Quaternary Science Advances最新文献

The Pliocene to Holocene Kashmir basin of NW Himalaya, India, is prone to various geological and climatic hazards routinely connected to the climatic and structural setting of the Himalayan intermontane basins. The topographic expression of the basin is a direct consequence of the active plate tectonic convergence between the lithosphere plates of India and Eurasia. However, the role of the tectonic framework and its contribution to flood hazards has remained an unresolved research question. Our previous work has contributed towards this problem, and here, we extend our previous work by producing robust evidence in support of the role of active faults and tectonic topography in shaping the flood hazards in the Kashmir basin and its implication for the other similar basins in the world. The Landsat 8 Operational Land Imager-Thermal Infrared Sensor (OLI-TIRS) and Landsat 7 Enhanced Thematic Mapper Plus (ETM+) images were used to extract pre-2014 floodwater bodies and 2014 flooded areas in the Jhelum River valley of the Kashmir region, respectively. Water pixels were extracted using the modified normalized difference water index (MNDWI) methods, and similarly, the flood depth and duration (in days) were computed. The flood depth was correlated with the Jhelum River valley's topography, morphology, and geology. The slope and topography were also associated with the 2014 flood disaster to map the influence of the pre-disposed structural setting of the basin on flood vulnerability. The results suggest that flood disasters were mainly related to the unplanned built area, which remains the dominant factor in how flood hazards have turned into disasters. The results reveal the tectonically derived structural configuration of the basin mainly contributed towards the flood hazards, which is the primary predisposed structural framework to dictate flood hazards since the formation of the basin ∼4.0 million years ago. Therefore, the primary outcome of our work is the strong evidence that flood hazards are related to the structural setting of the basin, which includes topography and geology, while the transition of flood hazards into disasters is mainly because of unplanned urbanization.

Deltas are highly valuable environmental systems, ensuring various livelihoods through their ecosystem services. However, human impact and climate change stressors are impacting deltas immensely. Consequently, many deltas, including Ghana's Volta Delta, are facing increasing risks, especially as hazards are increasing in magnitude and impacting coastal livelihoods. To provide a better understanding of coastal hazards in the Volta Delta, this study assessed the Delta's subsidence regime and its consequences for the potential impact of sea-level rise (SLR). Using the Interferometric Synthetic Aperture Radar (InSAR) technique and Global Navigation Satellite System (GNSS) surveys, vertical land motion (VLM) was documented. Interferograms of Sentinel-1 data from 2016 to 2020 indicated subsiding rates of up to −9.2 mm/yr. By combining local VLM information with recent SLR projections and elevation data, this study updates those projections and provides local assessments of potential Relative SLR (rSLR) impact. According to these locally improved scenarios, up to ∼45 % of the Delta will fall below local sea level by 2100, of which close to 10 % is explained by the integration of local VLM data alone. Depending on the climate change scenarios used, land subsidence will increase the deltaic area at risk by 4.31 % (96.27 km²) to 10.18 % (227.64 km²) and consequently exacerbate its exposure to coastal inundation. To avert the projections, the study recommends robust monitoring regimes; alternative freshwater sources to groundwater; reduced sediment trapping and river obstruction; and the need to stall ongoing oil and gas prospecting and subsequent extraction in the Voltain Basin.

The spatio-temporal changes in the fluvial system and landform of the central Kachchh Mainland region are caused by distinctive ongoing tectonic deformations. The present study aims to decipher ongoing tectonic processes resulting modification of landscape in the Central Mainland Kachchh region during the Late Quaternary period. The region marks the presence of several neotectonic features along the faults indicating rejuvenation of the landform due to tectonic activity. The paleostress analysis of the faults indicates normal faulting due to WNW-ESE, E-W to WSW-ENE directed radial to pure extension. The OSL dates from the strath terrace section confirm accommodation of Quaternary sediments from ∼42ka till ∼32ka. The presence of abandoned channels and obstructed tributary channels across the fault plane deciphers reactivation of extensional fault planes at ∼42ka, constituting accommodation space for sedimentation on the downthrown block forming several sag-fill deposits. The sedimentation ceased after ∼32ka due to regional Kachchh Mainland Uplift (KMU) upliftment triggering vertical incision of channels forming several strath and fluvial terraces. The paleostress analysis and dynamic modification of landform depict reactivation of the hinge faults on the structural Mesozoic bend of the basement high known as the ‘Median High’.

