Pleistocene Deposits Research Articles

Eptesicus nilssonii varangus subsp. nov. (Vespertilionidae, Chiroptera) from the Lower Pleistocene of the Taurida Cave in Crimea.

A new northern serotine bat Eptesicus nilssonii varangus subsp. nov. is described on the base of an incomplete skull and a mandibular fragment from the Lower Pleistocene deposits of the Taurida cave in the central Crimea. This is the earliest record of the species. The presence of E. nilssonii (Keyserling et Blasius, 1839) in the Early Pleistocene bat assemblage of the Taurida cave indicates that this species lived in the south of Eastern Europe before its spreading into Central and Southeastern Europe.

RESULTS OF STUDYING THE PLEISTOCENE IN THE VILGORT SECTION (CHERDYN DISTRICT, PERM TERRITORY)

Link for citation: Plyusnin A.V., Sulima A.I., Marinov V.A., Vdovichenko S.I., SamodurovS.A. Results of studying the Pleistocene in the Vilgort section (Cherdyn district, Perm territory). Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.148-158.In Rus. The relevance. The study of glacial deposits, which is one of the main components of most continental sedimentary formations of all ages, makes it possible to identify the features of its structure and formation, as well as to establish the facies-genetic confinement. This is especially true for Quaternary geology, since makes it possible to carry out stratigraphic comparisons and identify paleogeographic settings for the formation of deposits. This paper presents the results of a comprehensive lithological and biostratigraphic study of the Vilgort section of the Kolva river valley, Cherdyn district of the Perm Territory. The main aim of the research is to study the geological section and substantiation of the age of the Mesozoic deposits according to the fauna complex. Objects: continental deposits of the Middle Pleistocene, exposed in the right side of the river Kolva. The deposits of this region are poorly studied. References are sown in the literature about the Mesozoic fauna found in the Vilgort section. Methods: geomapping, layered lithological description, layer-by-layer sampling, biostratigraphic studies. Results. These studies made it possible to carry out a detailed layer-by-layer description and stratigraphic subdivision of the Vilgort section. The Permian carbonate deposits are overlain by eluvial-deluvial deposits of the Likhvin horizon, they are overlain first by lacustrine-glacial, and then by glacial deposits of the Dnieper horizon of the middle Pleistocene with erratic blocks of Mesozoic repeatedly redeposited terrigenous rocks. Due to the neotectonic activity of the right-bank block part of the Vilgort area, which underwent uplift in the Late Pleistocene, most of the Upper Pleistocene deposits were eroded, which explains the stratigraphic unconformity, when modern deposits lie on glacial deposits of the Middle Pleistocene. According to the results of micropaleontological studies, foraminifers were identified from samples taken in the fifth layer: the Middle Volgian substage of the Volgian stage (sample 1); distributed in the interval of the Ryazanian Stage of the Lower Cretaceous (sample 3) and the middle and upper substages of the Volgian Stage (sample 4).

Palynological characteristics of plant communities in the eastern Arctic during the Early to Middle Calabrian Age

Palynological analysis of Early Pleistocene sediments from Lake El'gygytgyn indicate that climate was warmer than present between c. 1.2860 and 1.6975 Ma (late Gelisian–early Calabrian ages), although variations in the paleovegetation indicate fluctuations between relatively cool and warm conditions. During the coolest intervals, the vegetation on the Anadyr Plateau was a mix of Betula-Salix shrub tundra and Larix forest-tundra. Larix forests, which probably included trees species of Betula and Alnus, characterized the regional vegetation during the warmest times. Slightly cooler interglaciations are indicated by the presence of Larix-forest tundra. Pinus pumila pollen is not consistently present in all interglaciations, indicating that variations in the extent and/or duration of snow cover occurred during these warm intervals. The absence of pollen from this evergreen shrub contrasts with Holocene and Late Pleistocene assemblages, where the taxon is a hallmark of warm conditions. During the Early Pleistocene, Betula pollen indicates the plant's presence during warm and cool intervals, in contrast to Late and Middle Pleistocene spectra where shrub Betula is absent or rare. The pollen data from MIS 55 suggest that it was the coolest of the Pleistocene “super” interglaciations and that the MIS 43 climate was as warm as that of MIS 55. The El'gygytgyn palynological record is a powerful reminder that the distribution of arctic communities can be vastly reduced or eradicated during warm Earth scenarios.

