Holocene Age Research Articles

Enhancing biodiversity: historical ecology and biogeography of the Santa Catalina Island ground squirrel, Otospermophilus beecheyi nesioticus.

People have influenced Earth's biodiversity for millennia, including numerous introductions of domestic and wild species to islands. Here, we explore the origins and ecology of the Santa Catalina Island ground squirrel (SCIGS; Otospermophilus beecheyi nesioticus), one of only five endemic terrestrial mammals found on California's Santa Catalina Island. We synthesized all records of archaeological/palaeontological SCIGS, conducted radiocarbon dating and stable isotope analysis of the potentially earliest SCIGS remains and performed genetic analysis of modern SCIGS. Squirrels were not identified in island palaeontological deposits, but at least 12 island archaeological sites contain SCIGS bones, including some that are butchered or burned. All directly dated SCIGS bones are Late Holocene in age and younger than approximately 1290 cal BP. The first mitochondrial genome for modern Otospermophilus beecheyi and 15 modern SCIGS mitogenomes document at least one introduction of squirrels. Stable isotope data indicate variable SCIGS diets and potential subsidies from marine environments to terrestrial plants consumed by some individuals. We cannot rule out a natural overwater dispersal, but the earliest SCIGS remains post-date the earliest evidence for people by several millennia and, along with other lines of evidence, support a human-assisted translocation of squirrels during the Late Holocene. These data illustrate the important role of Indigenous people in shaping and enhancing island biodiversity and ecology around the world.

Tectonic ledges at the Ladoga Lake bottom

For the past few years, the Institute of Limnology of the Russian Academy of Sciences has been conducting geological and geomorphological studies of the bottom of Lake Ladoga. Starting from 2018, underwater photo and video cameras developed at the Institute began to be used in these studies. The use of this new research tool led to the discovery of a number of new facts about the structure of the bottom of Lake Ladoga. In particular, at the bottom of the northern part of Lake Ladoga, three subvertical ledges were found, composed of bedrock, up to 70–100 meters high. According to a number of features, such as the bedrock composition of rocks, morphology and spatial correspondence to known fault zones, these ledges can be recognized as morphological expressions of tectonic objects – faults of presumably fault type. The absence of visible traces of glacial processing on the bedrock blocks suggests the Holocene age of the formation of these ledges and, accordingly, the existence of modern active tectonic movements in the area of Lake Ladoga.

Olivine Time-Capsules Constrain the Pre-Eruptive History of Holocene Basalts, Mount Meager Volcanic Complex, British Columbia, Canada

Abstract The Canadian segment of the Cascade Volcanic Arc (i.e. the Garibaldi Volcanic Belt) comprises more than 100 eruptive centres, spanning the entire Quaternary period (Pleistocene to Holocene in age), and with deposits ranging in composition from alkaline basalt to rhyolite. At least one of the volcanoes is currently active; Mount Meager / Q̓welq̓welústen erupted explosively 2360 years BP and has ongoing fumarolic activity. Long-term forecasting of eruption frequency and style depends on reconstruction of the history and timescales of magmatic processes preceding previous volcanic eruptions. Utilising diffusion chronometry, we investigate the Mount Meager Volcanic Complex focusing on Holocene olivine-phyric basalts (Lillooet Glacier basalts) exposed by the retreat of the Lillooet Glacier. We identify two distinct olivine populations in samples of quenched, glassy basalt lavas that record different magmatic processes and histories. Glomerocrysts of Fo83 olivine phenocrysts, entrained and transported by a hot mafic input, form Population 1. These exhibit resorption and normally zoned outermost rim compositions of Fo76–78; a third of them also show interior reverse compositional zoning. A second population of skeletal microphenocrysts have the same composition as the phenocryst rims (i.e. Fo76–78) and are in equilibrium with the adjacent matrix glass. We estimate the pre-eruptive temperature-fO2 conditions in a shallow reservoir (100 MPa; ~3 km) for a melt with H2O content of 0.5 to 1 wt % as ~1097°C to 1106°C (± 30°C), and NNO + 0.5 (±1.1), respectively. Using these input parameters, we report Fe-Mg diffusion chronometry results for 234 normally zoned profiles from 81 olivine phenocrysts. Diffusion modelling of compositional profiles in oriented crystals indicates pre-eruptive magmatic residence times of 1 to 3 months. These remarkably short residence times in shallow reservoirs prior to eruption suggest very short periods of unrest may precede future eruptions.