Cave bears used caves for hibernation and giving birth. Caves maintain stable conditions of temperature and humidity, which facilitates the preservation of fossil accumulations. Causes of mortality in caves are related to starvation during hibernation, which affects mainly juveniles and old adults, predation and accidents, affecting bears of all ages. The Iberian Peninsula is located in one of the extremes of the geographical range of this species and has yielded an abundant cave bear fossil record, particularly in karstic systems in the northern fringe. The origin of the accumulation of bear fossil sites in Iberia has been investigated mostly based on selected paleobiological variables (sex-ratio and age-at-death profiles) and qualitative taphonomic assessment. The objective of this paper is to delve into the origin of a bear accumulation with a large proportion of hyaena remains, the Sima I of El Polvorín cave (Biscay, Northern Iberian fringe, Spain). For that end a combination of quantitative paleobiological (age-at-death and sex) and taphonomic (bone fracture patterns and surface modifications) data is used. This analysis has ruled out humans and hyenas as the origin of the accumulation but, due to the limited number of fossil remains available it is not possible to ascertain whether the bear accumulation was the result of a natural trap within the cave, natural mortality during hibernation, or a combination of both causes. This study underscores the necessity of integrated methodological approaches and the potential of old paleontological collections to provide new important paleobiological and taphonomic information under these approaches.

Postglacial vegetation colonization that followed ice retreat and proglacial lakes drainage in north-eastern America occurred rapidly, more rapidly than expected based on the modern dispersal capacities of boreal mixedwood trees. Paleo-islands from proglacial Lake Ojibway in Québec (Canada) were afforested early, before the final drainage of the lake. We hypothesized that these paleo-islands could have acted as outposts of migration and thus, could explain the rapid afforestation of lowlands observed. To determine if postglacial colonization occurred as a south-north front from the southern margin of Lake Ojibway or if islands acted as migration outposts, we estimated the date of first arrival of the main taxa of the current boreal mixedwood forest. We studied southern sites never covered by proglacial Lake Ojibway, sites that were islands within Lake Ojibway, and northern lowland sites that were liberated after the final drainage of proglacial Lake Ojibway. Taxa arrival was estimated as a sharp rise of the pollen percentage or as the occurrence of macro-remains within the sediments of small lakes dated with radiocarbon. Then we compared migration scenarios where colonization occurred gradually from south to north from the southern margin of proglacial Lake Ojibway and where paleo-islands of Lake Ojibway were first colonized through long-distance dispersal, thus becoming sources of seeds readily available to colonize lowland sites after the final drainage of Lake Ojibway. Finally, we compared the migration rates from the scenarios with the current mean dispersal capacities of the studied taxa. The migration rates estimated without taking the paleo-islands into account are too slow to explain the rapid afforestation observed following the final drainage of proglacial Lake Ojibway. Only the migration rates estimated from the scenarios with paleo-islands were comparable to the current mean dispersal capacity of the boreal mixedwood taxa. Thus, paleo-islands acted as stepping stones during postglacial migration, which explains why the lowlands were rapidly colonized. Larger paleo-islands and those located closer to the southern margin of the proglacial Lake were colonized first, in line with the theory of island biogeography.

Dating of gravelly fluvial deposits is typically hampered by the absence of suitable plant fragments for radiocarbon dating or sand layers for luminescence dating. Although gravelly fluvial deposits generally contain sand-sized quartz and feldspar that could be used for luminescence dating, the considerable grain-to-grain variability in beta dose rate, coupled with the lack of methods for routine dose rate estimation, presents challenges. In this study, a recently proposed model for calculating average beta dose rates in granular matrices was modified to be applicable to sand-sized dosimeter grains within gravelly deposits. We applied the modified model to sand-sized K-rich feldspars within sand matrices obtained from gravelly fluvial deposits in the Tokachi Plain, northern Japan, and compared the ages of samples obtained from sand matrices with those from sand lenses. Although the weight of <2 mm grains accounted for only 20%–35% of the bulk sediment, these grains were estimated to contribute approximately 70% of the external beta dose rate according to the model, because larger grains have a larger self-dose. Taking into account that the beta dose to dosimeter grains is mainly derived from smaller matrices (e.g. <2 mm), beta dose rates were also calculated based on the infinite matrix dose rate of the <2 mm fraction, along with the conventional water correction method. The ages of sand matrices calculated based on the beta dose rates derived from both the model and the infinite matrix dose rate of the <2 mm fraction were generally consistent with those of sand lenses. The dose rate calculated based on the model might be more accurate than that calculated using the infinite matrix dose rate of <2 mm fraction, but calculating the beta dose rate using the infinite matrix dose rate of <2 mm fraction is useful as a simple approach.

Thrusting supports the development of diverse landforms and deformational structures in the Himalayan Frontal Thrust (HFT) region between Kathgodam and the Chorgallia sector, according to this study. The influence of the active tectonic condition in the area was analyzed using seven geomorphic indices, which also underlined the importance of morpho-structural study utilizing remote sensing, geomorphic indices, tectono-geomorphic landforms, field evidence, and luminescence dating. The investigation of sub-basins surrounding the HFT reveals moderate to high tectonic activity, with tectonic activity concentrating in the eastern half and decreasing toward the west. A topographic discontinuity was also observed in the region as indirect active tectonic evidence. Hanging wall rocks have well-preserved features that govern tectonic transport direction, and the HFT in this region is emergent. Shear sense indications point to southerly tectonic migration, with a few modest northward shear senses indicating northward movement, which might be attributable to reverse thrusting along the HFT at some time during the Outer Himalaya's tectonic history. Petrographic investigations reveal sustained frontal deformation at various intervals, with well-preserved thrust-induced deformation fingerprints in deformed rocks throughout the Jam Raula and Sukhi nadi sections. Micro thrust duplexes, or micro-scale asymmetrical drag folds, are shown in thin section investigations as a result of HFT-related brittle-ductile deformation at moderate temperature and pressure. The sandy unit from the Quaternary sediments yields 10 ± 0.8 ka, 11.8 ± 0.7 ka, 17 ± 1 ka, and 56 ± 3 ka quartz OSL dates, demonstrating the migration of hanging wall rocks on footwall post-Siwalik fluvial deposits along the HFT plane and reactivation of the HFT in the study area.