Western visitors at the Blätterhöhle (city of Hagen, southern Westphalia) during the Younger Dryas? A new final palaeolithic assemblage type in western Germany.

Until now, it was considered certain that the last reindeer hunters of the Ahrensburgian (tanged point groups) existed exclusively in northwestern Central Europe during the Younger Dryas Cold Period (~ Greenland Stadial 1). The excavations carried out since 2006 on the forecourt (Vorplatz) of the small Blätterhöhle in Hagen on the northern edge of the Sauerland uplands of southern Westphalia (North Rhine-Westphalia, western Germany) have now changed this view. Beneath a surprisingly extensive sequence of Mesolithic find horizons, Pleistocene sediments could be reached whose excavations yielded a Final Palaeolithic lithic ensemble of the Younger Dryas, unusual for the region and beyond. It is characterised by numerous backed lithic projectile points of high variability. Comparisons suggest a typological-technological connection with the Western European Laborian / Late Laborian. Neither in the nearer nor in the wider surroundings has a comparable lithic find ensemble been found so far. In addition, there is a lack of clear evidence for the reindeer in the fauna. Surprisingly, the vast majority of radiocarbon dates of bones and charcoals from the investigated archaeological horizon of the Final Pleistocene proved to be significantly older than expected from their stratigraphic position. This phenomenon has not yet been clarified.

Hydrogeochemical evaluation, groundwater contamination and associated health risk in southern Tangail, Bangladesh

Water pollution is a worldwide concern that has growing severe in developed and developing nations. Increasing groundwater pollution threatening both the physical and environmental health of billions of people as well as economic progress. Consequently, hydrogeochemistry, water quality and potential health risk assessment is crucial for water resource management. The study area comprises Jamuna Floodplain (Holocene deposit) area in the west and the Madhupur tract (Pleistocene deposit) area in the eastern part. Total 39 groundwater samples were collected from the study area and were analyzed for physicochemical parameters, hydrogeochemical, trace metals, and isotopic composition. The water types are mainly Ca–HCO3- to Na–HCO3- types. The isotopic compositions (δ18O‰ and δ2H‰) analysis traces the recent recharge in Floodplain area from rainwater and no recent recharge in Madhupur tract. The concentration of NO3−, As, Cr, Ni, Pb, Fe, and Mn in shallow and intermediate aquifer at the Floodplain area exceed the WHO-2011 permissible limit and is lower at deep Holocene and Madhupur tract aquifer. The integrated weighted water quality index (IWQI) exposed groundwater from shallow and intermediate aquifer are unsuitable for drinking and deep Holocene aquifer and Madhupur tract are suitable for drinking purposes. PCA analysis confirmed that anthropogenic activity is dominant in shallow and intermediate aquifers. The non-carcinogenic and carcinogenic risk for adults and children is due to oral and dermal exposure. The non-carcinogenic risk evaluation revealed that the mean hazard index (HI) values range from 0.009742 to 16.37 for adults and 0.0124–20.83 for children, respectively, and most groundwater samples from shallow and intermediate aquifers exceed the permissible limit (HI>1). The carcinogenic risk ranges from 2.71 × 10−6-0.014 for adults and 3.44 × 10−6-0.017 for children via oral consumption and 7.09 × 10−11-1.18 × 10−6 for adults and 1.25 × 10−10-2.09 × 10−6 for children via dermal exposure. Spatial distribution shows the presence of trace metal and associated health risk is high in shallow and intermediate aquifer (Holocene) than in the deep (Holocene) Madhupur tract (Pleistocene). The study implies that effective water management will ensure safe drinking water for the future generation of people.

