Quaternary Science Advances最新文献

Nitrate uptake is an essential nutrient for primary production. A study focused on the surface waters of the Bay of Bengal (BoB), new, regenerated, and total production were estimated from nitrate, ammonia, and urea (nitrogen uptakes). Understanding nitrogen uptake rates in coastal waters, where nutrient limitations can disturb environmental biological productivity, is essential. A detailed study of these uptake rates and metabolic processes is required to develop effective mitigation strategies to prevent further degradation of these ecosystems. Total production ranged between 1.39 and 7.43 mmol N m² d⁻¹, new production ranged between 0.58 and 2.83 mmol N m² d⁻¹ and regenerated production ranged between 0.83 and 4.59 mmol N m² d⁻¹. The study observed a significant negative correlation nitrogen uptake along with pH, sea surface salinity (SSS), and sea surface temperature (SST) was observed in the study. The R² values for SST were 0.605, 0.619, 0.503, 0.601, and 0.627; for SSS they were 0.688, 0.511, 0.498, 0.579, and 0.644 with nitrogen (Na¹⁵NO₃), ammonium (¹⁵NH₄Cl), urea (CO(¹⁵NH₂)²), regenerated, and total production uptake, respectively. pH was highly correlated with nitrate uptake (R² = 0.525), had a low correlation with ammonium uptake (R² = 0.439) and a moderate correlated with urea uptake (R² = 0.526). A positive relationship of nitrogen uptakes with chlorophyll-a, dissolved oxygen, and dissolved inorganic nitrogen (DIN) were observed. Chlorophyll-a had R² value of 0.608, 0.126, 0.524, 0.526, 0.578, with Na¹⁵NO₃, ¹⁵NH₄Cl, CO(¹⁵NH₂)², regenerated and total production uptake respectively. Dissolved oxygen (DO) related to ammonium uptake showed a very poor correlation (R² = 0.079) but a better correlation with urea (R² = 0.534). New production uptake rate showed a high positive correlation with DO (R² = 0.645), whereas regenerative production uptake rates showed a relatively low correlation (R² = 0.519). The positive relationship between DIN and nitrogen uptake had corresponding R² value of 0.642, 0.591, 0.558, 0.652 and 0.675 for nitrite, ammonium, urea, regenerated and total production uptakes respectively. Total nitrogen: Total phosphate (TN:TP) showed a positive correlation with ammonium. The TN:TP relationship fit nicely with R² = 0.576 (nitrate uptake), 0.524 (ammonium uptake), and 0.503 (urea uptake) in the coastal BoB. Hence, by applying statistical analysis, principal component analysis and pearson correlation, the interdependency of the environmental parameters enhancing the new production has been confirmed.

A revaluation of the relative sea-level (RSL) indicators in the Baia di Infreschi (Cilento, Southern Italy) supported by new 30 U/Th dating on speleothems indicates that the upper level of Lithophaga burrows identified by Bini et al. (2020) at ∼9 m a.s.l. and correlated to the Last Interglacial (LIG) highstand should be referred to the highstand of the MIS 9e, whereas the local RSL for the highstand of the LIG is now reassessed at 5.3 ± 0.18 m a.s.l. The upper level of the Lithophaga marker can be followed for ∼12 km along the coast, suggesting a substantial absence of important relative tectonic movements. In the Baia di Infreschi an additional marine indicator, a notch sealed by a flowstone dated ∼110 ka, indicates several phases of RSL stationing below the maximum highstand of the LIG. The presence of flowstones as low as 2 m a.s.l. dated to the MIS 7 shows that the highstand of MIS 7 was probably below the present sea level. All these evidences allow us to reassess the stratigraphy of some archaeological caves in the area, indicating that the sedimentary successions preserved there are older than what was previously believed.

