Search

The Luo River is located in the southern part of the Chinese Loess Plateau and the northern part of the Weihe Basin, in Central China. In the basin it flows proximal to the site of the Luyang Wetland core, which is an important archive of climate change over the past 1 Myr in this region. In this paper, the contribution of the Luo River to the sedimentary record is analyzed by reconstructing the evolution of this river during the Middle to Late Pleistocene. It is argued that an alluvial fan of the Luo River has contributed to the sedimentary archive until approximately 200–240 ka. From this moment onwards, the fan became incised and terraces began to form. The formation of a new alluvial fan further downstream led to the disconnection of the Luo River from the Luyang Wetland core site. We propose that this series of events was caused by the displacement of an intra-basinal fault and the resultant faulting-forced folding, which caused increased relative subsidence, and thus increased sedimentation rates at the core site. Therefore, a complete sediment record in the ‘Luyang Wetland’ was preserved, despite the disconnection from the Luo River. The chronology of the fans and terraces was established using existing age control (U-series, ESR, OSL, pIRIR 290 and magnetic susceptibility correlation), and through correlation of the loess-paleosol cover to marine isotope stages. Based on sedimentological characteristics of the fluvial sequence, we suggest that incision of the Luo River occurred in two steps. Small incisions took place at transitions to interglacials and the main incision phases occur at the transition from an interglacial to glacial climate. Due to the incision, basal parts of the oldest Luo River alluvial fan are exposed, and it is in one of these exposures that the famous Dali Man skull was retrieved. This study shows that the Dali Man did not live on a river terrace as previously thought, but on an aggrading alluvial fan, during wet, glacial conditions. [ABSTRACT FROM AUTHOR]

Based on the data of five observed meteorological elements (temperature, precipitation, wind speed, sunshine duration, and relative humidity) from 22 stations, the paper investigated the climate variations in northern Xinjiang over the past 50 years. The analytical results showed that both the temperature and the precipitation have increased significantly (0.35 °C/10 y, 11.2 mm/10 y) during the period of 1960–2011. An abrupt change was detected to have occurred in 1986 for temperature and in 1987 for precipitation. Autumn was the season when the temperature increased most dramatically, and winter and autumn were the seasons when the precipitation increased most dramatically. The twenty years after 1990 were the warmest and wettest two decades of the past ∼50 years, but the warming and wetting paces have slowed down during the same period. The results also showed that the mean annual minimum temperature increased more dramatically than the mean annual maximum temperature, resulting in a greatly reduced diurnal range. The reasons or mechanisms for rising trend of temperature during the past 50 years and also for the faster rising rate of the temperature in northern Xinjiang and the adjacent areas have been reasonably explored in published literature. However, the reasons or mechanisms for the rising trend of the past 50-year precipitation in northern Xinjiang and the adjacent areas have not been reasonably explored. This wetting trend has not extended further to the surrounding areas including Republic of Mongolia, major part of North China, and five republics of the former Soviet Union, and the need is thus pressing to explore the reasons or mechanisms behind this relatively “localized” wetting trend. [ABSTRACT FROM AUTHOR]

Abstract: As a paradigm of greenhouse climate in Earth's history, the Cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate. The Songliao Basin, among the longest duration (85–90m.y.) of continental sedimentary basins, provides an excellent opportunity to recover a nearly complete Cretaceous terrestrial sedimentary record. Extensive lake deposits, ten-kilometers deep and covering an area of 260,000km2 of the Songliao Basin, provide unique, detailed records that can be tied to the global stratigraphic time scale, thereby improving our understanding of the continental paleoclimate and ecological system. The two coreholes at SKIs and SKIn sites were drilled into this basin and completed with a total length of 2485.89m of recovered core that spanned the complete middle-to-Upper Cretaceous strata in the basin. The unique geological setting of long-term continuous subsidence within the largest Cretaceous landmass in the world — makes the Cretaceous Songliao Basin of northeastern China an ideal place to study Cretaceous climate change on the continent. This paper reviews the literature on the paleogeography and paleoclimate of the northern East Asia and the Songliao Basin during the Cretaceous. Based on the climatologically sensitive deposits, oxygen isotope studies, and paleontology, the climate during the Cretaceous in the Songliao Basin was temperate and humid with relatively abundant rainfall. During the period, significant changes – four cooling, three warming, and three semiarid events – are generally consistent with the oxygen isotope data from East Asia, and the four cooling events, in Berriasian–Valanginian, Aptian–Albian, early Santonian, and Campanian–Maastrichtian, may be related to potential glaciations in Cretaceous. [Copyright &y& Elsevier]

