Quaternary Science Advances最新文献

Comprehending the nature, extent, and distribution of seismogenic structures, along with their seismogenic potential to induce destructive earthquakes in low seismic strain regions, holds significant socio-economic significance. Analyzing historical and paleoearthquakes becomes essential to understanding the influencing factors controlling the origin of earthquakes in intraplate regions, such as the Korean Peninsula. Based on current knowledge, the seismic pattern within the intraplate region, particularly along the Korean Peninsula, exhibits greater heterogeneity. This observation is drawn from historical seismic records, instrumentally detected seismic patterns, and paleoseismological analyses. Comprehensive paleoseismological studies play a crucial role in providing new evidence for fault activity, and hence they are an important contribution to the understanding of the seismic and structural evolution of faults. Existing paleoseismic investigations have predominantly focused on southeastern Korea, primarily along the Yangsan or Ulsan faults, with less attention given to other faults in the southeastern part of the Korean Peninsula. In the ongoing Korean Active Fault Mapping Project, this study specifically identifies a fault trace approximately 5.5–7 km long along the Ulsan-Dongnae Fault system named as Seokgye fault, named after the locality. Detailed paleoseismic investigations were carried out along the Seokgye fault. The fault presents a clear example of fault reactivation under the present compressional tectonic setting with a paleoearthquake during the late Pleistocene (∼121 ± 6 ka). Based on the length of the fault traced and observed displacement in the trench, Seokgye fault is capable of generating an earthquake of magnitude similar to the 2016 Gyeongju earthquake (Mw 5.8). This research enhances our understanding of the ongoing tectonic processes and Quaternary activities of fault systems in the southeastern Korean peninsula. Additionally, it contributes valuable insights for local-scale seismic hazard analysis in the area.

The western part of the Indian plate, which includes three major paleo-rifts, the Kachchh, Narmada and Cambay basins, is tectonically active and has seen moderate to large earthquakes. Regional stress due to the convergence of the Indo-European plates is the main cause of deformation accumulation in this section. However, a number of local strain accumulation factors within the plate also appear to be responsible. In the present study, we conducted GNSS-based deformation analysis along the Cambay Rift-Basin and Narmada Rift Basin (CRB and NRB) using GNSS datasets spanning over a decade (2009–2020). An average deformation of ∼1.2 ± 0.2 mm/year and a maximum strain of 2 × 10⁻⁰⁸ strains/year are associated along these two ancient rift systems. The cross and along motion of GNSS sites relative to the NRB indicates dextral movement along the CRB. Furthermore, the motion of GNSS sites was analyzed to see the motion along these two rift systems and prepared a schematic model to understand the genesis of earthquakes in the study area. We found two locations of maximum stress accumulation in the study area. The stress distribution as well as the local geological structures are the main causes of stress accumulation and seismicity in the northern part of the CRB. The stress acting from the north and south form a compression zone along the NRB. GNSS derived strain analysis indicate accumulation of extensional strain towards the northern part of the CRB and therefore, generating dip-slip as well as the strike-slip earthquakes in the region. The study recognizes the role of lineaments, Paleo-rift margins as well as geological trends and fold systems in the present-day seismo-tectonics of Western India.

The Coseismic Ionospheric Disturbances (CID) due to the 26th December 2004 earthquake of Mw 9.2, which occurred in the Sumatra-Andaman subduction zone, are analyzed using cGPS-aided Total Electron Content (TEC) measurements. For the CID analysis, data from nearby seven Sumatran GPS Array (SuGAr) and two International GNSS Stations (IGS) located to the south of the epicenter, at a distance of 500–1000km (near-field) and two IGS stations located to the north-west of the epicenter at a distance of 2000km (far-field) are considered. The CIDs with a propagation velocity of 595–694m/s arrived within 2–10min after the earthquake, depending upon the distance of a station from the epicentre. Variations in the CIDs can be prominently seen at the nearest cGPS Station SAMP immediately after the earthquake. NTUS, being the farthest station shows some small variations. The delay in the occurrence of variations at GPS sites can also be associated with rupture propagation. Because all the stations used in our analysis are located south of the epicenter and rupture of the earthquake propagated in the north, the trend of rupture propagation could not be analyzed clearly.

