Paleoenvironmental changes recorded by grain size of loess/paleosol sequence from the Chifeng City,Northeastern China since the Last Glacial

The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local environment.In this study,grain size end-member analysis of the Dajiugang(DJG)section deposited since the Last Glacial in Chifeng City,NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China.Results showed that the Chifeng loess comprises three grain size end-members(EM),EM1(7.38μm),EM2(49.4μm)and EM3(90.00μm),indicating the three transport dynamics of dust delivered to the region.The EM1 represents atmospheric dust as the background.The EM2,mainly derived from relatively distant-sources deposition,and EM3,material transported over a short distance,correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon(EAWM),respectively.Results of climate reconstruction,combined with other records,showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon(EASM)during the stadial-period[Marine Isotope Stage(MIS)4 and MIS 2 stage].The climate was predominantly warm and humid,with weak EAWM and surface winds and strong EASM in interstadial-period(MIS 3 and MIS 1 stage).Comparisons between indicators,e.g.,EM3,the LR04 benthicδ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.

Development of Sedimentary Environment in the Northeastern South China Sea Since the Last Glacial Stage

Core D （21°23′02″N, 116°47′13″E, water depth 405 m） was sampled from the upper slope from the northeastern South China Sea （SCS） and applied to analyze the sedimentary environmental change in this sea area since the last glacial stage. The results of grain size analysis, diatom analysis and detrital mineral analysis were well matched. We divided the core D into two layers. The surface sand layer （0 - 2 cm） consisted of residual sediments, which might be originally the sediment in the late Pleistocene and later suffered from being transformed in the post glacial transgression. The lower layer （2 - 130 cm） was quite different from the surface one, which might mainly result from a neritic sedimentary environment in the last glacial stage. Two sedimentary cycles could be detected in the core D： regression during Marine isotope stage （MIS） 4 to transgression during MIS 3 and regression during MIS 2 to transgression during the post glacial.

Characteristics and runoff volume of the Yangtze River paleo-valley at Nanjing reach in the Last Glacial Maximum

The stratigraphical cross-sections of the Yangtze River incised-valley near the No.l, No.3 and No.4 Nanjing Yangtze River bridges were established with respective bore date and documents. By ^14C age analysis of the samples of four drilling cores near the No.4 Bridge （to be built）, we can find that the time range of paleo-valley is dated in the LGM at a depth of-60 m to -90 m near Nanjing. It is also indicated that the deep incised-valley channel was narrow and the river flowed swiftly. The ancient Yangtze River deep channel presented partially and deeply incised features near the No.1 Bridge. According to previous publications, much research has been done on the main paleo-channel of the Yangtze River, but few results have been achieved on discharge estimation. In this paper, the incipient velocity and average veIocity of the LGM was calculated with Vc=4.60d^1/3h^1/6, Vc=1.281g（ 13.15. h /d95） √gd, V≈6.5u＊｜h/d90｜^1/6 etc., in terms of the river shape, sedimentary grain size and sequences near the No.3 and No.1 bridges. Moreover, the discharge in Nanjing reach of the Yangtze River during the LGM has been estimated to be around 12,000-16,000 m^3/s according to the relationship of discharge, velocity of flow and cross-section.

The Low Lake-Level Record according to the Selin Co Stratigraphical Basis and Multi-Proxies during the Last Glacial Maximum in the Central Tibetan Plateau

Objective The lake levels in the eastern and southern Asia are regarded as low lake-level owing to precipitation decreasing based on the records of lake-level fluctuation in the continental interior lakes since the last glacial maximum（LGM）（14C 18±1 kaBP,since 20 kaBP）in the Central Asia.Higher lake-level appeared in the transition belt between western Kunlun Mountain and the central Tibetan Plateau.

North Atlantic Abrupt Climate Signals during the Last Glacial Period in Central Asia：Evidences from Aeolian Loess Sediments

Objective Climate fluctuations over suborbital or millennial timescale display significant instability during the last glacial period,which are often superimposed upon the orbital periodicity.They triggered some abrupt climate events,

Possible obliquity-forced warmth in southern Asia during the last glacial stage

Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced~100,000-year global ice-age cycles and monsoon influenced~23,000-year low-latitude hydroclimate variations.However,the shortage of highly-resolved land temperature records remains a limiting factor for achieving a comprehensive understanding of long-term low-latitude terrestrial climatic changes.Here,we report paired mean annual air temperature(MAAT)and monsoon intensity proxy records over the past 88,000 years from Lake Tengchongqinghai in southwestern China.While summer monsoon intensity follows the~23,000-year precession beat found also in previous studies,we identify previously unrecognized warm periods at 88,000-71,000 and 45,000-22,000 years ago,with 2-3℃amplitudes that are close to our recorded full glacial-interglacial range.Using advanced transient climate simulations and comparing with forcing factors,we find that these warm periods in our MAAT record probably depends on local annual mean insolation,which is controlled by Earth’s~41,000-year obliquity cycles and is anti-phased to annual mean insolation at high latitudes.The coincidence of our identified warm periods and intervals of high-frequent dated archaeological evidence highlights the importance of temperature on anatomically modern humans in Asia during the last glacial stage.

