The Pliocene-Pleistocene transition(3.0-2.5 million years ago,Ma)was a critical period during which the Arctic ice sheets expanded extensively and intensified,with the establishment of a permanent ice sheet on Greenla...The Pliocene-Pleistocene transition(3.0-2.5 million years ago,Ma)was a critical period during which the Arctic ice sheets expanded extensively and intensified,with the establishment of a permanent ice sheet on Greenland marking the onset of a bipolar“icehouse”climate state.This interval,characterized by atmospheric CO_(2) concentrations between pre-industrial and modern levels(~280-400 ppmv),provides a critical time window for understanding ice-sheet response to external forcing.Using a high-resolution climate model and a 3D thermomechanical ice sheet model,we simulate the Greenland Ice Sheet(GrIS)volume evolution under different CO_(2) scenarios and analyze its periodic behavior during this period.Our results show that when the GrIS volume was small,its variability was strongly paced by 65°N summer insolation.As the ice sheet grew,its response shifted,becoming increasingly dominated by the obliquity cycle.The GrIS volume reconstruction,consistent with ice-rafted debris records,indicates that after approximately 2.7 Ma,the expanded GrIS exhibited enhanced suborbital to millennial-scale signals and greater ice dynamical variability-a pattern echoing the amplified millennial-scale climate events observed in late Quaternary Greenland ice cores.Furthermore,comparison with deep-sea oxygen isotope records shows that the GrIS began to significantly contribute to the 40,000-year cycle after 2.7 Ma,with its changes slightly leading the signal of the benthic δ^(18)O.This study clarifies the GrIS’s cyclic evolution and constrains its role in the climate system evolution during the Pliocene-Pleistocene transition.展开更多
From the Siwalik Group of Haryana and Himachal Pradesh, new fossil reptile records are described. The Siwalik fauna from Haryana and Himachal is recorded from the pre-Pinjor and Pinjor beds (Upper Siwalik Subgroup: Pl...From the Siwalik Group of Haryana and Himachal Pradesh, new fossil reptile records are described. The Siwalik fauna from Haryana and Himachal is recorded from the pre-Pinjor and Pinjor beds (Upper Siwalik Subgroup: Pliocene—Lower Pleistocene). The reptile fauna includes Crocodylus aff. palustris, Gavialis cf. gangeticus, Rhamphosuchus crassidens, Batagur sp., Geoclemys hamiltoni and Hardella thurjii. The findings are significant as fossil reptiles from the Siwalik Group are scanty as compared to the richer mammalian fauna.展开更多
Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen isotope stratigraphy has been applied to the ...Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen isotope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Furthermore, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferal δ180 record shows that before ~3.1 Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1-2.5 Ma demonstrates the formation of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST) reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ18O, might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversible SST reductions during the period of ~2.2-0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.展开更多
基金funded by the Strategy Priority Research Program(Category B)of the Chinese Academy of Sciences(Grant No.XDB0710000)the National Key Research and Development Program(No.2022YFF0801504)+1 种基金the National Natural Science Foundation of China(Nos.42488201,41907371)support from the IGGCAS Key Program(No.IGGCAS-202201).
文摘The Pliocene-Pleistocene transition(3.0-2.5 million years ago,Ma)was a critical period during which the Arctic ice sheets expanded extensively and intensified,with the establishment of a permanent ice sheet on Greenland marking the onset of a bipolar“icehouse”climate state.This interval,characterized by atmospheric CO_(2) concentrations between pre-industrial and modern levels(~280-400 ppmv),provides a critical time window for understanding ice-sheet response to external forcing.Using a high-resolution climate model and a 3D thermomechanical ice sheet model,we simulate the Greenland Ice Sheet(GrIS)volume evolution under different CO_(2) scenarios and analyze its periodic behavior during this period.Our results show that when the GrIS volume was small,its variability was strongly paced by 65°N summer insolation.As the ice sheet grew,its response shifted,becoming increasingly dominated by the obliquity cycle.The GrIS volume reconstruction,consistent with ice-rafted debris records,indicates that after approximately 2.7 Ma,the expanded GrIS exhibited enhanced suborbital to millennial-scale signals and greater ice dynamical variability-a pattern echoing the amplified millennial-scale climate events observed in late Quaternary Greenland ice cores.Furthermore,comparison with deep-sea oxygen isotope records shows that the GrIS began to significantly contribute to the 40,000-year cycle after 2.7 Ma,with its changes slightly leading the signal of the benthic δ^(18)O.This study clarifies the GrIS’s cyclic evolution and constrains its role in the climate system evolution during the Pliocene-Pleistocene transition.
文摘From the Siwalik Group of Haryana and Himachal Pradesh, new fossil reptile records are described. The Siwalik fauna from Haryana and Himachal is recorded from the pre-Pinjor and Pinjor beds (Upper Siwalik Subgroup: Pliocene—Lower Pleistocene). The reptile fauna includes Crocodylus aff. palustris, Gavialis cf. gangeticus, Rhamphosuchus crassidens, Batagur sp., Geoclemys hamiltoni and Hardella thurjii. The findings are significant as fossil reptiles from the Siwalik Group are scanty as compared to the richer mammalian fauna.
基金the National Natural Science Foundation of China (Grant No. 49999560) and the State key Basic Research and Development Plan of China (Grant No. G2000078503).
文摘Based on the stable isotopic analysis of more than 1000 samples of planktonic and benthic foraminifers from ODP Site 1148 in the northern South China Sea (SCS), the oxygen isotope stratigraphy has been applied to the last 3 million years for the first time in the SCS. Furthermore, the paleoceanographic changes in the northern SCS during the last 6 million years have been unraveled. The benthic foraminiferal δ180 record shows that before ~3.1 Ma the SCS was much more influenced by the warm intermediate water of the Pacific. The remarkable decrease in the deepwater temperature of the SCS during the period of 3.1-2.5 Ma demonstrates the formation of the Northern Hemisphere ice-sheet. However, the several sea surface temperature (SST) reductions during the early and middle Pliocene, reflected by the planktonic foraminiferal δ18O, might be related to the ice-sheet growth in the Antarctic region. Only those stepwise and irreversible SST reductions during the period of ~2.2-0.9 Ma could be related to the formation and growth of the Northern Hemisphere ice-sheet.