Abstract: The Continental Scientific Drilling Project at the Cretaceous-age Songliao Basin is a drilling initiative under the framework of the International Continental Scientific Drilling Program, to recover a nearly complete Cretaceous terrestrial sedimentary record in the Songliao Basin, northeastern China. The recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the Cretaceous greenhouse world, and provide a documentation of geological events relevant to the carbon cycle during this time period. This drilling project will address significant geological questions, such as the identification of important stratigraphic boundaries and the marine-terrestrial correlations of stratigraphy, the reasons for the biotic response to the terrestrial environmental changes, the terrestrial response to the Cretaceous oceanic anoxic events, the formation of terrestrial petroleum source rocks, and the mechanisms for the Cretaceous magnetic Normal Superchron (CNS). In the first stage of this drilling project, the SKI drilling, rock cores of 2485.89m in total length were recovered and the recovery ratio reached 96.46%. A series of drilling and coring technologies including regular, confined, directional, and sealed coring, were utilized to ensure a higher recovery ratio for the core, and will be described at the end of this paper. Well loggings were conducted right after coring. Core handling and storage were arranged in such a way that the scientific research was conducted on half of each core, whereas the other half of each core was preserved for long-term storage. The upcoming second stage, the SKII drilling, will combine with data from the existing SKI to provide complete high-resolution climate records of the terrestrial environment for the whole Cretaceous time period. [Copyright &y& Elsevier]

Abstract: The Miocene vegetation and climate history of western China remains unclear. However, widely-distributed Miocene sediments of the Tianshui Basin in the NE Tibetan Plateau provide a great potential for deciphering the Miocene vegetation and climate history of this region. This paper presents first sporopollen record from these sediments, covering the period from 17.1 to 6.1Ma. Sporopollen data reveal that temperate, warm-temperate broad-leaved forest of Quercus, Ulmus and Betula dominated the Tianshui region between 17.1 and 14.7Ma, which was replaced by forest or forest-steppe of Ulmus, Artemisia and Betula between 14.7 and 11.7Ma. After a return to a broad-leaved forest of Betula and Quercus during 11.7–8.5Ma, the forest decreased rapidly and was replaced mostly by steppe vegetation (mainly composed of Artemisia, Chenopodiaceae and Poaceae) after 8.5Ma. We interpret the observed vegetation changes as a result of global climate change, which is characterized by global cooling, development of Arctic ice-sheets and permanent El Niño state after the Middle Miocene Climatic Optimum. The rapid development of steppe at about 8.5Ma suggested a permanent drying of the Asian interior at this time, coinciding with the onset of the well-known Hipparion red clay deposition in North China. [Copyright &y& Elsevier]

Abstract: This paper examines the spatial variation of sediment yield in the Yangtze basin in China, a large basin with complex geology, climate, land-use history, and extensive sediment monitoring. 287 stations with drainage area less than 10,000km2 were used to study the scale effects of sediment yield. In order to develop scale relations for regional sediment yield, the whole study area was divided into eight sub-basins. Relation between specific sediment yield and drainage basin area was built for each sub-basin. Regional scaling relation was analyzed based on landforms, geology, lithology and land-use of each sub-basin. Three regional trends were identified in relation to the drainage area: (1) a declining trend, due to soil erosion on heavily cultivated steep land and the storage of sediment in floodplains; (2) a flat trend, due to mass movement on the upper reach and heavy agricultural disturbance on the middle and lower reaches; and (3) an increasing trend, due to downstream recruitment of sediment from land downstream where slope farming and deforestation occurred. Using these developed relations, areally adjusted sediment yield maps were created over the entire Yangtze basin. [Copyright &y& Elsevier]

