The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from t...The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change.Here,we report sedimentologic,geochronologic,and provenance data from a drill core near the Sanmen Gorge,the last gorge along the main course of the Yellow River.Our results indicate that typical river channel deposits,with detritus from the Ordos Block in the upstream regions,started to accumulate in the Sanmen Gorge at~1.25 Ma.When integrated with river terrace evidence from the upstream and downstream regions,the results provide robust evidence that the final integration of the modern Yellow River occurred at~1.25 Ma,consistent with the beginning of the Mid-Pleistocene transition(MPT).We propose that the accelerated lowering of eustatic sea level during the MPT may play as important a role as tectonism in driving the birth and evolution of the modern Yellow River.展开更多
European mountain systems have played a crucial role in shaping the distribution of species and of their genetic diversity during the Quaternary climatic changes,with the establishment of allopatric patterns across ma...European mountain systems have played a crucial role in shaping the distribution of species and of their genetic diversity during the Quaternary climatic changes,with the establishment of allopatric patterns across main mountain ranges.Here we investigated the evolutionary history of fea beetles of the Longitarsus candidulus species-group showing an uncommon disjunct biogeographic pattern across the Apennine and the Pyrenees.We applied a multilocus molecular approach and multispecies coalescent models to establish a phylogenetic and systematic framework for this morphologically homogeneous species-group and to estimate the time of main cladogenetic events underlying the origin of the Apennine-Pyrenees pattern.We found strong support for the monophyly of the candidulus group with a sister relationship between Longitarsus laureolae and L.leonardii endemic to the Apennine and the Pyrenees mountains respectively.The timing of speciation events in the candidulus species-group coincides with 2 major climatic transitions during the Early and Middle Pleistocene which resulted in signifcant environmental changes in Europe and suggest a scenario of allopatric isolation and divergence on distinct mountain ranges.The split between the thermophilic species L.candidulus and the ancestor of the temperate species L.laureolae and L.leonardii is estimated at~3 Ma during the transition from Pliocene to Pleistocene and was probably triggered by their segregation in xerophilous and temperate habitats.The speciation between L.laureolae and L.leonardii,estimated at~1 Ma during the Mid-Pleistocene Transition,can be explained by the establishment of unfavorable conditions in West Alps and Central Massif underlying the onset of the Apennine-Pyrenees disjunct pattern.Finally,the strict association between members of the candidulus group and distinct Thymelaeaceae plants suggests further studies to address the hypothesis that speciation in these fea beetles might have been also associated with Pleistocene range changes of their host plants.展开更多
Milankovitch Theory shows that glacial-interglacial cycles in the Quaternary are related to the variation of solar insolation forcing linked to the earth＇s astronomical parameters.However,the summer insolation at nor...Milankovitch Theory shows that glacial-interglacial cycles in the Quaternary are related to the variation of solar insolation forcing linked to the earth＇s astronomical parameters.However,the summer insolation at northern high latitudes,usually considered as the main external forcing for the ice age as Milankovitch pointed out,is marked by the 19- and 23-ka precession periodicities,which is not consistent with the glacial-interglacial cycles.On the other hand,recent studies indicate that the annual mean insolation dominated by the obliquity is also an important external forcing in glacial cycles.In this paper,it is assumed that the glacial oscillation is regulated simultaneously by the annual mean insolation at northern high latitudes related to obliquity and the noon insolation at summer solstice at the ice-line latitude related to precession. Only when both of them exceed some thresholds,does the ice sheet start to melt continuously to induce the global warming and deglaciation.Furthermore,the periodicity transition of glacial cycles at mid-Pleistocene was a natural change when the ice sheet thickness altered.A conceptual model based on this idea gives encouraging results compared with the isotopic data.展开更多
The mid-Pleistocene climate transition （MPT） has been widely reported in worldwide geological events. As a key issue of the Quaternary geology, it has attracted much attention from the paleoclimate community. MPT re...The mid-Pleistocene climate transition （MPT） has been widely reported in worldwide geological events. As a key issue of the Quaternary geology, it has attracted much attention from the paleoclimate community. MPT refers to a period lasting for several hundreds of thousand years, during which the dominant climate periodicity gradually extended from 41 kyr to 100 kyr （Ruddiman et al., 1989）,展开更多
Ice cores have revolutionized our views of the Earth system.They record past climatic and environmental parameters that range on time scales from synoptic events to hundreds of thousands of years.For instance,the Vost...Ice cores have revolutionized our views of the Earth system.They record past climatic and environmental parameters that range on time scales from synoptic events to hundreds of thousands of years.For instance,the Vostok ice core reached an age of 420 ka(thousand years)(Figure 1),revealing a close linkage between climate and greenhouse gas concentrations over the last four glacial-interglacial cycles(Petit et al.,1999).展开更多
基金supported by the Fundamental Research Funds for the Central Universities,China(lzujbky-2021-ey12)the National Natural Science Foundation of China(42072211)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0602)the National Non-Profit Fundamental Research Grant of China(IGCEA 2008)。
文摘The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change.Here,we report sedimentologic,geochronologic,and provenance data from a drill core near the Sanmen Gorge,the last gorge along the main course of the Yellow River.Our results indicate that typical river channel deposits,with detritus from the Ordos Block in the upstream regions,started to accumulate in the Sanmen Gorge at~1.25 Ma.When integrated with river terrace evidence from the upstream and downstream regions,the results provide robust evidence that the final integration of the modern Yellow River occurred at~1.25 Ma,consistent with the beginning of the Mid-Pleistocene transition(MPT).We propose that the accelerated lowering of eustatic sea level during the MPT may play as important a role as tectonism in driving the birth and evolution of the modern Yellow River.
