Quaternary Science Advances最新文献

Unraveling how Global Mean Sea Level (GMSL) fluctuated during past warm periods can improve our understanding of linkages between sea-level fluctuations, orbital forcing, and ice-sheet dynamics. Current estimates of GMSL for Marine Isotope Stages (MIS) 5a and 5c — two warm intervals following the relatively well-documented MIS 5e — contain meters of uncertainty and fewer data due to several challenges. These challenges include concealment of datable in-situ coral facies by MIS 1 deposits and inaccessibility due to submergence by modern sea level. We present a comprehensive dataset based on U–Th dating and stratigraphic correlation of 23 cores totaling over 170 m of recovered coral-reef deposits across the tectonically stable Florida Keys Reef Tract (FKRT). Following detailed facies descriptions, 34 in-situ, minimally altered aragonitic coral samples (≤2.7% calcite) below the Holocene-Pleistocene boundary were targeted for U–Th geochronology. Fourteen closed-system coral U–Th ages from MIS 5a include the commonly used sea-level indicator Acropora palmata, but also the massive coral taxa Pseudodiploria strigosa, Siderastrea siderea, Orbicella spp., and Porites astreoides. Dating yielded ages in the range of 88–81 ka (average 2σ uncertainty of less than 200 years). These ages suggest MIS 5a reef initiation at ∼88 ka BP, a peak near 83 ka with minimum elevations between −6.0 ± 0.5 and −5.6 ± 0.5 m MSL (2σ uncertainty and subsidence-corrected), and reef termination and sea-level fall by ∼81 ka BP. Notably, the range of peak MIS 5a relative sea-level estimates of −6.5 to −5.1 m MSL are more than 2 m shallower (higher) than previous estimates of −11 to −9 m. Our higher resolution regional sea-level reconstruction across four subregions of the Florida Keys reef tract aligns with changes in July insolation at 65° N: a trend that most other records, such as deep-sea sediments, do not have the accuracy and precision to resolve. Three massive coral samples from MIS 5c, consisting of Pseudodiploria clivosa, and Orbicella spp., yielded ages in the range of 104 to 99 ka (average 2σ uncertainty less than 200 years); however, because only one sample met the closed-system criteria, our ability to estimate MIS 5c sea level is relatively limited. More empirical estimates of sea-level from the MIS 5a and MIS 5c intervals based on numerical dating of reliable local sea-level constraints are critical for GMSL calculations and relating changes in sea-level amplitude and timing to global ice volume modeling and glacio-isostatic effects, all of which can improve predictions of future sea-level changes in coastal regions.

A growing number of authors have discussed the role of climate change in periods of important biological and cultural transition along the hominin lineage. This paper establishes a biocultural framework elucidating human behavioural adaptations during the African Early and Middle Stone Age, centred on three crucial dimensions of hunter-gatherer adaptation: mobility, social network dynamics, and technology. We contend that landscape properties, specifically resource diversity and seasonal to inter-annual resource variability, can be used to model the specific responses of hominin groups to climate change over time, based on their awareness of these properties. Specifically, we focus on hominin technological generalisation and specialisation, meaning the extent to which there is a high degree of specificity (or fit) between final tool form and the task(s) in which the tool is deployed.

In this regard, we argue that the archaeological record reveals punctuated and discontinuous specialisation during certain phases of the Early Stone Age driven by landscape predictability. These periods encourage the expression of relevant innovations and stepwise increases in technological complexity. While some of them become lost to demographic or cultural stochasticity, others end up forming the basis for a standardisation of generalised forms within the context of unexpected climatic deterioration. This is highlighted by the late Acheulean: following a period of greater generalisation in the late Early Pleistocene correlating with repeated and severe orbitally-forced periods of aridity, smaller biface forms become more common (or absent) and regional experimentation with prepared-core technology in Eastern Africa takes place in the context of a return to more humid and stable climatic conditions. The onset of more arid and variable climates associated with the emergence of the Middle Stone Age led to the continental expansion of the prepared-core technological substrate underpinning generalised assemblages. The cycle continues in the Middle Stone Age with a return to climatic stability in the Late Pleistocene and subsequent regional diversification of this techno-complex, in which hominins responded with greater toolkit specialisation in a number of different ways. In this context, we support the existence of a cyclical and non-linear relationship between environmental adaptation and cognitive evolution, as part of a wider biocultural feedback loop, which contributes to explain the evolutionary roots of our “generalist specialist” niche.

