Pleistocene Deposits Research Articles

Peculiarities of clay minerals formation in the Pleistocene sediments under specific tectonomagmatic and hydrothermal conditions of the Central Hill (Escanaba Trough, Gorda Ridge, Pacific Ocean). Communication 1. Hole ODP 1038B

Using a complex of analytical methods, clay minerals were studied in Pleistocene sediments from Hole ODP 1038B, 120.50 m deep, drilled on the northwestern edge of the Central Hill, located in the Escanaba Trough (Gorda Ridge) near a hydrothermal source with a temperature of 108°C, as well as in Pleistocene background terrigenous sediments from reference Hole ODP 1037B, drilled in the Escanaba Trough, 5 km south of Central Hill. The association of terrigenous clay minerals in sediments from Hole 1037B consists of mixed-layer smectite-illites, smectite, chlorite, illite, and kaolinite. In sediments from Hole 1038B in the interval from the bottom surface to a depth of 5–7 m, clay minerals are terrigenous. In the rest of the sedimentary section, clay minerals are represented by newly formed biotite, chlorite, and dioctahedral smectite. Their formation occurred under the conditions that arose during the intrusion of basaltic melt into the Escanaba trough with the formation of a laccolith and the subsequent rapid cooling of its flank; the intrusion was accompanied by the ascent of high-temperature hydrothermal fluid in the central discharge channel, interacting with the adjacent sediments. As a result, at the high-temperature stage of this interaction, finely dispersed biotite was formed in the sediments due to the original terrigenous clay minerals, K-feldspar and amphiboles. Then, at the rapid cooling of the hydrothermal fluid to a temperature presumably 270–330°C, partial replacement of biotite by chlorite. With further rapid cooling of the hydrothermal fluid to a temperature of 200°C and below and its mixing with sea water seeping into the sediments of the Central Hill, smectite was formed.

Peculiarities of Clay Mineral Formation in Pleistocene Sediments Under Specific Tectonomagmatic and Hydrothermal Conditions of the Central Hill (Escanaba Trough, Gorda Ridge, Pacific Ocean): Communication 2. Holes ODP 1038A and 1038H

Peculiarities of Clay Mineral Formation in Pleistocene Sediments Under Specific Tectonomagmatic and Hydrothermal Conditions of the Central Hill (Escanaba Trough, Gorda Ridge, Pacific Ocean): Communication 2. Holes ODP 1038A and 1038H

Comparative Analysis of Geochemical Peculiarities of Pleistocene Sediments in the Indian and Atlantic Oceans

Comparative Analysis of Geochemical Peculiarities of Pleistocene Sediments in the Indian and Atlantic Oceans

Topographic ridges express late Quaternary faulting peripheral to the New Madrid seismic zone, intraplate USA: Their tectonic implications

Northeast-trending linear topographic ridges in Pliocene and Quaternary sediments adjacent to the New Madrid seismic zone (NMSZ), intraplate North America, have been long speculated to be neotectonic landforms related to reactivation of basement faults of the eastern Mississippi Valley Rift margin. Earthquake epicenters and paleoseismological studies show that eastern rift margin faults (ERMF) were active during late Quaternary south of a restraining bend in the Mississippi Valley Rift fault complex, but the ERMF zone north of the restraining bend (ERM-N) and underlying the linear ridges is seismically quiescent. A previous P-wave seismic reflection survey across the most prominent linear ridge (Rives lineament) revealed that it overlies a horst in Eocene sediment. To ascertain whether the Rives lineament could have been produced by surface faulting/folding, we collected electrical resistivity tomography (ERT) and ground penetrating radar (GPR) profiles to image the ridge's shallow subsurface features. We interpret shallow folding and faulting of late Pleistocene sediment in our ERT and GPR images. Additionally, convexity of multiple topographic profiles of scarps along margins of the Rives lineament was quantified and compared to the convexity of profiles of known neotectonic scarps and of fluvial terrace riser profiles within the region. Comparison of these profiles reveals a high degree of similarity between the scarps along the Rives lineament margins and the Holocene Reelfoot thrust scarp. When combined, our results strongly suggest late Pleistocene or Holocene folding and faulting created this ridge despite its current seismic quiescence, and thus they provide useful insight for assessing the seismic hazard potential of quiescent faults in strike-slip systems in general. We conclude that the late Quaternary series of movements documented on the Reelfoot thrust was initiated to accommodate crustal shortening after transpressional fault movements on the ERM-N became inactive in late Pleistocene or early Holocene and that movement along the ERM-N may resume if the Reelfoot thrust has an interval of inactivity in the future. Our results suggest how fault interactions within a strike-slip system can change, making faults with significant amounts of seismic potential appear as though they are inactive.

