The Last Glacial Maximum (LGM, c. 26-16 ka) and the Holocene Optimum (HO, c. 9-5 ka) were characterized by cold-dry and warm-wet climates respectively in the recently geological Earth. How Chinese deserts and sand fie...The Last Glacial Maximum (LGM, c. 26-16 ka) and the Holocene Optimum (HO, c. 9-5 ka) were characterized by cold-dry and warm-wet climates respectively in the recently geological Earth. How Chinese deserts and sand fields responded to these distinctive climatic changes is still not clear, however. To reconstruct environments of the deserts and sand fields during the LGM and HO is helpful to understand the forcing mechanisms of environment change in this arid region, and to test paleoclimatic modeling results. Through our long-term field and laboratory investigations, 400 optically stimulated luminescence (OSL) ages and more than 100 depositional records in the Chinese deserts and sand fields were obtained; on the basis of these data, we reconstruct spatial distributions of the deserts and sand fields during the LGM and HO. Our results show that the sand fields of Mu Us, Hunshandake, Horqin and Hulun Buir in northern and northeastern China had expanded 25%, 37%, 38% and 270%, respectively, during the LGM; the sand fields of Gonghe in the northeastern Qinghai-Tibetan Plateau had expanded 20%, and the deserts of Badain Jaran, Tengger in central northern China had expanded 39% and 29% separately during the LGM; the deserts of Taklimakan, Gurbantünggüt and Kumtag in northwestern China had expanded 10%-20% respectively, compared to their modern areas. On the other hand, all of the sand fields were nearly completely covered by vegetation during the HO; the deserts in northwestern and central northern China were reduced by around 5%-20% in area during this time. Lakes in this arid region were probably expanded during the HO but this conclusion needs more investigation. Compared with the geological distributions of deserts and sand fields, human activity has clearly changed (expanded) the area of active sand dunes at the present time. Our observations show that environmental conditions of Chinese deserts and sand fields are controlled by regional climate together with human activity.展开更多
The dune system in Otindag sand field of northern China is sensitive to climate change, where effective moisture and related vegetation cover play a controlling role for dune activity and stability. Therefore, aeolian...The dune system in Otindag sand field of northern China is sensitive to climate change, where effective moisture and related vegetation cover play a controlling role for dune activity and stability. Therefore, aeolian deposits may be an archive of past environmental changes, possibly at the millennial scale, but previous studies on this topic have rarely been reported. In this study, thirty-five optically stimulated luminescence (OSL) ages of ten representative sand-paleosol profiles in Otindag sand field are ob-tained, and these ages provide a relatively complete and well-dated chronology for wet and dry varia-tions in Holocene. The results indicate that widespread dune mobilization occurred from 9.9 to 8.2 ka, suggesting a dry early Holocene climate. The dunes were mainly stabilized between 8.0 and 2.7 ka, implying a relatively wet climate, although there were short-term penetrations of dune activity during this wet period. After ~2.3 ka, the region became dry again, as inferred from widespread dune activity. The '8.2 ka' cold event and the Little Ice Age climatic deterioration are detected on the basis of the dune records and OSL ages. During the Medieval Warm Period and the Sui-Tang Warm Period (570-770 AD), climate in Otindag sand field was relatively humid and the vegetation was denser, and the sand dunes were stabilized again. These aeolian records may indicate climate changes at millennial time scale during Holocene, and these climatic changes may be the teleconnection to the climate changes elsewhere in the world.展开更多
Chinese loess deposits are some of the best continental records of palaeoclimatic and pa- laeoenvironmental changes in the late Cenozoic. Many investigations have shown that the long-time climate variations recorded b...Chinese loess deposits are some of the best continental records of palaeoclimatic and pa- laeoenvironmental changes in the late Cenozoic. Many investigations have shown that the long-time climate variations recorded by the loess-paleosol sequences can be correlated with global environ- mental changes. However,there are still some foundational questions concerning loess deposition that are not well answered,casting uncertainty on many previous conclusions,especially high-resolu- tion palaeoclimatic records. In this study,three typical loess-paleosol sections spanning the last glacial cy- cle were closely sampled for optically stimulated lu- minescence (OSL) dating and palaeoclimate inter- pretation along a northwest-southeast transect in Chinese Loess Plateau. Results show that there is a 4-5 ka hiatus in the typical loess deposits,and as a consequence suggests that the loess record is not continuous over millennial time scales. As such,pre- vious conclusions on climatic and environmental changes at millennial-centennial time scale,recon- structed through the loess record,should be reinves- tigated. The erosional hiatus may be forced by a pe- riod with strengthened East Asian winter monsoon and the less vegetation cover in the investigated sites.展开更多