An integrated geophysical and geotechnical study evaluated the foundation conditions at the War dam site in northwest Ethiopia. This investigation included the classification of rock quality, shallow seismic refraction, and magnetic approaches. The dam's location comprises quaternary soil deposits and rhyolite rock units that have undergone varied weathering and fracturing. The shallow seismic refraction method distinguishes three layers of p-wave velocities that are less than 1.5 km per second with a depth range of 2–6 m, 1.5–2.5 km per second at a depth range of 15–20 m, and 2.5–3.5 km per second ranging from 20 to 40 m, respectively. Magnetic data were used to identify lineaments, and the RQD value acquired from boreholes ranged from extremely poor to excellent. Lineaments were recognized using the tilt angle approach. The results of the permeability tests demonstrated that the rock mass that serves as the dam's foundation had characteristics that are resistant to low permeability. The maximum and minimum lugeon values obtained from the testing were 9Lu and 0.81Lu, respectively. There are weak zones at and below the surface of the dam site, according to the overall findings acquired from seismic refraction, magnetic, and discontinuity surveying. These results were obtained from monitoring the dam site. These significant structures are directed towards a SW-NE, NE-SW, NNW-SSE, and SSW-NNE orientation. The study assessed the geological suitability of a proposed dam site using seismic refraction and magnetic survey methods. Significant geological variations were observed, particularly in the right abutment and valley floor, indicating the need for targeted grouting. The findings suggest that while the site is generally suitable for dam construction, specific areas require further ground improvement to ensure stability.

Landslides account for the breakdown of natural topographies, impacting many mountainous areas and leading to loss of lives and damaged infrastructure. This research aims to generate a reliable landslide susceptibility zonation map employing geospatial and Analytical Hierarchy Processes (AHP) in Addi Arkay Woreda, North Gondar Zone, Amhara Regional State, northern Ethiopia. The present study uses remote sensing data, geographic information system (GIS) tools, AHP, and weighted linear combination (WLC) models to analyze multiple environmental variables, including slope, aspect, curvature, lithology, soil texture, topographic wetness index (TWI), and rainfall. As per the results, around 186.12 km² (13.26%) of the total study area is under very high landslide susceptibility and 140.85 km² (10.05%) under very low susceptibility. Using Google Earth images for inaccessible areas, 121 landslide inventories were identified through fieldwork. Of these inventories, 85 were used to train the model and 36 for testing. The performance of the AHP model was validated by the Receiver Operating Characteristics (ROC) curve (0.75), which indicates good predictive accuracy for identifying landslide-prone areas. These findings are essential to regional land use planning, hazard mitigation, and landslide prevention efforts. Additionally, this study contributes to the scientific understanding of landslide dynamics in the Northwestern highlands of Ethiopia and offers a methodological framework that can be applied to other regions with similar geological and climatic conditions.

In Africa south of the Zambezi River, archaeologists and other experts have long explored the impact of climate and environmental changes to the development of ancient civilizations during the Iron Age (CE 200–1900). Some of the prevailing thought is however still rooted in environmental deterministic models informed by selected ethnographies, stable isotopes and archaeological evidence. For instance, the drought brought by the medieval Little Ice Age is assumed to have collapsed the civilisation at Mapungubwe in the Shashi-Limpopo valley around 1300 CE. And yet, within the wider region, and in similar ecological settings, upstream (Shashi and Upper Limpopo) and downstream civilisations (Lower Limpopo), persisted and thrived through the same climatic challenges. We draw on African cosmologies, resilience theory and archaeological evidence from Mapela and Little Mapela to spotlight adaptation strategies utilised by their inhabitants to build resilience through time. The main conclusion is that even in cases of climatic extremes, humans responded to opportunities and constraints in context specific ways.

Rupture behaviors of a subduction megathrust define the slip type, the extent and the associated tsunami hazard. They are, however, difficult to be defined precisely due to limited fault-zone observations. Here, we integrate GNSS, tsunami-waveforms, seismic-profiles, and earthquake-cycle modeling to delineate the slip-extent of the 2020 M_w 7.8 Simeonof and the 2021 M_w 8.2 Chignik earthquakes in the Semidi segment; and to understand the possible structural and mechanical control on the distinct rupture behaviors of this segment and its neighboring Shumagin segment at the Aleutian-Alaska subduction zone. We show that both the Simeonof and Chignik earthquakes slipped a compact area at depth between ∼20 and 40 km that is well constrained by the combination of GNSS and tsunami-waveform data. We explain the distinct slip behaviors associated with the Semidi and Shumagin segments by highlighting the morphological changes in the fault along the strike direction. Beneath the Shumagin Island, we identify a structural-mechanical boundary that separates the megathrust into Semidi (east) and Shumagin (west) two segments. Semidi is gentle and curved; while Shumagin is steep and planar. The Semidi segment produces spatially-heterogenous stress field, and generates partial, full, complex ruptures as indicated in modeled cycles and in historical seismic observations. Meanwhile the Shumagin segment, coincides with the ocean-continent transition boundary – the Beringian margin, tend to generate slow-slip-events, tremors, otherwise, generates small or moderate seismicity as indicated in the modeled cycles and in seismic records since 1750. Our findings indicate that Semidi is likely to rupture in a chaotic fashion with major or large earthquakes, resulting a greater tsunami hazard like the 1938 M_w 8.2 event. The tsunami potential in the Unimak segment may also remain high.