Accurate and current rainfall analysis is crucial for planning and development in the new capital city of Indonesia (IKN). This study examines the effect of the Madden-Julian Oscillation (MJO) on rainfall variability in IKN using a 20-year dataset of Integrated Multi-Satellite Retrievals for GPM (IMERG) version 6 and automatic weather station (AWS) data. The study analyzes flood events in IKN by examining flood information provided by the National Agency for Disaster Countermeasures (BNPB) from 2008 to 2022 and the contribution of the MJO to these events. The findings indicate that the MJO significantly influences rainfall variability in IKN, with a more pronounced effect during the dry season (JJASO) than in the wet season (NDJFMAM). This is demonstrated by the higher occurrence of wet days and increased daily rainfall intensity, which is linked to extreme rainfall and longer-duration events, mainly between midnight and morning (0400–0600 LST). Notably, although floods are more common during the rainy season, the MJO can intensify flood events in IKN during the dry season. Therefore, when developing an effective flood disaster mitigation system for IKN, it is crucial to consider the amplitude and phase of the MJO.

Re-excavation of Ha Makotoko and Ntloana Tšoana rock-shelters in western Lesotho, produced abundant faunal remains (both macro and micro) from people using the Robberg technocomplex during the late Pleistocene (Ha Makotoko and Ntloana Tšoana (15.4–13.4 kcal. BP) and early Holocene (Ntloana Tšoana 11.1–10.2 kcal. BP). This faunal material allows us to identify the subsistence strategies they employed, using the unbiased Simpson's evenness index (1-D′), and Shannon's evenness index to track diet breadth. Detailed analyses of the sites' microfauna indicates that eagle owls and/or small carnivores — not humans — were responsible for introducing them into the deposits. A chi-squared test comparing diet breadth across the sites identifies hunting strategy, focused on size 2 and 3 migratory ungulates (equids, suids, and bovids), supplemented with size 1 and 4 bovids. Comparing the evenness values from Ha Makotoko and Ntloana Tšoana to published data from other Robberg-associated sites in the wider Maloti-Drakensberg region (Sehonghong, Rose Cottage Cave and Tloutle) allows variability in subsistence strategies to be addressed. A chi-squared test comparing ungulate size classes, small mammals and fish with the evenness index reveals two important statistical differences: the warm period occupation (16.5–14.3 kcal. BP) at Rose Cottage Cave presents a narrow diet heavily focused on size 3 ungulates (with a lack of fish). At the other end of the climate spectrum, cold conditions at Sehonghong immediately before the Last Glacial Maximum were associated with a narrow diet focused on intensive fishing, with lower-than-expected numbers of size 3 ungulates. The deposits at Ntloana Tšoana, Ha Makotoko, and Tloutle, along with the Younger Dryas-associated assemblage from Sehonghong, on the other hand, present broad diets. Fish and small mammals make more of a contribution to the expanding diet in the highlands. Our approach demonstrates the flexibility that makers of Robberg tools displayed in adapting to the changing climatic and ecological conditions of this high-elevation region in the interior of southern Africa during Marine Isotope Stage 2 and across the Pleistocene/Holocene transition.

In the Himalaya, natural hazards are common and their places, as well as timings, are difficult to predict. Rough terrain, unpredictable weather conditions and poor road networks of the Himalaya make the mitigation measures even more challenging as well as difficult. On April 4, 2023, 7 people have died and 13 were injured due to a small loose snow avalanche at 14th Mile, on the way to Nathula Pass, near Indo-China Border in Sikkim state (India). State government had advised the people, not to visit the area due to the poor weather conditions. However, people have ignored this precious advice and lost their lives. Along with Indo-China border, the region is famous for its scenic beauty. In addition, the region is one of the most difficult border areas with the limited infrastructural development for armed forces. The present study explores the causes and consequences of this killer avalanche from an environmental determinism. The results suggest that, due to the western disturbances, the region received heavy snowfall. Higher average temperature and flowing stream beneath snow, make the snow unstable. Weight of humans put pressure on the weak snow which led to formation of avalanche. Our finding suggests that peoples’ negligence about government advices have led to casualties. The purpose of this case study is to highlight the human folly which invites such unfortunate incidences across the globe. Further, this study emphasis the need of public-government partnership to minimize the impact of such upcoming hazards.