This paper addresses the interplay between Holocene landscape evolution and human settlement dynamics, drawing new evidence from the alluvial history of Xerolakkos, a continental stream in Grevena (Western Macedonia, Greece). We developed an integrated geoarchaeological survey combining remote sensing geomorphological mapping, litho-stratigraphic analysis and radiocarbon dating with the site evidence of a new archaeological survey. Results revealed four major alluviation phases, corresponding to 1) the beginning of the Holocene until the Early Neolithic (∼6300/6200 BCE), 2) the end of the Early and the Middle Neolithic (∼6000–5400 BCE), 3) from the Middle Bronze Age to the Late Roman period (∼1800 BCE – 500 CE), and 4) during the Byzantine and Ottoman eras (∼500–1800 CE), all separated by phases of floodplain incision. Furthermore, the effects of several Holocene Rapid Climatic Changes (RCC) are traced and discussed together with potential human responses; we also provide the first alluvial sequence recording the ∼6200 BCE (8.2 kyr BP) event in the Balkans. While the climate and the local geomorphological setting are considered the primary drivers behind instability and erosion during the Early and Middle Holocene, a landscape change starting in the Middle Bronze Age (after ∼1800 BCE) followed by a re-organisation of the rural economy in the Roman period suggests the increasing involvement of anthropogenic forcing which, by the Ottoman period, evolved into a dynamic situation between climatic variability and adaptive land management. Finally, we demonstrate how soil erosion in the upper catchment constitutes a serious taphonomic bias when studying the regional archaeological record.

This investigation was conducted in southern Ethiopia's Maze watershed in the Omo River Valley. Frequency ratio (FR) and analytic hierarchy process (AHP) techniques were used to assess landslide susceptibility in the region. Identifying causative components and landslide inventory data achieved the goal. Remote sensing and on-site investigations found 793 landslide polygons. To assess vulnerability, the landslide inventory information is categorized into two groups: the training dataset (70%) and the validation dataset (30%). This study examined “slope, aspect, curvature, lithology, land use and cover, normalized vegetation index, and proximity to fault lines, rivers, and distance to road as landslide controlling factors”. The spatial analysis capabilities in Arc GIS were used to overlay the weights of all landslide-causing components to create the susceptibility map. A final landslide susceptibility map is produced using FR and AHP methods and categorized as “very low,” “low,” “moderate,” “high,” and “very high.” The frequency ratio method divides the region into susceptibility classes by frequency. The very low, low, medium, high, and very high susceptibility groups cover 25%, 20%, 18%, and 19% of the territory. The analytical hierarchical process technique shows that 3%, 7%, 26%, 36%, and 28% of the area are very low, low, medium, moderate, and very high landslide susceptibility. The receiver operating characteristic curve was employed to validate the area-underlayer susceptibility maps. The success rates were determined using the FR and AHP approaches, resulting in AUC numbers of 0.873 and 0.87. Similarly, the prediction rates were determined to be 0.81 and 0.80. The landslide susceptibility maps will significantly influence land resource allocation.

A study was conducted to decipher changes in paleoenvironmental conditions of the Kashmir Valley (India) using stable isotopic compositions and elemental concentrations of total organic carbon (TOC) and total nitrogen (TN) in a sediment core from the Wular Lake. The Chronology of the core established through radiocarbon dating estimated the age of the core bottom to be 3752 Cal years BP, covering the late Holocene. Using carbon isotopic compositions of TOC (δ¹³C), nitrogen isotopic compositions of TN (δ¹⁵N), and TOC - TN contents, the study identified changes in biology and associated biogeochemical processes in the Wular Lake during the late Holocene. Changes in C and N biogeochemistry of the lake through the last 3752 Cal years BP suggested overall drier condition during 3752–1500 Cal years BP that transitioned into a wetter condition at around 1500 Cal years BP until at least 295 Cal years BP. Evidence for relatively intense drier events were observed within the dry and wet phases at around 2500 and 500 Cal years BP. Changes in δ¹³C and TOC contents in the sediment core revealed that the inorganic C dynamics and productivity (along with organic C contents) in the lake were largely regulated by variations in respired CO₂ and HCO₃⁻ availability along with terrestrial matter supply through the Jhelum River. Similarly, variations in δ¹⁵N and TN contents showed changes in N dynamics of the lake with varying nitrification and decomposition throughout the studied period. Observed dry and wet phases in the region might be due to the weakening and strengthening of the precipitation, which was linked to negative and positive phases of the North Atlantic Oscillation, respectively.

