The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in thi...The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.展开更多
The tectonic cycle of the marginal sea basins in South China Sea(SCS)includes two cycles,i.e.,the formation and contraction of Palaeo-SCS and Neo-SCS.The northern part of SCS is a rift basin on a passive continental m...The tectonic cycle of the marginal sea basins in South China Sea(SCS)includes two cycles,i.e.,the formation and contraction of Palaeo-SCS and Neo-SCS.The northern part of SCS is a rift basin on a passive continental margin,while the the Nansha Block is a drifting rift basin.The southern part is a compound compressional basin on an active continental margin;the western part is a shear-extensional basin on a transform continental margin;the eastern part is an accretionary wedge basin on a subduction continental margin.The deep-water basins are mainly distributed on the continental slope and the the Nansha Block.There are three sets of source rocks in the deep-water areas of the northern continental margin in SCS,i.e.,Eocene terrestrial facies,early Oligocene transitional facies and late Oligocene marine facies.A set of Late Cretaceous-Early Oligocene terrestrial marine facies source rocks are developed in the drift-rift basin of SCS.Three sets of Oligocene,early Miocene and Mid-Miocene marine-terrestrial transitional facies source rocks are developed in the deep-water areas of both the southern and western continental margins of SCS.Four sets of reservoirs developed in the northern deep waters of SCS are dominated by deep sea fans.Two sets of reservoirs developed in the the Nansha Block are dominated by delta and biogenic reef.The southern part of SCS is dominated by deep sea fan and biogenic reef.Reservoirs of large channels and other clastic facies were developed in front of the estuaries,while biogenic reef bank was formed in the uplift zone.The hydrocarbon accumulation assemblages are mainly presented as Oligocene-Pliocene in the deep waters on the northern continental margin of SCS,Eocene-Lower Oligocene in the the Nansha Block,Oligocene-Pliocene and Oligocene-Miocene in the deep waters on the southern and western continental margin of SCS,respectively.The major hydrocarbon reservoir types in the deep waters of SCS are related to structural traps,deep water fans and biogenic reefs.The formation of basin,hydroc展开更多
文摘The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.
文摘The tectonic cycle of the marginal sea basins in South China Sea(SCS)includes two cycles,i.e.,the formation and contraction of Palaeo-SCS and Neo-SCS.The northern part of SCS is a rift basin on a passive continental margin,while the the Nansha Block is a drifting rift basin.The southern part is a compound compressional basin on an active continental margin;the western part is a shear-extensional basin on a transform continental margin;the eastern part is an accretionary wedge basin on a subduction continental margin.The deep-water basins are mainly distributed on the continental slope and the the Nansha Block.There are three sets of source rocks in the deep-water areas of the northern continental margin in SCS,i.e.,Eocene terrestrial facies,early Oligocene transitional facies and late Oligocene marine facies.A set of Late Cretaceous-Early Oligocene terrestrial marine facies source rocks are developed in the drift-rift basin of SCS.Three sets of Oligocene,early Miocene and Mid-Miocene marine-terrestrial transitional facies source rocks are developed in the deep-water areas of both the southern and western continental margins of SCS.Four sets of reservoirs developed in the northern deep waters of SCS are dominated by deep sea fans.Two sets of reservoirs developed in the the Nansha Block are dominated by delta and biogenic reef.The southern part of SCS is dominated by deep sea fan and biogenic reef.Reservoirs of large channels and other clastic facies were developed in front of the estuaries,while biogenic reef bank was formed in the uplift zone.The hydrocarbon accumulation assemblages are mainly presented as Oligocene-Pliocene in the deep waters on the northern continental margin of SCS,Eocene-Lower Oligocene in the the Nansha Block,Oligocene-Pliocene and Oligocene-Miocene in the deep waters on the southern and western continental margin of SCS,respectively.The major hydrocarbon reservoir types in the deep waters of SCS are related to structural traps,deep water fans and biogenic reefs.The formation of basin,hydroc