文摘European mountain systems have played a crucial role in shaping the distribution of species and of their genetic diversity during the Quaternary climatic changes,with the establishment of allopatric patterns across main mountain ranges.Here we investigated the evolutionary history of fea beetles of the Longitarsus candidulus species-group showing an uncommon disjunct biogeographic pattern across the Apennine and the Pyrenees.We applied a multilocus molecular approach and multispecies coalescent models to establish a phylogenetic and systematic framework for this morphologically homogeneous species-group and to estimate the time of main cladogenetic events underlying the origin of the Apennine-Pyrenees pattern.We found strong support for the monophyly of the candidulus group with a sister relationship between Longitarsus laureolae and L.leonardii endemic to the Apennine and the Pyrenees mountains respectively.The timing of speciation events in the candidulus species-group coincides with 2 major climatic transitions during the Early and Middle Pleistocene which resulted in signifcant environmental changes in Europe and suggest a scenario of allopatric isolation and divergence on distinct mountain ranges.The split between the thermophilic species L.candidulus and the ancestor of the temperate species L.laureolae and L.leonardii is estimated at~3 Ma during the transition from Pliocene to Pleistocene and was probably triggered by their segregation in xerophilous and temperate habitats.The speciation between L.laureolae and L.leonardii,estimated at~1 Ma during the Mid-Pleistocene Transition,can be explained by the establishment of unfavorable conditions in West Alps and Central Massif underlying the onset of the Apennine-Pyrenees disjunct pattern.Finally,the strict association between members of the candidulus group and distinct Thymelaeaceae plants suggests further studies to address the hypothesis that speciation in these fea beetles might have been also associated with Pleistocene range changes of their host plants.
基金Supported by the National Natural Science Foundation of China under Grant Nos.40875043 and 40631002the National Program on Key Basic Research of China(2010CB428506)
文摘Milankovitch Theory shows that glacial-interglacial cycles in the Quaternary are related to the variation of solar insolation forcing linked to the earth＇s astronomical parameters.However,the summer insolation at northern high latitudes,usually considered as the main external forcing for the ice age as Milankovitch pointed out,is marked by the 19- and 23-ka precession periodicities,which is not consistent with the glacial-interglacial cycles.On the other hand,recent studies indicate that the annual mean insolation dominated by the obliquity is also an important external forcing in glacial cycles.In this paper,it is assumed that the glacial oscillation is regulated simultaneously by the annual mean insolation at northern high latitudes related to obliquity and the noon insolation at summer solstice at the ice-line latitude related to precession. Only when both of them exceed some thresholds,does the ice sheet start to melt continuously to induce the global warming and deglaciation.Furthermore,the periodicity transition of glacial cycles at mid-Pleistocene was a natural change when the ice sheet thickness altered.A conceptual model based on this idea gives encouraging results compared with the isotopic data.
基金financially supported by the Geological Investigation Project of China Geological Survey(No.12120113006200)
文摘The mid-Pleistocene climate transition （MPT） has been widely reported in worldwide geological events. As a key issue of the Quaternary geology, it has attracted much attention from the paleoclimate community. MPT refers to a period lasting for several hundreds of thousand years, during which the dominant climate periodicity gradually extended from 41 kyr to 100 kyr （Ruddiman et al., 1989）,
基金supported by the Natural Science Foundation of China(Grant nos.41830644,42021001).
文摘Ice cores have revolutionized our views of the Earth system.They record past climatic and environmental parameters that range on time scales from synoptic events to hundreds of thousands of years.For instance,the Vostok ice core reached an age of 420 ka(thousand years)(Figure 1),revealing a close linkage between climate and greenhouse gas concentrations over the last four glacial-interglacial cycles(Petit et al.,1999).
