomical cycles pacing global environmental change.