Timing and geometry of the Chemehuevi Formation reveal a late Pleistocene sediment pulse into the Lower Colorado River

The Chemehuevi Formation is a distinctive 50−150-m-thick wedge-shaped Pleistocene sedimentary unit deposited by the Colorado River. It lines the perimeters of the river’s floodplains and bedrock canyons for more than 600 km between the mouth of the Grand Canyon and the delta region in the Gulf of California. The formation is composed of a basal tan to light-yellowish-brown and pale-orange mud-dominated facies overlain and interbedded by a light-yellow-brown sand-dominated facies. The unit is one of two extensively exposed aggradational packages in the Lower Colorado River corridor, in addition to a series of other smaller alluvial terrace deposits. The Chemehuevi Formation appears to represent the response of a fully integrated Colorado River system to a significant perturbation, in contrast to the Bullhead Alluvium, which is likely a unique result of Pliocene river integration. The aggradation of the Chemehuevi Formation in the Lower Colorado River corridor may be similarly due to a unique event in the Colorado River system, or it may instead be a well-preserved sedimentary sequence recording typical behavior of the Colorado River below the Grand Canyon in the late Pleistocene. As such, multiple causal mechanisms have been proposed, but no study to date has conclusively explained the Chemehuevi Formation. To help resolve its timing, duration, and origin, we applied post-infrared infrared stimulated luminescence, carbonate U-Th series, and zircon sensitive high-resolution ion microprobe U-Th series geochronology to determine the ages of key exposures of the unit over a wide spatial area. These new data demonstrate that the Chemehuevi Formation was deposited ca. 110−90 ka. The depositional ages collectively overlap, suggesting that deposition occurred rapidly relative to the resolution of the geochronometers. The new depositional timing coincides with a shift from glacial to interglacial conditions after the marine isotope stage 5-6 transition. This observation is consistent with a climate-induced sediment pulse as a causal mechanism, yet correlations with similar deposits in the Colorado River headwaters or in neighboring catchments appear elusive. Potentially, climate transitions between glacial and interglacial periods induced a sediment pulse from hillslopes of the Colorado River system that resulted in the Chemehuevi Formation. An alternative or additional explanation is that the Chemehuevi Formation represents release of lava dam−impounded sediment in the Grand Canyon. The surface geometry of the Chemehuevi Formation projects upstream to the approximate location of lava dams, and the largest possible lava dam impoundment (the Upper Prospect dam) is comparable in volume to the formation. The lava dam hypothesis appears to be a possible explanation for the Chemehuevi Formation. However, tying deposition to a specific lava dam or series of lava dams remains challenging due to discrepancies in timing and volume. The combined effects of a series of lava dams may have led to the Chemehuevi Formation, as the last Pleistocene lava dam eruption coincides with the onset of deposition. Alternatively, the formation may result from the combined effects of both regional climate transitions and the lava dams that created a transient reservoir to compound a climate transition−driven sediment pulse. The geochronologic data presented here do not allow us to distinguish between the lava dam or climate transition hypotheses but will need to be reconciled with any future proposed depositional model.