The morphological characteristics and distribution of volcanic cones of Jeju Island in Korea could be controlled by several factors, including stress field in the substrate and subsurface fractures. Controlling fractures, however, might not be visible on the outcrop in volcanically active areas like Jeju Island, because of the layer of volcanic rocks covering them. Furthermore, inferring the paleostress is much more difficult. Hence, it is essential to identify the concealed feeding fractures through an indirect approach based on a morphometric analysis. Thus, Jeju Island is one of the best places to study this issue. Measurements of ellipticity, maximum crater diameter, breaching azimuth, coeval cone alignment, and the line connecting depressed points on 152 Quaternary volcanic craters, were taken to identify magma-feeding fractures. Jeju Island in SW Korea comprises Quaternary volcanic rocks overlying the Tertiary ∼ Quaternary sediments of the Seogwipo Formation, Tertiary unconsolidated sediments (U Formation), and Cretaceous granite. This study identified two dominant types of Pre-Pleistocene magma-feeding fractures including E-W and NE/ENE-trending fractures consistent with previously identified Pre-Neogene E-W and Miocene NE-trending fractures around Jeju Island. These fractures might be associated with the rotation of maximum horizontal stress direction (σ_Hmax). Identifying subsurface structures is critical for seismic hazard assessment because their reactivation could result in destructive earthquakes.

There is growing interest in analyzing interdisciplinary datasets to better understand the evolution of ecosystems through deep time. One burgeoning area has been the integration of archaeological and fossil data to evaluate the long-term structure and function of habitats, floral and faunal communities, and ecosystems. Here, marine invertebrate data from Holocene archaeological sites and Pleistocene marine terrace deposits on California's Northern Channel Islands are combined to glean insights into the long-term structure of nearshore marine ecosystems, the composition of intertidal marine invertebrate communities, and the formation of archaeological shell middens. While a variety of methodological, analytical, and taphonomic challenges in comparing disparate datasets from fossil and archaeological contexts were identified, we offer perspectives for surmounting these challenges in future research. These findings indicate that the integration of fossil and archaeological data, spanning tens of thousands of years, offers important insights on the evolution of nearshore coastal ecosystems and marine climate change in California and around the world.

Today, glaciers in the western Altiplano are very scarce, even on peaks exceeding 6000 m. In this mostly ice-free landscape, however, moraines and other glacial deposits are commonly found attesting to quite different climate conditions that favored the advance of glaciers in the past. Although other areas of the Altiplano have been commonly accounted for regarding paleoclimate reconstructions, western Altiplano has been often overlooked. Here we present a detailed map of glacial landforms and a paleoglacier reconstruction from a test area in the western Altiplano between 18.5° and 19°S. We reconstructed regional equilibrium line altitudes (ELA) for several moraine stages, representing extensive past glacier advances in the region. During a prominent and ubiquitous ‘Principal Moraine (PM)’ stage glaciers from most peaks and all orientations advanced to altitudes of up to 4000 m asl. Reconstructed PM ELAs along 90 valleys range from 4400 to 5000 m asl. ELA distribution reveals a strong aspect-dependency at the western boundary of the Altiplano, with ELAs 300 m lower on west-facing glaciers than east-facing glaciers. The coincidence of such steep gradient with a prominent NW-SE ridge accounts for topographic control on the precipitation and thus in the advance of glaciers along the western boundary of the Altiplano. To the east, ELAs from the peaks towering the Altiplano are comparable to ELAs from east-facing glaciers at the western Altiplano boundary but show little to no aspect-dependency. Since these patterns cannot be solely explained by increased moisture advection from the Amazon basin, we suspect that western-sourced moisture associated with increased frequency of cold fronts and cut-off events played an important role in the glacier dynamics at this latitude. Nevertheless, further investigations are required to evaluate the relative role of both precipitation regimes on the glacier dynamics from the westernmost Altiplano.