Abundance of submarine volcanism in arcs

Explosive submarine arc volcanoes can cause tsunamis, affect climate, and pose hazards to airplanes and ships. Although 70 % of the Earth is submarine, only 15 % of Holocene arc volcanoes in the Smithsonian Global Volcanism database are submarine. Merging locations of active submarine hydrothermal vents in arcs and the above database, we found 71 unlisted submarine arc volcanoes. Using Baker [2017, doi: 10.1016/j.oregeorev.2017.02.006], only 44 % of hydrothermal vents in arcs are known. Only 77 of the vent fields are on volcanoes in the Smithsonian database. Assuming that unknown submarine arc volcanoes are present in the same proportions as unknown vents, there are ~160 as-yet undiscovered Holocene age submarine arc volcanoes. Using geophysical data, we located 291 unsurveyed seamounts <30 km from arc axes, the distance within which active vents occur. We estimate 119±16 have active vents. Because more unknown seamounts exist, this means that >32 % of Holocene arc volcanoes are submarine.

A pragmatic approach of hydrochemical and irrigation indices of groundwater quality of district Ballia, U.P. India

ABSTRACT In the groundwater aquifer media, enormous amounts of ions can be found naturally in rocks from the Pleistocene and Holocene ages. There are several reports of metals and ionic contamination in the different blocks of the Ballia district. This article focuses on a thorough investigation of the hydrogeochemical properties and the cause of ionic contamination in the Ballia district's groundwater system. This article discusses the interactions between the numerous cations and anions that are hydro-geologically present as well as several physico-chemical factors. The relationship analysis was conducted utilizing irrigation indices and a Stufzand classification, which was further supported by a Durov and Stiff plot. The Durov plot shows the mineralization of the aquifer by sand and evaporates of geological formation. The Gibbs plot shows that the rock–water interaction, weathering of silicates, evaporates dissolution, carbonate dissolution, and anthropogenic activities. The Stiff plot shows the highest concentration of Mg-rich minerals and Cl due to the weathering of calcite, amphiboles, and anthropogenic activities also proven by the Irrigation indices and Stufzand classification. The high water quality index (WQI) value was discovered to be mostly due to greater EC, total dissolved solids, hardness, nitrate, sulfate, chloride, and magnesium levels in groundwater.

A combined tectono-climatic control on Holocene sedimentation in Ladakh Himalaya, India: Clues from Anisotropy of Magnetic Susceptibility (AMS) of lake sediments

Anisotropy of Magnetic Susceptibility (AMS) data from a ∼27.8 m thick soft sedimentary mud sequence (∼10.5–3.25 k yrs) from the Spituk Palaeolake Sequence (SPSS) of Holocene age, located in the northern bank of the Indus River in the Leh-Ladakh Himalaya, show effects of tectonic versus climate dynamics responsible for the Himalayan sedimentation. The sedimentary sequence, consisting of alternating of aeolian sand and glacio-fluvial mud flow deposits, has been subdivided into an older Last Glacier Phase I (LGP 1) and a younger Last Glacier Phase II (LGP 2), where the termination of each phase is marked by the occurrence of gravel beds of thickness ≤1 m, which were deposited due to glacial melting. The present AMS data along with previously published information on sedimentology confirm that the mudflow deposits of the LGP 1 and LGP 2 phases were deposited in a lacustrine environment under glacio-fluvial conditions. However, a weak fluvial flow towards NW and NE could have existed for the LGP 1 and LGP 2, respectively. The glacial beds terminating LGP 1 and LGP 2 appear to have formed by climatic warming and tectonic activity, respectively. Hence, the Holocene Himalayan sedimentation was influenced by both climatic and tectonic activities. However, the thickness of the gravel bed (∼0.8 m) terminating LGP 2 occupies only ∼ 2.8 vol % of the total studied thickness ∼28 m, of the SPSS in the present study, which indicated a lesser control of tectonism in the growth of the Himalaya in and around the study area.