First record of terrestrial vertebrates from a Late Pliocene-Early Pleistocene deposit in Cuba

Here we report new land vertebrate fossils from the El Abra outcrop in Matanzas, Western Cuba, offering key insights into the Late Pliocene-Early Pleistocene Greater Antillean mammal fossil record. The paucity of documented terrestrial mammal fossils in this interval has hindered a more comprehensive understanding of their evolutionary histories. The discovery of previously undocumented capromyine rodent dental remains provides a significant enrichment to the Cuban land vertebrate fossil record. One notable specimen, a capromyine molar, displays an occlusal pattern characteristic of genera such as Mesocapromys, Mysateles, Macrocapromys, Capromys, and Geocapromys, as well as the Hispaniolan Hexolobodon. While these genera form a monophyletic clade that radiated during the Pliocene-Pleistocene, typically marked by molars with open roots, the El Abra specimen shows partially closed roots, a feature not previously observed in Cuban taxa, suggesting potential affinities with Hexolobodon. Other incertae sedis mammals are represented by fragmentary long bone diaphyses with evidence of transportation. Microfossil assemblages indicate reworking, with taxa spanning from the Late Cretaceous to the earliest Pleistocene. Preliminary foraminiferal biostratigraphy and 87Sr/86Sr isotope analysis support a depositional age between the latest Pliocene and earliest Pleistocene. However, while the exact age of these new terrestrial vertebrate fossils remain uncertain for lack of direct, absolute dating, we approximate their age based on the estimated chronology. These fossils are likely diachronic and could be potentially older. These findings suggest complex patterns of vertebrate dispersal and diversification in the Caribbean. The findings highlight complex biogeographic patterns of vertebrate dispersal and diversification across the Caribbean. Addressing these historical biodiversity patterns is critical, as the combination of recent extinctions and gaps in the fossil record may obscure a true understanding of past species richness and evolutionary processes within the insular Caribbean.ResumenAquí reportamos nuevos fósiles de vertebrados terrestres del afloramiento El Abra en Matanzas, Cuba occidental, que ofrecen relevante información sobre el registro fósil de mamíferos de las Antillas Mayores durante el Plioceno Tardío-Pleistoceno Temprano. La escasez de fósiles documentados de mamíferos terrestres en este intervalo ha obstaculizado una comprensión más completa de sus historias evolutivas y diversidad. El descubrimiento de restos dentales previamente no documentados de roedores representa un enriquecimiento del registro fósil de vertebrados terrestres de Cuba. Un espécimen notable, un molar de capromyinae, exhibe un patrón oclusal característico de géneros como Mesocapromys, Mysateles, Macrocapromys, Capromys y Geocapromys, así como del género Hexolobodon de La Española. Si bien estos géneros forman un clado monofilético que radiaba durante el Plioceno-Pleistoceno, típicamente caracterizado por molares con raíces abiertas, el espécimen de El Abra muestra raíces parcialmente cerradas, una característica no observada previamente en los taxones cubanos, lo que sugiere afinidades potenciales con Hexolobodon. Otros mamíferos, incertae sedis, están representados por fragmentos diafisarios de huesos largos con evidencia de transporte. Las asociaciones de microfósiles indican retrabajo y mezcla, ya que hay taxones que abarcan desde el Cretácico Tardío hasta el Pleistoceno Temprano. La bioestratigrafía preliminar de foraminíferos y el análisis de isótopos de estroncio (87Sr/86Sr) apoyan una edad de depósito entre el Plioceno muy tardío y el Pleistoceno Temprano. Sin embargo, la edad exacta de estos vertebrados terrestres sigue siendo ambigua por carecer de fechados directos, por lo que aproximamos su antigüedad basándonos en la cronología estimada del depósito. Estos fósiles son también probablemente diacrónicos y podrían ser potencialmente más antiguos. Estos hallazgos sugieren patrones complejos de dispersión y diversificación de vertebrados en el Caribe. Abordar estos patrones históricos de biodiversidad es fundamental, ya que la combinación de extinciones recientes y vacíos en el registro fósil puede oscurecer una comprensión completa de la riqueza de especies pasadas y los procesos evolutivos en el Caribe insular.