Quantifying ecosystem resilience under drought is crucial for sustainable development strategies. This study aims to investigate the spatial and temporal variability of Net Primary Productivity (NPP) across anthropogenic biomes in India (2000 to 2020) and to understand the post-drought long-term ecosystem resilience. A time series study of monthly precipitation, standardized precipitation index (SPI), and NPP were applied to understand ecosystem resilience across twenty anthropogenic biomes. Mann-Kendall test was used to quantify the magnitude and direction of the trend. In addition, bivariate raster maps of mean precipitation and soil moisture were presented in relation to ecosystem resilience in India. The forested areas in the Himalayan region and the Western Ghats of India were identified with resilient ecosystem that can withstand climate change. However, the croplands and rangelands were non-resilient to drought, making them vulnerable to climate change. Northern and western part of India falls under catastrophic to critical non-resilient ecosystem. Soil moisture availability in the biome, forest cover, type of land use, agricultural practices, and climate shocks are mainly influencing the resilience of the anthropogenic biomes in India. The resilience assessment can be used by policymakers to plan anthropogenic interventions in harmony with nature.

Landslides are prevalent in the Ethiopian highlands, particularly in the east Gojjam zone, which is highly affected by landslide problems. This research was carried out in the east Gojjam zone, northwestern Ethiopia. The study area is part of an economically important area in the country, and it is the main source of water for the Grand Ethiopian Renaissance Dam (GERD). The main objective of this work was to undertake a detailed inventory of past landslide locations and prediction of present and future landslide hazards, as well as the preparation of a landslide zonation map in the East Gojjam zone by using the Analytical Hierarchy Process (AHP) with the GIS technique. The parameters used for this study were slope degree, slope aspect, land use and land cover, road proximity, rainfall, lithology, altitude, and river proximity. The various causative parameters were collected from the field, and suitable modifications were made to the thematic maps. Finally, the ratings for various parameters were used as the basis to prepare the LHZ map in GIS windows. The landslide susceptibility and inventory mapping were produced in the GIS environment. The results of the study show that the main driving factors for the landslide hazards in the area were river proximity, rainfall, and manmade activities. Validation of this LHZ map revealed that more than 80% of past landslides match within the "high hazard zone" and reasonably accepted the rationality of the adopted methodology. The considered parameters, as well as their evaluation of the production of LHZ-Map, were confirmed. The produced landslide inventory map is very important for urban planners, agricultural studies, environmentalists, and future landslide hazardous prevention and mitigation strategies.

Flooding is a severe meteorological event that can result in fatalities and major economic losses. This study utilizes geographic information system, remote sensing technology, and multi-criteria decision making to create an accurate flood susceptibility map for the Melka Soda district in Southern Ethiopia. Various factors such as normalized difference vegetation index, landuse landcover, soil type, drainage density, slope, rainfall, geology, and elevation were taken into consideration when mapping out areas susceptible to flooding. The results indicate that 7.1%, 16.6%, 20%, 29.9%, and 26.4% of the district are classified as very low, low, moderate, high, and very high hazard zones, respectively. By analyzing population density and land use in conjunction with the flood hazard map, five zones of varying risk levels were identified: very low, low, moderate, high, and very high-risk zones covering 12.4%, 29.5%, 39%, 10.6%, and 7.5% of the district respectively. This showed that 18.1% of the district is classified as having a high to very high level of flood risk. To validate this result, survey data was used to map 28 flood points in the area, and a receiver operating characteristic curve was plotted, resulting in an area under the curve of 86.7%. This confirms the accuracy of the proposed framework, which can assist authorities in creating development policies that consider the current flood risk in the area.

The directly dated RRMarch2021 age model (Roberts et al., 2021) for the ∼293 m long composite core from Chew Bahir, southern Ethiopia, has provided a valuable chronology for long-term climate changes in northeastern Africa. However, the age model has limitations on shorter time scales (less than 1–2 precession cycles), especially in the time range <20 kyr BP (kiloyears before present or thousand years before 1950) and between ∼155 and 428 kyr BP. To address those constraints we developed a partially orbitally tuned age model. A comparison with the ODP Site 967 record of the wetness index from the eastern Mediterranean, 3300 km away but connected to the Ethiopian plateau via the River Nile, suggests that the partially orbitally tuned age model offers some advantages compared to the exclusively directly dated age model, with the limitation of the reduced significance of (cross) spectral analysis results of tuned age models in cause-effect studies. The availability of this more detailed age model is a prerequisite for further detailed spatiotemporal correlations of climate variability and its potential impact on the exchange of different populations of Homo sapiens in the region.