Palaeoenvironmental reconstruction of Holocene calcareous tufas distributed over a manganese deposit in Mexico

The Holocene calcareous tufa deposits are located in the north-central sector of the state of Hidalgo, Mexico. These deposits outcrop on the Upper Jurassic Chipoco Formation in the Molango Manganese District. Calcareous tufa deposits correspond to carbonate formations of inactive tufas disconnected from the current hydrological network. To better understand the textural, geochemical, and biological characteristics and environmental conditions during their formation, a detailed study involving field analysis, X-ray diffraction analysis, X-ray fluorescence analysis, and morphometric analysis with light microscopy, and scanning electron microscopy was carried out. Similarly, 14C analysis was undertaken to determine the age of the deposit. On this basis, two biofacies were defined, one with stem structures and the other with Phyto clasts, bryophytes (Plagiomnium cuspidatum), and copepods, limited both at the base and the top by lenticular-shaped erosive surfaces and sigmoidal clinoforms. These bio facies formed in lacustrine and paludal environments, and barrier waterfalls. From a geomorphological point of view, the accumulations of these calcareous tufas originated on slopes and/or at the foot of karstic springs, where the accumulation of material originated from the height of the spring with respect to the bottom of the valley, giving rise to a set of stepped tuffaceous plains with a wedge-shaped profile, colonized by important masses of bryophyte mounds, copepods, and vascular plants. This suggests a swampy environment where sedimentation took place in shallow water accumulations, where there is clear evidence of exposure and pedogenetic modification, indicating wet and dry episodes that translate into seasonal fluctuations in the water table. Six mineral phases were observed including silicates, carbonates and arsenates. The 14C analysis indicates that the plant found in the charcoal sample within the calcareous tufa deposit is of Holocene age.

PALAEOECOLOGICAL SITUATION IN PRE-DELTA AREA OF THE NORTH CASPIAN SEA DURING THE HOLOCENE

Palaeoecoligical reconstructions of predelta area of the North Caspian Sea were based on the multidisciplinary study of the core from the Rybachya borehole containing the Holocene deposits. Geochemical, grain size, mollusk fauna, diatom and ostracod analyses were performed, and the radiocarbon dating was carried out. The structure of deposits reflects palaeogeographic events of different scales including the inception of a palaeoincision in the Lower Khvalynian deposits, accompanied by erosion of the Upper Khvalynian deposits; its development during the Mangyshlak regression and gradual filling during the multistage Holocene Neocaspian transgression. The Holocene age of the deposits filling the palaeodepression is confirmed by radiocarbon dates - 8070 ± 110 and 7020 ± 140 cal. BP. The paleontological data indicate the interchange of tranquil and dynamic water regimes and the quasicyclical change in the conditions of the water basin, from brackish to freshwater and to marine during the stage of sedimentation, corresponding to the presentday conditions on the North Caspian shelf.

Loess formation and chronology at the Palaeolithic key site Rheindahlen, Lower Rhine Embayment, Germany

Abstract. The loess–palaeosol sequence and intercalated Palaeolithic find layers at the former brickyard of Rheindahlen are matters of ongoing scientific dispute. The age of different palaeosols and loess layers, hence their correlation with the global climate cycles, and the timing of repeated Neanderthal occupations have been hotly debated. These disagreements should be solved because the exceptional sedimentary and Palaeolithic sequences at Rheindahlen provide a unique opportunity to study diachronic changes in Neanderthal behaviour within the context of past climate change. We thus revisited one of the key loess sections of the Rheindahlen site to improve our understanding of loess formation processes and provide a more reliable chronostratigraphic framework for the sequence. High-resolution grain size analyses and micromorphology show that the Erkelenz Soil and the Rheindahlen Soil are characterized by more strongly developed Bt horizons than the modern soil. While these soils represent interglacial phases, the lowermost palaeosol likely formed during an interstadial and has been overprinted by weak clay illuviation during the formation of the Rheindahlen Soil. Sedimentary features of prolonged frost characterize loess and palaeosols below the modern soil and give indirect evidence for a Holocene age of the uppermost part of the sequence. Our luminescence dating approach corroborates this correlation and adds several Last Glacial deposition ages for the upper metres of the sequence. Previous correlation of this part of the sedimentary sequence with the penultimate glacial is thus rejected, whereas placing the Middle Palaeolithic inventories A3, B1, and B2 into the Last Glacial is confirmed. Luminescence measurements for the parental loess of the Erkelenz Soil and for loess layers below did not provide reliable ages probably related to signal saturation. The age of this part of the sequence thus remains open, hence the timing of human occupation testified by Palaeolithic inventories B3, B4/5, C1, and D1. The new findings provide an improved base for stratigraphic correlation of the Rheindahlen loess sequence and for investigating diachronic change in Neanderthal behaviour against the background of past climate change.