Spatial distribution and deposits of cliffs along the Brazilian semi-arid coast

Cliffed coasts are common landforms found worldwide, but their precise spatial distribution and the nature of associated deposits may present regional gaps. This works presents a geological and geomorphological study of the Brazilian semi-arid coast (∼900 km), which was carried out on coastal cliffs with the aim of addressing three important knowledge gaps: i) spatial distribution of coastal cliffs, analyzed using topographic data from SRTM, LiDAR and field surveys, ii) the lithology and ages of the deposits, investigated through sedimentological analysis and OSL dating, and iii) origin of the cliffs, explored through relations with global and regional sea-level curves. The supply of terrigenous sediments to the western equatorial Atlantic coast was also considered. Coastal cliffs were identified along 235 km of the coastline, represented mainly by inactive cliffs (∼170 km). These cliffed coasts are composed mainly by poorly sorted siliciclastic sandstones and conglomerates, deposited in the Late Pleistocene. The depositional phases correlate with abrupt climate changes, due to pulses of terrigenous supply to the continental margin during the Heinrich Events. The formation of marine cliffs in these deposits occurred in the mid-Holocene, as sea level reached current elevation (msl) in ∼7 ka and 2-4 m above in ∼5.5 ka. This previous higher sea-level supports the widespread occurrence of inactive cliffs. The findings in this work contribute to i) improved mapping of coastal landforms, with higher resolution data demonstrating that previous works underestimated the presence of coastal cliffs; ii) the coastal cliffs are cut in Pleistocene sediments instead of older, Miocene deposits of the Barreiras Formation as previously assumed; iii) cliff formation due to marine erosion occurred in the mid- to- late Holocene; iv) the siliciclastic sediments that compose the cliffs are correlatable to marine sediments found in adjacent offshore areas, highlighting the role of abrupt global climatic changes in the Pleistocene in shaping contemporary coastal landscapes.

Methodological Issues in Pollen Analysis of Pleistocene Deposits in Denisova Cave

Denisova Cave, in the northwestern Altai, is a key Paleolithic complex in North Asia. Pleistocene deposits in the cave contain lithic industries and human fossils documenting the evolution of the cultural traditions of Denisovans in the second half of the Middle and in the Upper Pleistocene. This study addresses methodological issues in paleogeographic interpretation of pollen records relating to Quaternary deposits of cave sites. We present the results of the analysis of recent and subrecent spectra of cave sediments and soil samples taken at sites of characteristic plant communities in natural zones of the Anui River valley near Denisova Cave. Findin gs from taphonomic study of pollen microremains from loose sediments in the East Chamber of the cave make it possible to obtain a correct climato-stratigraphic and climato-phytocenotic interpretation of pollen spectra from Pleistocene deposits in Denisova Cave.

Fingerprint of Plio–Quaternary detrital zircon geochronology: Implications for sediment provenances and geomorphological evolution of the Yangtze Delta

The Yangtze (Changjiang River) Delta serves as a prominent depocenter for siliciclastic sediments from the Tibetan Plateau and Yangtze Craton, providing essential data on sediment source-to-sink dynamics and geomorphological evolution of large river drainage systems. This study presents the detrital zircon geochronology of Plio–Pleistocene sediments in the Yangtze Delta, alongside the data from modern river sediments, to elucidate provenance evolution since the Pliocene. The zircon geochronology reveals a considerable shift in sediment provenance during the Pliocene–Pleistocene transition. The Pliocene sediments exhibit a straightforward and predominant zircon age spectrum characterized by a typical peak age of 100–200 Ma. This spectrum markedly differs from the modern upper–middle Yangtze River sediments but closely resembles those of local rivers in the lower Yangtze River region. This demonstrates that the Pliocene sediments originated from local mountainous rivers, indicating the paleo-Yangtze River channelization prior to the Quaternary. In contrast, the zircon age spectra of Pleistocene sediments in the present-day delta reveal several dominant age groups ranging from 11.9 ± 1 to 3643 ± 30 Ma, similar to those found in present-day upper–middle Yangtze River sediments. This implies that the Pleistocene sediments were mainly derived from the upper–middle Yangtze River, showing a diversity of source rocks with varying geological ages and origins. The presence of the upper Yangtze River provenance signal, characterized by Cenozoic (<65 Ma) zircons, in early Pleistocene strata (ca. 1.6 Ma) of the delta suggests that the paleo-Yangtze River transported Tibet-sourced sediments into the modern delta area no later than that time. These findings indicate the geomorphological evolution of the Yangtze River Delta from an intermontane basin in the Pliocene to an alluvial–fluvial plain during the Quaternary. This geomorphological and geographic evolution, along with changes in sediment source, directly reflect extensive tectonic subsidence in eastern China since the late Cenozoic.