<i>EPTESICUS NILSSONII VARANGUS</i> SUBSP. NOV. (VESPERTILIONIDAE, CHIROPTERA) FROM THE LOWER PLEISTOCENE OF THE TAURIDA CAVE IN CRIMEA

A new northern serotine bat Eptesicus nilssonii varangus subsp. nov. is described on the base of an incomplete skull and a mandibular fragment from the Lower Pleistocene deposits of the Taurida cave in the central Crimea. This is the earliest record of the species. The presence of E. nilssonii (Keyserling et Blasius, 1839) in the Early Pleistocene bat assemblage of the Taurida cave indicates that this species lived in the south of Eastern Europe before its spreading into Central and Southeastern Europe.

Dire wolf (Canis dirus) from the late Pleistocene of southern Canada (Medicine Hat, Alberta)

ABSTRACTThe dire wolf (Canis dirus) had a broad geographic range in Pleistocene North and South America. Its northernmost occurrence has been reported from late Pleistocene deposits in Medicine Hat, Alberta, representing the only record of the taxon in Canada. However, the dentary upon which these reports were based has never been described or illustrated. The Medicine Hat specimen is badly crushed and appears to be from an old individual, which precludes the observation of adult diagnostic morphological characters. Geometric morphometrics were used to test the previous identification of the Medicine Hat dentary. A landmark‐based principal component analysis and a canonical variates analysis suggests that the specimen more strongly resembles dire wolf specimens than grey wolf (Canis lupus). Identification of the Medicine Hat specimen as C. dirus supports it as the northernmost occurrence of this species in North America. However, we note the potential for allometric relationships that may confound differentiation between grey and dire wolves based on the morphology of the dentary. This study concludes by identifying future work needed in the areas of canid allometry and the biogeography of late Pleistocene North America and Beringia.

Petrology of Bengal Fan turbidites (IODP Expeditions 353 and 354): provenance versus diagenetic control

ABSTRACT High-resolution petrographic and heavy-mineral analyses of Bengal Fan turbidites from six cores drilled during IODP Expeditions 353 and 354 elucidate factors controlling their intersample compositional variability as a key to understanding sedimentary processes and erosional evolution of the Himalayan belt since the Miocene. Bengal Fan turbidites are feldspatho-quartzose to litho-feldspatho-quartzose with plagioclase > K-feldspar; slow-settling micas increase in abundance in very fine sand and coarse silt. The feldspar/quartz ratio and higher-rank metamorphic rock fragments notably increase from uppermost Miocene to Pleistocene deposits, which is ascribed to the onset of rapid exhumation of the Eastern Himalayan syntaxis since ∼ 5 Ma. The same trends are documented in Nicobar Fan turbidites, confirming that they belong to the same sedimentary system. Both Bengal and Nicobar fans record a pulse in mass accumulation rate at Tortonian times, when supply of sedimentary and very-low-grade metasedimentary detritus reflected accelerated exhumation of the Lesser Himalaya. In contrast to foreland-basin sediments, where ferromagnesian minerals have been completely dissolved in strata as young as Pliocene–Pleistocene, in both Bengal–Nicobar and Indus fans amphibole invariably represents about half of the moderately rich to rich transparent-heavy-mineral suite, demonstrating that amphibolite-facies Greater Himalaya metamorphic rocks were widely exposed in the Himalayan range well before the late Miocene and possibly since the late Oligocene, as indicated by a few sillimanite and kyanite grains in Bengal Fan sediments as old as 23 Ma and 28 Ma, respectively. Diagenetic dissolution strongly affected olivine and pyroxene in strata older than the middle and early Pleistocene, respectively, whereas amphibole decreases markedly through progressively older Miocene strata. Ferromagnesian minerals and sillimanite are almost completely dissolved in lower Miocene strata, where durable zircon, tourmaline, rutile, and apatite make up half of the strongly depleted heavy-mineral assemblage. Quaternary turbidites from the six studied cores have virtually the same compositional signatures, testifying to efficient homogenization by turbidite transport and reworking across the fan. Turbidites in western cores closer to peninsular India (U1444A and U1454B) are not different from those in eastern cores, indicating very minor supply from the subcontinent. Forward-mixing calculations based on integrated petrographic and heavy-mineral data indicate that sand supply from the Brahmaputra River to Quaternary turbidites was four times larger than supply from the Ganga River, indicating up to six times higher sediment yields and erosion rates in the Brahmaputra than in the Ganga catchment, largely reflecting superfast erosion of the Eastern Himalayan syntaxis.