Secondary weathering of exposed continental shelf sediment at low-latitudes may play a significant role in atmospheric CO₂ consumption during glacial periods, which is negative feedback for climate stability. However, more lines of evidences are required to verify the link of glacial weathering with climate. This study presents a comprehensive analysis of geochemical proxies that indicate the silicate weathering intensity in the northern South China Sea (SCS) over orbital timescales since ∼244 ka. Provenance discrimination results, based on the Sr-Nd isotopes values and the patterns of rare earth elements (REEs), suggest that the terrigenous sediment was primarily derived from Taiwan Island. The silicate weathering records revealed two different weathering regimes during glacial periods in the northern SCS, corresponding to changes in monsoon climate and sea-level. During the early period of Marine Isotope Stage 6 (MIS 6), the increase in weathering intensity was in response to climate variability, and the rapid delivery of terrigenous sediment through contour currents allowed for the preservation of climate signals in the continental margin. In contrast, the significant increase in weathering intensity during the glacial periods at late MIS 2 and late MIS 6, was a result of the sedimentary recycling process dominated by sea-level rises. In this case, the marginal sea weathering records did not truly reflect climate changes, due to secondary weathering processes on the exposed continental shelf. Our new geochemical results emphasize the dynamic coupling effects of climate and sea-level changes in transmitting and preserving silicate weathering signals at low-latitude during glacial periods. When using marginal sea sediments for paleoclimatic and paleo-weathering reconstruction, one should be cautious of the complex influence of sediment source-to-sink processes on sediment composition, and a holistic approach may provide more robust constraints.

The climate in the South Atlantic sector of the sub-Antarctic, and therefore on and around the island of South Georgia, is dependent on the Southern Hemisphere Westerlies (SHW) and the Antarctic Circumpolar Current (ACC). The SHW and the ACC, in turn, are strongly controlled by climate variability in the Southern Hemisphere. Accordingly, thick sediment sequences in the troughs across South Georgia's continental shelf serve as valuable archives for past climate variations in the Southern Ocean. Since Holocene climate fluctuations led to only minimal oscillations in glacier margin positions within the fjords, the entire shelf was exposed to dynamic ocean currents since at least 10 ka BP. Its depositional systems are therefore a suitable target for the reconstruction of Holocene dynamics of both the SHW and the ACC. Sub-bottom profiler data and radiocarbon ages from four gravity cores from the south-western South Georgia continental shelf provide evidence for a complex interplay between island run-off and ocean currents intruding into a unique cross-shelf trough system during the last ∼10 ka. The data reveal several prominent changes in sediment and Holocene climate dynamics, the most significant occurring between 8 and 7.7 cal ka BP and between 2.6 and 2.2 cal ka BP. Both of these time periods represent transitions from warmer to cooler and windier conditions in South Georgia and the Southern Hemisphere. Our record from the King Haakon Trough System is the first highly resolved Holocene archive from the marine realm on the south-western South Georgia continental shelf and suggests several large-scale Southern Hemisphere climate changes during the mid-to late Holocene.

This study has investigated the surge height along the Bangladesh coast due to the changes in future cyclone characteristics. Cyclone characteristics mainly translation speed, landfall angle, maximum sustained wind radius, genesis behavior etc., were investigated with the present and future cyclone data calibration. We have used the d4PDF, AGCM data, and BMD data for calibration. An equation for a vertical shallow water model was developed and used to determine the water level elevation resulting from the modified cyclone information. The cyclone modification information was made by the calibration of present and past cyclone data. It is found from the study that the west part of Bangladesh will face intense cyclones but the East part may face the dangerous cyclone in the future. We have also seen that changes in the characteristics of storms result in a major change of storm surge.

The relationship between historical climate change and past agricultural production contributes to a better understanding of the impacts of projected climate change by providing empirical data for resilient human responses. This study explores the periods of dynastic transitions and crop production at the urban site of Vadnagar, in semi-arid northwest India through several climate events, generally characterised by weakening summer monsoon precipitation during the Late Holocene. Artefacts from the site present an unbroken sequence of seven successive cultures from the first century BCE to the nineteenth century CE. Archaeobotanical data indicate the sufficient water availability during the Historic and Medieval periods, allowing crop production dominated large-grained cereals (C₃ plants). However, during the Post-Medieval period (ca.1300−1850 CE) a resilient crop economy based on small-grained cereals (C₄ plants) dominated, representing a human adaptation to prolonged weakening of monsoonal precipitation. Isotopic and phytolith data at the site present a clear signal of changing local environmental conditions over two millennia, consistent with regional palaeoclimate records, providing and interpretive context for agricultural evidence at Vadnagar. Despite long-term reduction in summer humidity, we argue that an adaptable agricultural package coupled with suitable water management systems allowed for the resilience of the urban settlement at Vadnagar.