Structural style & kinematic analysis of deformation in the northern Dezful Embayment, Zagros Fold-Thrust Belt, SW Iran

A comprehensive understanding of structure and kinematic characteristics of fold and thrust belts provides significant information for hydrocarbon exploration and production. The kinematic evolution and structural style of three subsurface oilfields, Zeloi, Lali and Karun, in the northern part of the Dezful Embayment, a significant petroleum province of the Zagros Fold-Thrust Belt in SW Iran, were investigated using 2D seismic data. Interpretation of the 2D seismic profiles with up to 5 km depth consisting of upper Jurassic to Pleistocene sediments and the balanced cross-sections constructed revealed diverse geometries and kinematics along the oilfields. These results demonstrate that the structural style of the oilfields was controlled by the Gachsaran and Dashtak formations as upper and middle detachment levels, respectively. Tear faults affected the along-strike variations in structural style of the oilfields. Based on the analysis of growth strata, folding evolved as limbs rotated and hinges migrated, beginning in the mid-Miocene. During the later stages of deformation, the initial detachment folds transformed into fault-bend folds.

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.

Geochemical fingerprints of early diagenesis in shallow-water marine carbonates: Insights from paired δ44/40Ca and δ26Mg values

We present a suite of major element stable isotope (δ13C, δ18O, δ44/40Ca, δ26Mg), and selected trace element (Sr/Ca and Mg/Ca) data from Pleistocene sediments from the Great Barrier Reef (IODP Expedition 325), as well as Holocene surface sediments from the Bahamas (Triple Goose Creek, Andros Island) to identify geochemical fingerprints associated with early marine and meteoric diagenesis. Sediments from both sites exhibit co-variation in δ13C and δ18O values, depletion in trace elements, and distinct geochemical trends in δ26Mg and δ44/40Ca values that reflect differences between diagenetic alteration in marine and meteoric fluids. While marine diagenesis results in lower Sr/Ca ratios, higher δ44/40Ca values, and little effect on bulk sediment δ26Mg values, meteoric diagenesis leads to lower Sr/Ca ratios, lower δ44/40Ca values, and lower δ26Mg values. Using a numerical model of diagenesis, we show how diagenetic alteration by meteoric fluids must occur after an initial period of diagenetic alteration by marine fluids, a two-stepped diagenetic history that complicates the interpretation of geochemical data in meteorically altered marine carbonate sediments. Finally, we discuss how paired metal isotopes may serve as a robust indicator of meteoric alteration in ancient shallow-water marine carbonate sediments.

Body mass estimation of the extinct South American native ungulate Neolicaphrium recens Frenguelli, 1921 (Litopterna, Proterotheriidae): testing classical predictive models

ABSTRACT Neolicaphrium recens (Mammalia, Litopterna) was a slender South American Native Ungulate (SANU). The assessment of its body size is a big challenge because there are no living representatives and no clear close morphological analogues. In this contribution, we report for the first time a femur of N. recens exhumed from Late Pleistocene sediments of Uruguay, improving the knowledge of the postcranial skeleton of the species. This stylopodial element is important for doing palaeobiological inferences, including estimating the body mass. We performed body mass estimations by previous allometric equations. As a method to directly test the models and their usefulness in fossils, we applied the equations on six specimens of extant deers of known body weight and with skeletons preserved. According to the obtained data, the transverse width at the middle of the diaphysis and the circumference of the bone at that level can be used with confidence to estimate the body mass of fossil ungulates. We point out a set of more probable values of body mass for N. recens: 28.76298 ± 10.6412, 27.78496 ± 8.0576, and 26.72 ± 10.42 kg. Morphological variables as well as the models for estimating body masses in fossils are widely discussed.