Sand, wind, paleosols, war: Late Quaternary aeolian dynamics in the Selima Sand Sheet Region, Darb el Arba'in Desert, Southern Egypt

First scientifically documented by the British explorer and soldier Ralph Alger Bagnold, the Selima Sand Sheet is an extensive low-relief area located within the modern hyperarid core of the Eastern Sahara. Field survey and trenching reveal a surface mantle of near ‘pinstripe” laminated aeolian sands that comprise active chevron (or zibar) bedforms, which are apparent on satellite datasets. These active sands cover Quaternary paleosols with morphostratigraphic characteristics that reflect differing degrees of soil development over time as a function of in situ weathering of quartz parent materials, addition of silts and clays via illuviation and eluviation processes, the precipitation of carbonates, rubification, and bioturbation by plants and insects. A relative chronostratigraphy is inferred from the associated archaeological (Neolithic) and historical materials (Late Historic to World War II), and absolute ages for these deposits are provided by optical dates using single aliquot regeneration techniques (SAR). Constraining the timing of aeolian sedimentation provides a basis for reconstructing paleoenvironmental changes and pedogenesis over Late Quaternary timescales in this region of northeast Africa. Accretion of the sand sheet was episodic and occurred during time periods of enhanced aeolian activity at ∼20–14 and ∼5–3 ka years ago. Late Pleistocene deposition of the sand sheet was out-of-phase with the widely recognized period of rainwater-fed “pluvial” playa lake formation and wadi river drainage alluviation documented in the Sahara, which resulted from enhanced monsoonal rains associated with the orbitally-forced precessional insolation maximum in the Northern Hemisphere. Enhanced bioturbation processes associated with wet phases during the Holocene have completely obliterated most primary sedimentary structures in the Pleistocene-aged sand sheet, resulting in the development of a cohesive, coarse sand and granule-dominated deposit exhibiting incipient prismatic soil structural development. The younger sand sheets dating to the Late Holocene (∼4–3 ka years ago) preserve primary sedimentary structures (e.g. planar laminations), and increasing amounts of cohesion and structure with age. Reconstructing the maximum estimated accumulation rates, and assuming approximately uniform rates of sedimentation across the Selima Sand Sheet area, sediment storage within the sand sheet may be on the order of ∼7 km3/1000 years during the time period that has elapsed since the mid-Holocene onset of arid conditions.

Presence of boulders associated with an extreme wave event in the western Mediterranean (Cape Cope, Murcia, Spain): possible evidence of a tsunami

The region of Murcia, in the southeast of the Iberian Peninsula, experiences moderate tectonic activity, with earthquakes of up to 6.2–6.9 Mw recorded. Even with seismic activity of this scale there is no geological or instrumental record of tsunamis affecting the area. The presence at Cape Cope, Murcia of a ridge of metre-sized imbricated boulders (comprised of Upper Pleistocene sediments) reaching a height of up to 4 m above sea level, indicates that there has been an extreme wave event in the area during the Holocene. Through studying the wave conditions generated during large storms in this area, the boulder ridges appear to have been caused by extreme waves associated with a seismic event, as a tsunami.

Sedimentology and palaeoenvironmental reconstruction of the late Pleistocene deposits along the Bizerte Coast, N-E Tunisia

The N–E Tunisian coast (Bizerte region) shows several Quaternary sedimentary archives of middle to late Pleistocene age. Sedimentological analyses carried out (grain size, morphoscopy, exoscopy, petrography, mineralogy, and fossil content) on 12 sections reveal a succession that begins with infratidal deposits attributed to the last Interglacial period, followed by intertidal, continental (palaeosol) and/or aeolian deposits (aeolianites). The arrangement of these deposits, their lithological characteristics and their faunal contents are the basis for a palaeoenvironment reconstruction and estimation of palaeoclimatic conditions. A warmer climate and a high sea level characterize the beginning of this interval, followed by a sea level fall accompanied by an alternation of humid and arid climate. This alternation is reflected by intercalations of the palaeosol levels between the aeolian deposits.