This paper examines the interplay of environmental change and human demographic shifts among late Pleistocene and Holocene populations in the hyper-arid context of the Central Namib Gravel plains, Western Namibia. This paper applies a structural equation modeling (SEM) approach to arid-zone hunter-gatherer mobility patterns and settlement systems based on variability among ethnographically and historically observed groups. It then applies this model in examining issues related to the Middle-to-Later Stone Age transition at the sites of Erb Tanks and the Mirabib rock shelter. This model suggests that, among modern arid-zone foragers, population density is by far the strongest factor influencing mobility and settlement systems, with higher population densities favoring longer residential site usages and shorter residential moves within smaller territories. In contrast, environmental variables having to do with annual rainfall, rainfall seasonality, and effective temperature affect mobility and settlement systems in ambiguous and statistically insignificant ways. This paper closes by arguing that regional-scale population increases signaled by various features of Later Stone Age archaeological patterning led to local population expansions in the Central Namib Desert, and that this in turn caused a range of recognizable cultural shifts that were strongly linked with adaptations to aridity.

The authigenic ¹⁰Be/⁹Be dating method presents a valuable tool for reconstructing depositional chronologies in sedimentary environments, requiring only ubiquitous mud for sampling. Nevertheless, studies elucidating the variability of the ¹⁰Be/⁹Be record preserved in epicontinental successions are lacking, despite the essential nature of such knowledge for the application of authigenic ¹⁰Be/⁹Be in geochronology. In this study, we investigate the variability of measured natural ¹⁰Be/⁹Be ratios in sediment cores recovered from the Holocene Po River delta plain in Northern Italy, aiming to unveil the influence of changing sedimentary environments and provenance on the beryllium isotopic signature. We identified significant variations in the authigenic ¹⁰Be/⁹Be ratios across parasequences, which correlates with a provenance change from the Eastern Alps to the Po River. The observed variation would cause an age offset of ∼1 Myr if unrecognized in a dated succession. Our analysis revealed consistent ratios between the delta plain (primarily represented by swamp) and delta front consisting of proximal prodelta facies, suggesting a prevalent riverine signature in the proximal prodelta, likely maintained by hyperpycnal flow deposition. Statistical assessments based on random sampling and bootstrapping highlighted the importance of a sample size of n > 10. Furthermore, a standard deviation of the observed variability indicates a necessity of an additional 9% uncertainty in authigenic ¹⁰Be/⁹Be dating studies if the sample size is smaller. Overall, our findings emphasize that the normal regressive highstand settings of a deltaic system maintain relatively stable beryllium isotopic fluxes, which are favourable for the authigenic ¹⁰Be/⁹Be dating application, if provenance changes are known.

The region of the Himalayan arc covering Sikkim and eastern Nepal experiences dominant strike-slip deformation oblique to the convergence direction of the Indian plate. This region is also traversed by transverse structural and tectonic features. The present study is aimed at comprehending the horizontal and vertical deformation rates for this region using the PSInSAR technique. We utilized 70 and 78 Single Look Complex images in ascending and descending passes respectively, spanning from February 2017 to August 2023 for time-series displacement measurement along the radar line of sight (LOS). The results reveal the LOS velocity ranging from −15 to +10 mm/yr for the ascending data and ±20 mm/yr for the descending data. The mean line-of-sight velocities of ascending and descending passes were decomposed to estimate the horizontal (east-west) and vertical components of the deformation vector. These components range from ±15 mm/yr and −12 to +8 mm/yr, respectively, suggesting that the horizontal deformation predominates in the study area. A NW-SE trending boundary coinciding with the Tista lineament sub-divides the study region into the eastern Nepal and the Sikkim blocks based on the patterns of the deformation rates. The eastern Nepal block south of the Main Central Thrust exhibits locked portion of the arc with eastward motion, whereas the Sikkim block exhibits uplift (unlocked with creep) and westward motion. The amplitudes of these deformation rates support dominant strike-slip deformation with minor vertical deformation component. These results suggest that the Tista lineament is a prominent strike-slip fault and probably the most significant active tectonic feature in the region. Together with the seismicity data, we infer that probably the entire crustal block rather than the Himalayan wedge is contributing to the surface deformation, as mapped by the present PSInSAR study.