Changes in the Composition of Upper Pleistocene Sediments in the Center of an Active Hydrothermal System (Middle Valley, Juan De Fuca Ridge, Pacific Ocean)

Changes in the Composition of Upper Pleistocene Sediments in the Center of an Active Hydrothermal System (Middle Valley, Juan De Fuca Ridge, Pacific Ocean)

First results of comparative analysis of Pleistocene sediments chemical composition from the Indian and Atlantic oceans

First results of comparative analysis of Pleistocene sediments chemical composition from the Indian and Atlantic oceans

Large variability and 2H-depletion of Middle Miocene to Pleistocene alkenone hydrogen isotopes in the Equatorial Pacific reflect subsurface, low light haptophyte growth

Hydrogen isotope ratios of haptophyte derived long-chain alkenones (δ2HC37:2) have shown to be a useful tool for reconstructing past isotopic compositions of surface seawater (δ2HSSW). The δ2HSSW is related to global ice volume, sea surface salinity and the local hydrological cycle. Here, we present a hydrogen isotope record of alkenones spanning the last 14.5 Ma from IODP site U1338 in the east equatorial Pacific. The alkenone-based reconstructed δ2HSSW is substantially more negative and variable than reconstructed δ2HSSW based on published oxygen isotopes of coccolith carbonates. This suggests that factors other than the isotopic composition of seawater affect the hydrogen isotopic composition of alkenones. The relatively negative and highly variable δ2HC37:2 values are in line with published modern observations on alkenones from suspended particulate matter in the equatorial and north Pacific, with the highest values at relatively high light conditions at the surface and the lowest values at higher water depth and relatively low light conditions. This suggests that the relatively negative and highly variable δ2HC37:2 values in these Middle Miocene to Pleistocene sediments are likely derived from haptophytes growing below the sea surface under variable low light conditions. In regions where the contribution of alkenones from subsurface production, due to high subsurface nutrients, at low light intensities to the sediment is relatively high the δ2HC37:2 has to be interpreted with care as a proxy for δ2HSSW.

Constraining the evolutionary stages of a hypogene karst system by combining morphological, geochemical and geochronological data - the example of carbonate breccia-hosted Melnička Peštera

A combination of morphological observations, geochemical data from calcite minerals and geochronology by burial age dating and U-series is used to constrain the geological and geomorphological setting and the evolutionary stages of a hypogene karst system. This methodological suit is applied to Melnička Peštera, a horizontal cave developed in carbonate breccia overlying dolomite marble in Melnica locality (N. Macedonia), where hydrothermal karst development occurred in both dolomite and calcite marble. The passage morphology of the cave, having a reverse triangle, Laughöhle cross-sections, suggests development near the water table by slowly moving waters. Calcite crusts are found throughout the cave, and based on their relationship to passage morphology, appear to pre-date main horizontal passage formation. Their carbonate stable and clumped isotope and fluid inclusion noble gas compositions indicate cooling of the hydrothermal system with an increased contribution of shallower groundwater. U-series data suggests Early Pleistocene deposition of the calcite crusts. Water table notches and convectional features carved into breccia bedrock and calcite crusts point to subsequent development at and above the water table by condensation corrosion. The solutional aggressiveness near the water table was likely related to CO2, that previously degassed from the deeper parts of the system where calcite was depositing, and redissolved in the cooler, shallower waters. Due to poor connection with the surface, the cave air above the water table likely had high pCO2, that further helped to maintain aggressiveness of the groundwater at the water-air contact, and boosted condensation corrosion above it, preventing deposition of related secondary calcite minerals. The cave-hosting carbonate breccia deposited as an alluvial fan filling up a paleovalley cut into Upper Miocene sediments. Cosmogenic nuclide burial age dating of quartz fragments confirms Early Pliocene age for the breccia, and constrains the paleovalley incision to Late Miocene, likely related to base level lowering caused by the Messinian Salinity Crisis.