<i>RHINOLOPHUS MEHELYI SCYTHOTAURICUS</i> SUBSP. NOV. (RHINOLOPHIDAE, CHIROPTERA) FROM THE LOWER PLEISTOCENE OF THE TAURIDA CAVE IN CRIMEA

A new extinct subspecies of the Mehely’s horseshoe bat, Rhinolophus mehelyi scythotauricus subsp. nov., is described on the base of an incomplete skull from the Lower Pleistocene deposits of the Taurida cave in the central Crimea. It is the largest member of the R. euryale group. In terms of the evolutionary level, it is intermediate between Plio-Pleistocene R. mehelyi birzebbugensis Storch, 1974 and recent members of the species, but its large size and relatively narrow upper molars may indicate belonging to a separate phylogenetic lineage within R. mehelyi Matschie, 1901. R. mehelyi scythotauricus subsp. nov. is the first fossil record of the species in the Crimea; it is also one of the northernmost finds of R. mehelyi.

The history of olive cultivation in the southern Levant.

The olive tree (Olea europaea L. subsp. europaea var. europaea) is one of the most important crops across the Mediterranean, particularly the southern Levant. Its regional economic importance dates at least to the Early Bronze Age (~3600 BCE) and its cultivation contributed significantly to the culture and heritage of ancient civilizations in the region. In the southern Levant, pollen, pits and wood remains of wild olives (O. europaea subsp. europaea var. sylvestris) has been found in Middle Pleistocene sediments dating to approximately 780 kya, and are present in numerous palynological sequences throughout the Pleistocene and into the Holocene. Archeological evidence indicates the olive oil production from at least the Pottery Neolithic to Chalcolithic transition (~7600-7000 BP), and clear evidence for cultivation by, 7000 BP. It is hypothesized that olive cultivation began through the selection of local genotypes of the wild var. sylvestris. Local populations of naturally growing trees today have thus been considered wild relatives of the olive. However, millennia of cultivation raises questions about whether genuine populations of var. sylvestris remain in the region. Ancient olive landraces might thus represent an ancient genetic stock closer to the ancestor gene pool. This review summarizes the evidence supporting the theory that olives were first cultivated in the southern Levant and reviews our genetic work characterizing local ancient cultivars. The significance and importance of old cultivars and wild populations are discussed, given the immediate need to adapt agricultural practices and crops to environmental degradation and global climate change.

Glacial expansion of cold-tolerant species in low latitudes: megafossil evidence and species distribution modelling.

Fossil wood of Chinese white pine (Pinus armandii Franch.) from the Late Pleistocene deposits of Maoming Basin of South China provides the first megafossil evidence for glacial expansion of the range of a cold-tolerant species in low latitudes.

The Missing Late Pleistocene Ostrich Femur from Zhoukoudian (China): New Information Provided by a Rediscovered Old Cast

A complete ostrich femur from the Late Pleistocene deposits of the Upper Cave at Zhoukoudian (China) was referred by Shaw to Struthio anderssoni in the 1930s, but its present whereabouts are unknown. A good quality plaster cast of the missing specimen has been found in the collections of the Natural History Museum (London). This cast provides interesting information about the morphology of this large ostrich femur, which had previously been only summarily described and not illustrated. Although smaller than the femora of the Early Pleistocene giant ostrich Pachystruthio, the robust femur from Zhoukoudian shows morphological similarities with them, and it is suggested that ‘Struthio’ anderssoni should be placed in the genus Pachystruthio. The importance of old palaeontological casts is emphasized, as well as the need to preserve and curate them properly.