基金supported by the Global Changes Program of Ministry of Science and Technology of China(2010CB950203)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA05120704)+1 种基金the National Natural Science Foundation of China(40930103 and 41021002)China National Science and Technology Basic Work Program(2006FY110800 and 2012FY111700)
文摘The Last Glacial Maximum (LGM, c. 26-16 ka) and the Holocene Optimum (HO, c. 9-5 ka) were characterized by cold-dry and warm-wet climates respectively in the recently geological Earth. How Chinese deserts and sand fields responded to these distinctive climatic changes is still not clear, however. To reconstruct environments of the deserts and sand fields during the LGM and HO is helpful to understand the forcing mechanisms of environment change in this arid region, and to test paleoclimatic modeling results. Through our long-term field and laboratory investigations, 400 optically stimulated luminescence (OSL) ages and more than 100 depositional records in the Chinese deserts and sand fields were obtained; on the basis of these data, we reconstruct spatial distributions of the deserts and sand fields during the LGM and HO. Our results show that the sand fields of Mu Us, Hunshandake, Horqin and Hulun Buir in northern and northeastern China had expanded 25%, 37%, 38% and 270%, respectively, during the LGM; the sand fields of Gonghe in the northeastern Qinghai-Tibetan Plateau had expanded 20%, and the deserts of Badain Jaran, Tengger in central northern China had expanded 39% and 29% separately during the LGM; the deserts of Taklimakan, Gurbantünggüt and Kumtag in northwestern China had expanded 10%-20% respectively, compared to their modern areas. On the other hand, all of the sand fields were nearly completely covered by vegetation during the HO; the deserts in northwestern and central northern China were reduced by around 5%-20% in area during this time. Lakes in this arid region were probably expanded during the HO but this conclusion needs more investigation. Compared with the geological distributions of deserts and sand fields, human activity has clearly changed (expanded) the area of active sand dunes at the present time. Our observations show that environmental conditions of Chinese deserts and sand fields are controlled by regional climate together with human activity.
基金the Basic Research Project of China (Grant No.2004CB720201)US National Science Foundation (Grant Nos.ATM-0502489 and ATM-0502511)the Open Fund of State Key Laboratory of Loess and Quaternary Geology (Grant No. 0711)
文摘The dune system in Otindag sand field of northern China is sensitive to climate change, where effective moisture and related vegetation cover play a controlling role for dune activity and stability. Therefore, aeolian deposits may be an archive of past environmental changes, possibly at the millennial scale, but previous studies on this topic have rarely been reported. In this study, thirty-five optically stimulated luminescence (OSL) ages of ten representative sand-paleosol profiles in Otindag sand field are ob-tained, and these ages provide a relatively complete and well-dated chronology for wet and dry varia-tions in Holocene. The results indicate that widespread dune mobilization occurred from 9.9 to 8.2 ka, suggesting a dry early Holocene climate. The dunes were mainly stabilized between 8.0 and 2.7 ka, implying a relatively wet climate, although there were short-term penetrations of dune activity during this wet period. After ~2.3 ka, the region became dry again, as inferred from widespread dune activity. The '8.2 ka' cold event and the Little Ice Age climatic deterioration are detected on the basis of the dune records and OSL ages. During the Medieval Warm Period and the Sui-Tang Warm Period (570-770 AD), climate in Otindag sand field was relatively humid and the vegetation was denser, and the sand dunes were stabilized again. These aeolian records may indicate climate changes at millennial time scale during Holocene, and these climatic changes may be the teleconnection to the climate changes elsewhere in the world.
基金the National Natural Science Foundation of China （Grant Nos.40325007, 40121303） NBRPC （Grant No.2004CB720506） and the Royal Society.
文摘Chinese loess deposits are some of the best continental records of palaeoclimatic and pa- laeoenvironmental changes in the late Cenozoic. Many investigations have shown that the long-time climate variations recorded by the loess-paleosol sequences can be correlated with global environ- mental changes. However,there are still some foundational questions concerning loess deposition that are not well answered,casting uncertainty on many previous conclusions,especially high-resolu- tion palaeoclimatic records. In this study,three typical loess-paleosol sections spanning the last glacial cy- cle were closely sampled for optically stimulated lu- minescence (OSL) dating and palaeoclimate inter- pretation along a northwest-southeast transect in Chinese Loess Plateau. Results show that there is a 4-5 ka hiatus in the typical loess deposits,and as a consequence suggests that the loess record is not continuous over millennial time scales. As such,pre- vious conclusions on climatic and environmental changes at millennial-centennial time scale,recon- structed through the loess record,should be reinves- tigated. The erosional hiatus may be forced by a pe- riod with strengthened East Asian winter monsoon and the less vegetation cover in the investigated sites.