Каменный век Камчатки: переход от палеолита к неолиту

The article describes general and peculiar features of transition from the Palaeolithic to the Neolithic on the Kamchatka peninsula. The findings are obtained through studying multi-layered camps of Ushki and artefact of Anavgay II and Razdelny II sites. The objective of the article is to systematize archaeological and stratigraphic materials, both the new ones and the ones already existing in the scholarly discourse. The objective implies description of the functioning of the human culture in the Stone Age Kamchatka with regards to the dynamics of natural complexes. It is established that the peculiarity of the transition from the Palaeolithic to the Neolithic on the Kamchatka peninsula is three consequent and differently looking tangible culture complexes: the Final Palaeolithic (~13.3–12.5 thousand years B.P. calibrated; 12.0–10.1 thousand years B.P. calibrated) and the Mesolithic (~9.9–8.6 thousand years B.P. calibrated). The peculiarities of the first complex imply bifacial arrowheads and darts with shafts, stone embellishments (pendants, beads), artificial organic colourings; distinctive feature of the second complex is evidence of using the micro plate technology (Yūbetsu technique); the third complex is represented with the micro lithic technique of tool production and plate- and flake-based tool sets. The population of all complexes is characterized with appropriating economy based on preying on different animal and bird species, fishing and gathering. Two Late Pleistocene cultural complexes are typical for the Final Palaeolithic Eurasia and America in terms of their settlement arrangements, stone industry, economy and symbolic behaviour. The third period demonstrates the Early Holocene age and certain materials, which makes it associated with the Mesolithic. The Mesolithic complexes’ stone industry shows predominant items based on prismatic plates. There is no ceramics found. There are common features with the Mesolithic cultures of Eurasia. The dynamic and migration of the Kamchatka population in the researched period was linked to the volcanic activity, endogenous landscape formation and associated consequences.

Characteristics of the Kematu epithermal gold deposit at Tboli, Mindanao, Philippines

AbstractThe Kematu Au‐Ag epithermal deposit at Tboli area, Province of South Cotabato, Mindanao, Philippines, contains an inferred mineral resource of 3.8 million tonnes, at 8.7 g/t Au and 27 g/t Ag in 2012. The deposit is spatially and genetically linked to the volcanism related to the Parker Volcanic Complex of Pliocene to Holocene age. Local extension of the northwest‐trending splays of the faults in the Tboli area are associated with epithermal mineralization, including the Kematu Au‐Ag deposit. The study aimed to provide a detailed description of the characteristics and physicochemical processes involved in the formation of the Kematu Au‐Ag deposit on the basis of field occurrence, mineralogy, ore composition, mineral chemistry, and sulfur isotope data. The deposit is characterized by Au‐Ag bearing quartz‐adularia‐clay‐sulfide veins hosted in argillic‐altered andesite porphyry and coarse tuff of the Parker Volcanic Complex. The mineralization in the Kematu deposit is in the form of veins as well as open space fill and dissemination. Based on the observation of the ore bodies and petrographic analysis, three paragenetic stages with different vein characteristics have been identified. Stage 1 is dominantly quartz, adularia, and clay mineral veins, with electrum, sphalerite, pyrite, chalcopyrite, tetrahedrite‐tennantite, and galena. Stage 2 is coarse‐grained sulfide‐quartz‐adularia veins and in‐fill of vugs, consisting of sphalerite, pyrite, chalcopyrite, galena, tetrahedrite‐tennantite, and electrum. Stage 3 is massive calcite veins, with minor amounts of electrum, sphalerite, pyrite, chalcopyrite, and galena. The alteration mineral assemblage of the host rocks is chlorite‐illite‐adularia, indicative of neutral pH conditions. The FeS content of the Fe‐poor sphalerite in the stage 2 ranges from 0.03 to 1.07 mol%. Sulfur isotope compositions (δ34SCDT) of sulfides in all the stages range from 0.1‰ to 1.9‰ for pyrite, and −5.3‰ to 0.5‰ for galena, sphalerite, and chalcopyrite, where those in the stage 2 tend to have relatively lower values compared to those in the stages 1 and 3. The relatively narrow and close to zero δ34SCDT values suggest that the sulfur was mainly derived from a magma. The mineral assemblages of the stages 1, 2, and 3, and the sulfur fugacity (log fS2 = −12.5 to −8.8) and temperature (200–280°C) of ore formation based on the FeS mol%, electrum composition (at.%), and alteration mineral assemblage suggest that the Kematu deposit is of intermediate sulfidation type.