The first confirmation of North American extinct shrub-ox (Euceratherium, Artiodactyla, Mammalia) in the Early Pleistocene of northern China

Euceratherium is a genus generally considered to represent an Ovibovine member of the Caprini, and up to date considered to occur only in North America. Here, we describe two species of Euceratherium discovered from the Early Pleistocene deposits in northern China, E. collinum and Euceratherium sp., the first confirmed record of Euceratherium in Eurasia and outside North America. The earlier age of Chinese Euceratherium than that of its North American counterpart indicates that Euceratherium might originate from East Asia and spread into North America later. The phylogenetic analysis based on the North American and our Euceratherium collinum materials indicates its closer relationship to Ovibos moschatus than the other bovids. Ecomorphological analysis based on the teeth and metapodials of Euceratherium sp. from Xinyaozi suggests that the Chinese species has the same paleodiet and paleohabitat preferences as those of its North American counterpart. By broadening our study from Euceratherium to its upper taxonomic group, the Quaternary Ovibovine, we found that the latter probably originated from a Kabulicornis-like form and could be divided into two groups in the Late Pliocene, “alticornis” and “depressicornis”. These two groups evolved in Eurasia in the Early Pleistocene. They might disperse from Eurasia to North America twice, in the late Early Pleistocene and the late Middle Pleistocene, respectively.

Geochemical peculiarities of the Atlantic Pleistocene sediments

In the geochemical review based on records from cruises of International project of Deep-Sea Drilling (phases of DSDP, ODP, IODP) and other literature data we presented tables of average arithmetic chemical composition, meanweighted chemical composition, accumulation rates, and mass accumulation rates of chemical components. These tables can be used for comparative analysis with sediments of the same or other stratons in different oceanic basins and also with paleooceanic sediments on the continents. Terrigenous matrix dominates within lithogenic matter. Using methods of mathematical statistics we revealed main geochemical associations and base factors determinating the chemical composition of studied sediments. Masses of oxides of petrogenic elements and a number of trace elements have been calculated for Pleistocene sediments. We managed to take an idea about average chemical composition of the Atlantic Pleistocene.

Element composition of several marine macrophytes (Crimea, Black Sea) and correlations with the element abundances in sediments and seawater

The study of the element accumulation in marine plants against the backdrop of permanently increasing environmental pollution is of particular importance due to the participation of these plants in biogeochemical cycles. The element abundances are highly variable and depend on both the macrophyte species and environment. The purpose of this study was to analyze the elemental composition of widespread marine plants of different taxonomic affiliations collected in the same area of the Black Sea coast. The contents of 74 elements in three species of lower (red, brown, green algae) and one species of higher plants (seagrass) were analyzed using inductively coupled plasma mass spectrometry. High contents of most elements were found in the red alga Ceramium ciliatum and in rhizomes of the seagrass Zostera noltei. In C. ciliatum, high metal bioaccumulation factors were found, which are dependent also on their concentration in the environment. Compared to the higher plant, all the macroalgae accumulated increased amounts of As and I. The seagrass proved to be a good concentrator of Mo and Sb, and relatively high contents of Mn, Co, Ni, Zn, Cd and Ir were registered in its leaves. High contents of Mg, S, Ge, Se and Ta were found in the green alga Ulva rigida, and elevated levels of Al, As, Sr, Zr, Ru, Rh, Pd, Ag, Ba and Re were noted in the brown alga Gongolaria barbata. The enrichment factors for most elements in the sediments were well above 1 with respect to both the local Late Pleistocene sediments and the upper continental crust. The strength of correlations between the element contents in the plants and sediments was found to decrease with the specific surface area growth and appeared to have a lower asymptotic limit of the sediments–seawater correlation strength.