Early Pleistocene charophyte flora from Dursunlu (Ilgın Basin, Turkey): palaeoecological implications

Here, a charophyte assemblage from lower Pleistocene deposits at the coal mine locality of Dursunlu (Ilgın Basin, Turkey) is described and illustrated for the first time. The assemblage is composed of 11 species recovered from 50 samples taken from an 18 m-thick sedimentary sequence. The base of the sequence is dominated by lignites and organic-rich claystones/siltstones with root marks attributed to palustrine facies. The charophyte assemblage in this palustrine interval is dominated by Chara vulgaris and C. globularis. The upper part of the section is constituted by light grey-yellowish marls, siltstones and a limestone bed related to shallow lacustrine deposits. Two charophyte species dominate this lacustrine interval, Chara hispida and Nitellopsis obtusa, which occurred in intervals in association with Chara pappii, Chara molassica var. notata, Chara sp.1, Chara sp.2, Sphaerochara prolifera, Sphaerochara intricata and Lychnothamnus barbatus var. antiquus. The palaeoenvironmental characteristics and evolution of the Ilgın palaeolake during the Early Pleistocene (Günz glaciation) are inferred from a facies analysis and the ecological requirements of the charophyte assemblages. The results suggest that during this glacial period, the Ilgın Basin was occupied by a very shallow eutrophic lake with a dense palustrine vegetation belt, which evolved to a shallow (2–15 m deep), stable, oligotrophic, alkaline and oligohaline lake. The increase in water availability in the palaeolake can be related to climatic oscillation during the Günz glaciation. Finally, the lake depocentre migrated towards the NW due to tectonism, and these deposits were later subjected to intense pedogenic alteration.

Northern Urals (Russia) quaternary deposits and biostratigraphical record caves and grottoes

Investigations of the unconsolidated Upper Pleistocene – Holocene cave deposits of the Northern Urals resulted in detailed biostratigraphical and palaeoenvironmental data. The article summarizes data from important stratigraphical levels exposed in 19 cave localities, most part of which represent several layers dated to different periods. These data cover the period from the beginning of the Upper Pleistocene (MIS 5-4) to the end of the Upper Holocene. At the beginning of Marine Isotope Stage 3 (MIS 3), open woodlands were distributed, which at the end of MIS 3 were replaced by Forest–steppe landscapes. At the beginning of MIS 2 (LGM), Periglacial steppe landscape was distributed. At the end of MIS 2 and at the beginning of the Holocene (MIS 1), semi-open landscapes were common. At the beginning of the Middle Holocene, they were replaced by taiga landscapes. Fish were present in the fauna of the Northern Urals in the Upper Pleistocene and Holocene. Amphibians in the Upper Pleistocene as part of the fauna of the region appear only at its beginning (MIS 5-4) and end (Bølling – Allerød period). Since the beginning of the Holocene (MIS 1), they have been constantly present in the fauna of the Northern Urals. Reptiles appear in the fauna of the region only in the Middle Holocene. During the Upper Pleistocene, the avifauna and fauna of small mammals were dominated by species of open landscapes, and the fauna of large mammals was dominated by species of open and semi-open landscapes. At the beginning of the Holocene, the avifauna and theriofauna increased the number of species associated with tree and shrub vegetation and near-aquatic species. Since the beginning of the Middle Holocene, the avifauna and theriofauna have been dominated by species of taiga landscapes. Palynological data and data on the fauna of small and large mammals allow us to separate the deposits of the Upper Pleistocene and Holocene. These data also allow us to separate the deposits of the beginning (MIS 5-4), middle (MIS 3), end (MIS 2)) of the Upper Pleistocene, Lower, Middle and Upper Holocene (MIS 1).

Cervidae and Tayassuidae of the Late Pleistocene from the Cuvieri Cave, Eastern Brazil

The Pleistocene of the eastern Brazilian territory is characterized by a great diversity of extinct and living mammals. The Cuvieri Cave, part of the Lagoa Santa karst complex, presents an abundant amount of osteological material dated from the Pleistocene, resulting in an important record of changes in faunal composition and environmental settings. In this cave, Cervidae are represented by two extant species: Mazama americana and Mazama cf. gouazoubira, while the Tayassuidae family is the most abundant of Pleistocene macrovertebrates and is represented by two species. One of the species was identified as Dicotyles tajacu, showing anatomical features larger than recent specimens from the same region, but similar in size to Amazonian specimens. The most common observed species could not be identified and is much larger than the living Tayassu pecari, the largest Tayassuidae in the region and to the Pleistocene deposits of Cuvieri Cave. The Cervidae species are the same observed in the Holocene, but the differences of the Tayassuidae in relation to the living specimens suggest that paleoenvironmental changes occurred after the deposition.