Primary source of titanomagnetite ores at the Orokolo Bay placer deposit: Implications for petrogenesis

AbstractCoastal and river sand sequences of Holocene age at Orokolo Bay in Papua New Guinea are host to secondary titanomagnetite ore deposits. The resource developer (Mayur Resources) declares a measured orebody of 139 million tons at grades of 11.35% Fe, 1.94% Ti, and 712 ppm Zr. Orokolo Bay is located near the boundary between the Papuan Thrust and Fold Belt and the Aure Fold Belt. This region is characterized by sedimentary rocks of the Papuan Basin, which are intruded and overlain by a diverse array of magmatic intrusive and volcanic rocks, ranging from mafic alkaline to felsic calc‐alkaline types related to arc–continent collisions in the Cenozoic. The Vailala and Purari rivers located to the east and west of Orokolo Bay, respectively, are the main sediment pathways. Earlier provenance studies have suggested that the deposited sediments mainly come from the erosion of volcanic rocks found within the catchments of these two rivers. However, these studies did not specifically identify the primary source of the Fe‐Ti ores within this region. Here, we report on a potential primary source of the Fe‐Ti ores by examining the occurrence and chemical compositions for detrital titanomagnetites, and associated pyroxene and amphibole minerals. The purpose of this was to discern specific attributes of the primary source for its identification. Lithic sediments comprised of magnesio‐hornblende (Mhbl), tschermakaite (Tsr) and magnesio‐hastingsite (Mhst) amphiboles, clinopyroxene (Cpx), and Fe‐Ti oxide minerals dominate the heavy sands. Feldspar is more abundant than quartz, and Cr‐spinel is rare. Two primary titanomagnetite types were categorized based on their homogeneous grain textures and TiO2 content, Tmt1 (average 28 wt% TiO2) and Tmt2 (average 7 wt% TiO2). Pleonaste exsolutions and zircon inclusions distinguish Tmt1 from Tmt2, while apatite and quenched glass inclusions occur in both. A portion of both primary titanomagnetites exhibits hydrothermal overprinting, this subset was categorized as Tmt3 (average 12.5 wt% TiO2). Fe‐Ti oxides are associated with Cpx and amphiboles as inclusions, and as pseudomorphs in opacitic amphiboles. Tmt1 coexists predominantly with Mhst‐Tsr but also appears less frequently with Mhbl and Cpx. Tmt2 occurs almost exclusively with Mhbl and Cpx. Titanomagnetite chemistry is low in Cr, Mg, and V content suggesting crystallization from evolved melts. Tmt3 is shows enriched Si, Ca, Al, and Mg concentrations that are characteristic of late‐stage fluids derived from calcareous rocks. Amphibole and Cpx chemistry indicate they were derived from a subalkaline source magma of arc affinity. Fe‐Ti thermobarometry reveals Tmt1 (990 to 967°C, −0.51 to −0.18 ΔNNO) formed at higher temperatures and in less oxidized conditions than Tmt2 (834 to 689°C, 0.33 to 3.2 ΔNNO). Amphibole thermobarometry reveals Mhst‐Tsr and Mhbl formed under similar conditions as Tmt1 and Tmt2, respectively. The lack of Cr‐spinel, olivine, and the abundant occurrence of zircon and Mhbl indicate an evolved subalkaline source characterized by felsic rocks related to arc magmatism. The only volcanic source which aligns with these characteristics is Mount Yelia within the Vailala River catchment. Compositional variation between Tmt1 and Tmt2 titanomagnetites and associated silicate minerals is attributed to heterogeneous temperature and ƒO2 conditions within the melt during crystallization. The provenance of Ti‐rich titanomagnetite ores from sources related to arc magmatism indicates the potential of other areas associated with arc activity in Papua New Guinea to host secondary deposits rich in Fe‐Ti ores.