Heavy mineral stratigraphy of sediments from the southern outer shelf of the East China Sea since the last glaciation using fuzzy C-means cluster method

Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages, and the sediment sources and depositional dynamics of the environment reconstructed. The assemblages were taken from marine sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea. Based on the variable boundaries of the mineral assemblage at 63 and 228 cmbsf （cm below sea floor）, the core might have previously been divided into three sediment strata marked with units Ⅰ, Ⅱ and Ⅲ, which would be consistent with the divided sediment stratum of the core using minor element geochemistry. The downcore distribution of heavy minerals divided the sedimentary sequence into three major units, which were further subdivided into four subunits. The interval between 0 and 63 cmbsf of the core （unit Ⅰ）, which spans the Holocene and the uppermost late Pleistocene, is characterized by a hornblende-epidote-pyroxene assemblage, and contains relatively a smaller amount of schistic mineral and authigenic pyrite. In comparison, the interval between 63 and 228 cmbsf （unit Ⅱ）, is representative of the Last Glacial Maximum （LGM）, and features a hornblende-epidote-magnetite-ilmenite assemblage containing the highest concentrations of heavy minerals and opaque minerals. However, the interval between 228 and 309 cmbsf （unit Ⅲ）, which spans the subinterglacial period, is characterized by a hornblende-authigenic-pyrite-mica assemblage. Relative ratios of some heavy minerals can be used as tracers of clastic sediment sources. The lower part of the sediment core shows the highest magnetite/ilmenite ratio and relatively high hornblende/augite and hornblende/epidote ratios. The middle core shows the highest hornblende/augite and hornblende/epidote ratios, and the lowest magnetite/ilmenite ratio. The upper part exhibits a slightly higher magnetite/ilmenite ratio, and also the lowest hornblende/augite and hornblende/epidote ratios. The distribution of the mineral ratio is consistent with stratigraphic division in heavy mineral data using correspondence analysis and fuzzy C-means clustering. Variations in heavy mineral association and mineral ratio in core Q43 revealed changes in provenance and depositional environment of the southern outer shelf of the East China Sea since the late Pleistocene, well corresponding to interglacial and glacial cycles.

Precise dating of East-Asian-Monsoon D/O events during 95―56 ka BP:Based on stalagmite data from Shanbao Cave at Shennongjia,China

Based on 23 U/Th analyses and 532 oxygen isotopic data, an averaged 80-a stalagmite oxygen isotopic composition series was established through 95 to 56 thousand years before present (ka BP) from two speleothems in Shanbao Cave, Shennongjia, central China. Shanbao Cave record (referred to as SB record) replicates well with Hulu Cave record, extending the characteristics of millennial oscillations in East-Asian-Summer-Monsoon (EASM) to the past 95 ka. The trend of the SB record generally follows mid-July solar insolation at 65°N, suggesting that mid-high northern latitude insolation, in the first or- der, controls changes of EASM intensity. Millennial oscillations of EASM recorded in the stalagmites are well related to the Greenland interstadials referred to as Dansgaard/Oeschger (D/O) events from 1 to 22, indicating that rapid ocean-atmosphere reorganization in North Atlantic has a remote effect in EASM. The well-dated D/O events by stalagmites probably provide an absolute calibration for chro- nologies of Greenland ice cores. The timings of D/O events in the SB record are different variously from those in Greenland ice cores. For D/O 19 and 20, the age offsets between the stalagmites' and the Greenland ice cores' record are significant, larger than the uncertainties of uranium-series dating. The two events in the SB record are younger than those in North GRIP time scale by 1―2 ka, and older than the counterparts in GISP2 by approximately 3―4 ka. A comparison between the SB and Brazil stalag- mite record shows an anti-phase relation in millennial-scale monsoon precipitation between the two localities. This supports a mode for the coupled ocean-atmosphere "See-saw".