Microbial utilization of recently fixed, plant-derived organic carbon in shallow Holocene and Pleistocene aquifers in Bangladesh

The presence of dissolved arsenic in shallow aquifers of Bangladesh is widely accepted to require microbial dissimilatory iron-reduction in anoxic aquifers utilizing organic carbon as an electron donor. However, the various potential sources of this carbon, and whether organic carbon sources vary with sediment age (i.e. < 12 kyr-old Holocene vs older Pleistocene sediments) are still poorly understood. To shed light on these questions, natural abundance radiocarbon signatures of in situ microbial phospholipids fatty acids (PLFA), concentrations of sterol biomarkers, and aqueous [Cl-] and [Br-] were compared in two Bangladesh aquifers; a shallow (11–15 m) aquifer low in dissolved arsenic containing oxidized (orange) Pleistocene sands, Dopar Tek (DT), and a shallow (6–21 m) aquifer high in dissolved arsenic containing reduced (grey) Holocene sands, Desert Island (DI). Radiocarbon signatures of PLFA (Δ14CPLFA = −30 to −63 ‰ and +9 to +25 ‰, respectively) indicate microbial utilization of carbon fixed from the atmosphere within the last several decades, the drawdown of which into the shallow portions of both the Pleistocene Dopar Tek and Holocene Desert Island aquifers was likely enhanced by regional pumping activities. Similar results were previously obtained for two other Holocene aquifers in the same region, but to our knowledge this is the first time modern PLFA has been extracted from Pleistocene sediments. At both sites, high proportions of phytosterols, low sewage contamination indices (SCI < 0.7), and generally low Cl/Br ratios (averaging 434 and 544 at Desert Island and Dopar Tek respectively), are consistent with predominantly plant-derived organic carbon inputs. This contrasts with sewage-derived input inferred from higher sewage contamination index values (>0.7) previously observed at the two other shallow Holocene aquifers in the same region. Overall, our observations show that microbial communities within shallow aquifers, including those of Pleistocene age, utilize very recently fixed organic carbon associated with both plant and/or sewage origin. The microbial utilization of organic carbon fixed within the past several decades, likely derived from plants, in the anaerobic Pleistocene, has not, as of yet, led to iron reduction that would be sufficient to increase arsenic concentrations in groundwater. However, the observed microbial utilization of recently fixed carbon within all Bangladesh aquifers studied to date, indicates that pumping enhanced drawdown represents a potential risk to any systems where it might occur.

Temporally varied coastal uplift rates north of the Littoral Fault Zone since the late Quaternary in the northern South China Sea: Insights from the wave-cut platform and cosmogenic exposure dating

While understanding the long-term slip rate of active normal faults is essential for the comprehensive assessment of seismic activity, it is difficult due to the absence of age control in the erosional bedrock region. The preserved sequence of wave-cut platforms in granite allows exploration of the long-term slip rate in the footwall of some normal faults. We investigated wave-cut platforms in the southern Pearl River Delta (PRD), a coastal delta transected by the seismically active Littoral Fault Zone (LFZ) in the northern South China Sea, to derive slip rates and their impacts on the seismic hazard potential. We mapped a flight of four wave-cut platforms (T1–T4), dated the T2 and T4 platforms by 10Be cosmogenic nuclide dating, and used the absolute age to correlate the un-dated platform to global sea-level highstands. Our results allocate the ages of 128 ka, 197 ka, and 239 ka to the upper three wave-cut platforms and yield temporally various uplift rates ranging from 0.30 to 0.38 mm/a during 239–128 ka to 0.09 mm/a since 128 ka. A decrease in the uplift rate, which coincided with a decreased subsidence rate within the PRD in previous work, implied a weakened differential uplift onshore of the LFZ system. Our findings infer that the transgression event occurred as early as marine isotope stage (MIS) 7 in the PRD, consistent with the view that Pleistocene sedimentation began in MIS 5 or earlier in the PRD.