The Sustainability of Using DuraCrete as Cement Additive to Estuarine Soft Soil Stabilization

Large areas of estuarine deposits exist on the coastal plains of the southeast Queensland coast with a countered depth of up to 30 m. These deposits are categorized as sediments that originated during the Holocene Age. The sediments have not been consolidated or subjected to considerable pressure since the end of the Ice Age. The structure of these deposits consists of large ratios of porosity, causing high soil compressibility, which lowers the bearing capacity of the soils. Therefore, the soils of the region cannot maintain sufficient support for construction loads, and consequent malfunctions could occur in short-term and long-term periods. The objective of this paper is to investigate the suitability of new soil stabilization additives in the southeast Queensland region and the optimum additive content of cementitious materials and an advanced mixing modifier branded as DuraCrete. A combination of Portland cement and DuraCrete was used as a soil additive. Three DuraCrete-to-cement ratios were used: 2%, 3%, and 4% by weight. Soil collected from the Port of Brisbane region was treated by adding the additives as a percentage of its weight; four percentages were considered: 10%, 20%, 25%, and 30% for each combination of additives. The performance of the treated soils was examined under unconfined compression after 28 days of curing. The results revealed that increases in the unconfined compressive strength were detected as DuraCrete was added to the mixtures. For 30% additives, increases of about 15%, 34%, and 17% were detected when DuraCrete was added as 2%, 3%, and 4%, respectively. The results also revealed that 3% DuraCrete content provided significant stabilization compared to 2% and 4% for 25% and 30% additive-treated soils; such behavior was also observed for the specimens of 25% content of additives. Additionally, DuraCrete can be considered a promising material that can be combined with cement to obtain the desired stabilization of soft soils.

The vegetation of Holocene coastal dunes of the Cape south coast, South Africa.

The vegetation of calcareous coastal dunes of Holocene age along the south coast of South Africa's Cape Floristic Region is poorly described. This vegetation comprises a mosaic of communities associated with two biomes, Fynbos and Subtropical Thicket. Previously, expert knowledge rather than quantitative floristic analysis has been used to identify and delimit vegetation units. In many areas, mapped units conflate vegetation on Holocene sand with that on unconsolidated sediments of late Pleistocene age, despite pronounced species turnover across this edaphic boundary. Despite dominance by Cape lineages and fynbos vegetation, dune vegetation in the eastern part of the region has been included in the Subtropical Thicket Biome rather than the Fynbos Biome. The high levels of local plant endemism associated with this dune vegetation and the small and fragmented configuration of these habitats, makes it an urgent conservation priority especially when placed in the context of rising sea levels, increasing development pressures and numerous other threats. Here we provide a quantitative analysis of 253 plots of the 620 km2 of Holocene dune vegetation of the study area using phytosociological and multivariate methods. We identified six fynbos and two thicket communities based on the occurrences of 500 species. Following a long tradition in Cape vegetation typology, we used the Strandveld (beach vegetation) concept as our first-order vegetation entity and identified six units based on the fynbos floras. These were, from east to west, Southeastern Strandveld, St Francis Strandveld, Goukamma Strandveld, Southwestern Strandveld and Grootbos Strandveld. Each unit was differentiated by a suite of differential species, most being Holocene dune endemics. The two thicket communities-Mesic and Xeric Dune Thicket-showed limited variation across the study area and were subsumed into the Strandveld units. We discussed our findings in terms of vegetation-sediment relationships, emphasizing the need for a greater geographical coverage of sediment ages to facilitate a better understanding of deposition history on vegetation composition. We also discussed the role of soil moisture and fire regime on structuring the relative abundance of fynbos and thicket across the Holocene dune landscape. Finally, we address the conservation implications of our study, arguing that all remaining Holocene dune habitat should be afforded the highest conservation priority in regional land-use planning processes.