A Mid-Late Holocene palynological and charcoal record of vegetation and climatic changes in the tropical rainforest of West Africa is presented based on sediment cores from four localities in southwest Nigeria. The localities namely Ahanve, Ogudu, Otolu-Lekki and Ikorigho are situated along gradients in riverine and coastal systems that drain into the Atlantic Ocean. The aim was to reconstruct the vegetation history of the tropical rainforest, infer past climate variabilities and ascertain the presence of humans and their impact on the landscape. The record shows that the Mid Holocene, c.6600-5600 BP, was characterised by predominantly diverse and extensive tropical rain forests that comprised lowland rainforest, mangrove swamp forest and freshwater swamp forest that are consistent with the African Humid Phase (AHP); climatic conditions were warm and wet with high sea levels. In the early stages of the Late Holocene, there is evidence of decline in the tropical rainforests with brief spells of climatic variability signalling the gradual end of the AHP. Subsequently, the pollen record revealed evidence of forest disturbance: specifically the replacement of the mangroves and lowland rainforests by coastal savannas and an Elaeis guineensis-dominated secondary forest, respectively, in Ahanve at cal. 3100 yr BP; and the decline and eventual recovery of the vegetation types in Ogudu after cal. 2760-2730 yr BP. These environmental disturbances are attributed to prolonged period of increased desiccation within a warm climate as well as the differentia in marine and riverine influence of both localities. Further decline in the tropical rainforest after cal. 1240-1200 yr BP were accompanied by substantial increase in oil palm (Elaeis guineensis), the emergence of exotic plants of South American and Asian origin, substantial increases in charcoal particles that were complemented by archaeological data. The pollen and charcoal data have shown that the decline of the tropical rain forests in the area beginning from the late Holocene was initially climate driven while subsequent and recent decline has been exacerbated by anthropogenic factors.

Landslides occur when debris, rocks, or soil particles move downward. Examining the susceptibility of landslides is essential for safeguarding human well-being and assessing the consequences of landslides on the natural surroundings and ecosystems. This study utilized the frequency ratio technique to evaluate the probability of landslides happening in the Kulfo River watershed, situated in the Rift Valley area of Ethiopia. In order to ensure a comprehensive analysis, many data sources were employed, including satellite images, geological data, and historical records of landslides. This study developed a systematic approach to assess the probability of landslides by considering ten (10) influential factors: land use/land cover, slope, aspect, elevation, curvature, lithology, proximity to lineament, and normalized difference vegetation index (NDVI). The ten influential elements were prioritised based on literature review, expert knowledge, and preliminary study area analysis. The aforementioned causal elements are integrated with a comprehensive landslide inventory map. The sensitivity of the study's area to landslides was mapped using a frequency ratio (FR) model. Subsequently, it was classified as representing various degrees of vulnerability, spanning from extremely minimal to quite significant. The effectiveness of the suggested model was measured by evaluating the accuracy of the generated map of landslide susceptibility by the area under the curve (AUC) technique. Based on the most recent study results, the success rate curve has an area under the curve (AUC) of 79.6%, which indicates a highly satisfactory level of performance. Policymakers may utilize the findings of this study to make educated decisions on how to mitigate the risks of landslides in relation to land use and preparedness for disasters.