Abstract: Three Paleogene syn-rift intervals from the Bohai Bay Basin, the most petroliferous basin in China, were analyzed with sedimentological and geochemical techniques to characterize the lateral source rock heterogeneities, to reveal the environmental and ecological changes through geologic time and to construct depositional models for lacustrine source rocks under different tectonic and climatic conditions. The third (Es3) and first (Es1) members of the Eocene Shahejie Formation and the Oligocene Dongying Formation (Ed) display widely variable total organic carbon contents, hydrogen indices and visual kerogen compositions, suggesting changes in organic facies from deep to marginal sediments. Carefully selected deep-lake facies samples from any interval, however, display fairly uniform biomarker composition. These three intervals have distinctly different biomarker assemblages, which indicate weakly alkaline, freshwater lakes with a moderately deep thermocline during Es3 deposition, alkaline-saline lakes with shallow chemocline during Es1 deposition and acidic, freshwater lakes with deep, unstable thermocline during the deposition of the Dongying Formation. Such environmental changes corresponded to changes in subsidence rate and paleoclimate, from rapid subsidence and wet climate during Es3 deposition, through slow subsidence and arid climate during Es1 deposition to rapid subsidence and wet climate during Ed deposition and resulted in synchronous changes in terrigenous organic matter input, phytoplankton community and primary productivity. The co-evolution of environments and organisms controlled by tectonic subsidence and climate accounted for the deposition and distribution of high quality lacustrine source rocks with distinctly different geochemical characteristics. Most rift basins experienced changes in subsidence rates and possibly changes in climates during their syn-rift evolutions. The models constructed in this paper may have important implications for source rock prediction in other lacustrine rift basins. [Copyright &y& Elsevier]

Abstract: There is a wide distribution of thick evaporites in the He21 and He1 Members of the Wuyang Sag, Southern North China Basin. Based on drilling data, previous researchers have analyzed the formation mechanism of evaporites in Wuyang Sag, and considered that their origination stems from the insufficient provenance and dry climate of the area. However, other researchers have suggested that the Qinling-Dabie Mountains, on the southern part of Wuyang Sag, acted as a stable source material throughout the deposition period of the sag. These contrasting hypotheses indicate that further investigation is needed to clearly identify the evaporite genesis mechanism in Wuyang Sag. Using both seismic and geologic data, this paper analyzes the impact of the uplift structure of the Wuyan Sag area on evaporite formation. This analysis is based on restoration of the southern boundary of the sag in the deposition period with respect to the largest strike-slip fault. Taking the erosion of the lower Tertiary strata at the southern boundary of the sag (greatest tectonic activity) as the starting point of this study, and the movement of the NW strike-slip fault at the eastern part of the sag, the following conclusions were drawn: (1) The end stage of deposition of the He22 Member of the Hetaoyuan Formation was an important period in the base level transition for the Wuyang Sag. During the depositional period from the He3 Member to the He22 Member, the sag gradually expanded as the base level was rising. In the depositional period from the He21 Member to the He1 Member, the sag gradually shrank, and the base level was lowered due to the influence of structural uplift. In the meantime, inside the sag, the left-lateral strike-slip fault at the basement became active again and caused the eastern area of the strike-slip fault to be uplifted in the depositional period from the He21 Member to deposition of the Liaozhuang Formation. (2) The structure uplift during the depositional period from the He3 Member to the He22 Member blocked part of the provenance to infill the Wuyang Sag. Therefore, this activity resulted the sag becoming closed or semi-closed, leading to the deposition of evaporites. [Copyright &y& Elsevier]

Abstract: In this paper, we report 3780-m-thick Neogene deposits accumulated in the Kuqa foreland basin of southern Tianshan range, providing great potential for studying both tectonics and paleoclimatic changes. Based on palynological evidence, we discuss the paleoenvironmental changes as well as the interplay between regional uplift and climatic change in the region studied. Our results indicate that the vegetation and climatic changes from 13.3 to 7Ma were response to global climatic changes. After 7Ma, the uplift of the southern Tianshan range partially affects vegetation and climatic changes. Both global cooling and the rainshadow effect of uplifted high mountains affect the enhanced arid climate initiated ca. 5.23Ma ago. Such climatic changes are important archives in reconstructing paleoclimate of the Asian interior. [ABSTRACT FROM AUTHOR]