Noble gases in groundwater reflect wet-season temperature in an arid, monsoonal, and mountainous environment

Comparing directly measured soil temperatures with noble gas recharge temperatures (NGTs) inferred from noble gas concentrations indicates that the infiltrating soil water equilibrates with soil air near the soil surface during the rainy season. Therefore, NGTs of groundwater recently recharged by the Indian Summer Monsoon (ISM) in the Dhofar Mountains in southern Oman reflect the soil temperatures of the 3-month period and do not represent an annual mean. This finding highlights the need to account for seasonality when interpreting NGT data in regions with pronounced dry and wet seasons.We extend the observations from the southern flank of the Dhofar Mountains to three wells situated on the northern flank of the Dhofar Mountains. Two of these wells yield water of Holocene age that was recharged by the monsoon, their NGT signals are therefore classified as seasonal. The NGT calculated from a third well for recharge conditions during the Last Glacial Maximum (LGM), when the ISM was absent, is approximately 3 °C lower than that of the two Holocene wells. The lower LGM noble gas temperature corresponds well with the lower annual Sea Surface Temperature (SST) in the nearby Arabian Sea.NGTs from published studies from northern Oman are 1–3 °C higher when compared with our data of the same period in the southern Oman. We explain this regional difference of reconstructed temperatures for the LGM and Holocene groundwater with a more continental climatic influence on the infiltration conditions further to the north. The published NGTs from northern Oman show a large temperature difference between the late Holocene and the LGM. In view of our finding of seasonal NGT signals under monsoonal climate, part of this difference may reflect a change in the precipitation regime rather than in air temperature.

A SUMMARY OF RADIOCARBON MEASUREMENTS OF FLUVIAL AND COLLUVIAL DEPOSITS IN CATCHMENTS OF SOUTH-CENTRAL ONTARIO, CANADA

ABSTRACTFluvial and colluvial deposits of Late Holocene age in South-Central Ontario catchments have provided few 14C dates, most by conventional methods registering century-old ages. Other young deposits, dated by conventional and accelerator mass spectrometry radiocarbon (AMS 14C), have yielded bomb-affected post-1950 ages over variable time limits. Attempts to date the base of Ah and lower-in-section soil horizons, in Early to Late Holocene stream terrace deposits, have yielded atomic bomb effects. Comparing bomb contamination in Late Holocene fluvial deposits, using both conventional and AMS methods, identifies a mix of bomb-affected beds juxtaposed with dated beds, the latter yielding ages with narrow standard deviations. Colluvial deposits overlying key glacial sections in the Rouge Catchment, while rare, yield bracketed AMS ages for an Ahbk horizon that refines weathering times relative to previously obtained conventional 14C dates. Bomb-affected sediment appears variably distributed within floodplain soils and in the ground soil of a colluvial section. Mass wasted deposits, with AMS 14C ages spread over the last few centuries, appear related to Little Ice Age (LIA) changes in climate, corroborated by pollen records. Further, these AMS-14C dated beds calibrate weathering of secondary Fe-Al oxihydroxides over the first half a millennium of weathering time.

Sediment core analysis using artificial intelligence

Subsurface stratigraphic modeling is crucial for a variety of environmental, societal, and economic challenges. However, the need for specific sedimentological skills in sediment core analysis may constitute a limitation. Methods based on Machine Learning and Deep Learning can play a central role in automatizing this time-consuming procedure. In this work, using a robust dataset of high-resolution digital images from continuous sediment cores of Holocene age that reflect a wide spectrum of continental to shallow-marine depositional environments, we outline a novel deep-learning-based approach to perform automatic semantic segmentation directly on core images, leveraging the power of convolutional neural networks. To optimize the interpretation process and maximize scientific value, we use six sedimentary facies associations as target classes in lieu of ineffective classification methods based uniquely on lithology. We propose an automated model that can rapidly characterize sediment cores, allowing immediate guidance for stratigraphic correlation and subsurface reconstructions.

Morphotectonics and paleoseismology of the North Darhad fault (SW Baikal Rift, Mongolia)

The North Darhad Fault, a major N-S fault at the SW Baikal Rift, demonstrates weak present-day activity, but several morphotectonic features indicate the occurrence of strong surface-rupturing earthquakes in the past. The seismic potential of the North Darhad Fault has not been accurately assessed, leaving a gap in the assessment of the seismic hazard. In this paper we present remote and field morphotectonic and paleoseismological studies carried out along this fault system. A detailed topographic mapping of the fault scarp in alluvial surface and trenching across the fault revealed two paleoseismic events responsible for the scarp formation. Dating of organic remnants found in the cross-section allow estimating a Holocene age for the paleoearthquakes and bracket the vertical slip rates along the North Darhad Fault between 0.3 ± 0.06 mm/yr (min) and 0.6 ± 0.12 mm/yr (max) over the last ∼ 8.4 ka. The obtained morphotectonic and paleoseismological data suggest that the North Darhad Fault has produced two magnitude Mw7 earthquakes separated by mean recurrence period of ∼ 3.5 ka. We have demonstrated that within the SW Baikal Rift the ∼ M7-7.5 earthquakes likely occur during temporal clusters along the faults separated in space by up to 250 km. The slip rates along the North Darhad Fault allowed us to compute the age of the Darhad Basin at 6.5–3.3 Ma, suggesting a synchronous formation of fault-controlled horst-graben systems throughout the SW Baikal Rift. The opening of the Darhad Basin fits well into the pull-apart model of deformation between the two largest strike-slip fault systems - Bulnay in the south and Mondy-Tunka-Sayan in the north.

HOLOCENE DISTRIBUTION OF THE ASIATIC WILD ASS (<i>EQUUS HEMIONUS</i>, EQUIDAE, PERISSODACTYLA) IN KAZAKHSTAN

The Asiatic wild ass is one of the last wild, free-roaming equid species left in Northern Eurasia. Once widespread across Asia and Eastern Europe, the wild ass is presently listed as a near-threatened species on the IUCN Red List. The conservation of this species is one of important issues of wildlife ecology, while investigating its prehistoric range may provide some perspective into its current distribution and abundance. However, the data available on its past distribution are limited to the last few centuries. We review the available information using both published and unpublished sources to document the sub-fossil sites in Kazakhstan where bones of the species have been reported. Our analysis reveals 70 such sites of Holocene age ranging from Neolithic to modern years. The past range in the Neolithic-Eneolithic and Bronze Age extended from the steppe zone in the north to the desert zone in the south of Kazakhstan. In the Iron Age, remains of Equus hemionus became absent from the fossil record in the northern and central parts of Kazakhstan, thus suggesting a decreased range or abundance of the equid. This coincided with climate changes that occurred during the Bronze–Iron Age transition and the development of nomadic pastoralism. Since the Iron Age human societies in western and central Kazakhstan were predominantly nomadic herders, and livestock impacts on resources could have limited the wild ass distribution. An increased anthropogenic disturbance in 19–20 centuries could eventually have led to population decline in Asiatic wild ass and its extinction in the wild.

On the Status of the Boar Tooth Artifact from the Backdirt of Vogelherd

During the course of the excavations in the backdirt of Vogelherd in 2008, the crew recovered a tusk of a boar preserving clear signs of anthropogenic modification. In addition to the polishing that regularly occurs on tusks during the life of the animal, this specimen, showed signs of cut- ting, scraping and polish subsequent to the animal’s death. This artifact superficially resembles a Magdalenian female figurine with a triangular buttock and a stick-like torso, which led to the hypothesis that the find may be of Paleolithic origin and may be an artwork. Alternatively, the find was hypothesized to be an artifact of unknown function from the Holocene, based on the rarity of faunal remains of boar from the Paleolithic of the Swabian Jura. While the excavator always stressed the uncertainty related to the interpretation of the find, some colleagues ac- cepted the hypothesis that the find represented a Magdalenian female figurine. Thirteen years after its recovery, we have reexamined this artifact and conducted comparative studies that support the hypothesis that the find is of Holocene age. Based on similar finds, we conclude that, although the function of this class of artifact is not yet certain, this artifact is a Neolithic or Mesolithic tool with clear parallels in Germany, France and Switzerland. This class of artifact is rare in Central Europe, but our survey of Neolithic and Mesolithic publications allows us to reject the hypothesis, that this find represents a Magdalenian female figurine. This artifact, however, enriches the record of Holocene organic technology in southwestern Germany.