珠江三角洲MIS 5间冰期海平面波动新证据

珠江三角洲第四系广泛发育沉积间断,致使该区域的古环境重建仍然存在诸多疑问,特别是对全新统以下的沉积旋回发育时代及其反映的海平面变化历史等争议尚大。近年从珠江三角洲中部平原钻取的一个长50多米的岩芯中,首次在第四纪地层中见到6个明显的红色沉积层,综合利用沉积学、年代学及区域对比分析后认为,该套地层包含了MIS6以来的沉积,6个红色沉积层中,除最顶部红色层为末次冰期(MIS4～2)形成的典型花斑粘土层外,其余5个红色层均应为MIS5间冰期海平面阶段性降低的沉积产物,反映在MIS5海侵过程中海平面有过多次显著波动。地球化学和矿物学分析结果进一步指示,自下而上6个红色沉积层经受过的化学风化作用强度增大,指示MIS5以来研究区相对水面波动降低的幅度和(或)持续时间从早期到晚期呈增加趋势。     

Sedimentology,palaeoecology and geochronology of Marine Isotope Stage 5 deposits on the Shetland Islands,Scotland

New stratigraphical, palynological and dating evidence is presented for pre‐Late Devensian/Weichselian sediments at Fugla Ness and Sel Ayre, Shetland. The Fugla Ness Peat rests on till and formed during an interglacial that saw the development of maritime heaths, with scattered trees and shrubs, including Pinus and possibly Ilex. A decline into stadial conditions is marked by overlying periglacial breccia and till. The Sel Ayre Organic Sands and Gravels lie between periglacial breccias and beneath till and appear to record a changing interstadial environment in which trees were absent and the vegetation comprised largely heaths, with Bruckenthalia, and grasslands. The Fugla Ness Peat is dated to 110+40/?35 ka by uranium series disequilibrium, suggesting that it formed during the Ipswichian/Eemian Interglacial (Marine Isotope Substage 5e). Luminescence ages of ca. 98–105 ka on intercalated sands within the Sel Ayre Organic Sands and Gravels place these deposits in Marine Isotope Substage 5c (Brørup Interstadial). The two sites provide the first detailed record of Marine Isotope Stage 5 environments on Shetland. Copyright © 2002 John Wiley & Sons, Ltd.     

Climatic Character of Marine Isotope Stage (MIS) 5e in the Representative Regions of the World: A Review

The Last Interglacial or Marine Isotope Stage (MIS) 5e, is of great interest because it serves as an analog for the Holocene. The climate change and duration during Marine isotope stage (MIS) 5e are considerably well understood for recent and future climate. Despite great interest in this subject over many years, a number of issues concerning the climate circumstances of MIS 5e are by no means resolved. We analyzed 35 published palaeoclimate records with reliable chronologies and robust proxies in typical region of the world to evaluate climate change during MIS 5e. These data indicate that: ① The duration of this warm phase is thought to range from (128±2) ka to (116±2) ka. The climate of MIS 5e was likely relatively stable with a number of abrupt, weak amplitude, cool and/or arid events. And the difference between regions is noticeable for the occurrence, amplitude, onset and duration of these events. For example, marine records from the North Atlantic indicate that the climate of MIS 5e was relatively stable, however the records from Norwegian sea show that the climate of MIS 5e had a significant changes at the beginning and cold event in the Mid-Eemian; The δ¹⁸O, δD and CH₄ in the ice cores from Greenland and Antarctica imply that climate was relatively stable during the last interglacial period, while in Europe from the north to the south the duration of this phase became shorter and the intensity of climatic events became stronger. In addition, the climatic conditions of MIS 5e reconstructed by climate proxy from China are various and have the subject of some controversy. ②The global climate response to the insolation forcing would have been uniform on suborbital timescale. Nevertheless, as a result of regional sundry climatic forcing factors, global millennial-scale/century-scale climate oscillations were marked by significant local features during stage 5e. ③ Based on the better chronological controls, the estimation of climate parameters, the high-resolution climate records, and precise knowledge of the phase relationship between climate changes in global, the earlier depiction for climate circumstances and environment change during Marine Isotope Stage 5e should be refined and our understanding of the climate dynamics and mechanism and climate modelling should be improved.     

Climate variability in the Salawusu River valley of the Ordos Plateau (Inner Mongolia,China) during Marine Isotope Stage 3

Fluctuations in climatic proxies of the Milanggouwan section in the Salawusu River valley of the Ordos Plateau (Inner Mongolia, China) during Marine Isotope stage 3 (MIS 3) coincide well with sedimentary cycles for palaeo‐mobile dune sands alternating with fluvial–lacustrine facies and palaeosols. We compared the palaeo‐mobile dune sands with modern mobile dune sands (products of a cold and dry climate dominated by the East Asian winter monsoon), whereas the fluvial–lacustrine facies and palaeosols were controlled by a wet–warm climate similar to that of the East Asian summer monsoon. The MIS 3 climate of the Salawusu River valley appears to have experienced at least nine wet–warm and ten cold–dry fluctuations, divided into five stages: MIS 3e (58 900–49500 yr BP), MIS 3d (49 500–40 700 yr BP), MIS 3c (40 700–36 900 yr BP), MIS 3b (36 900–27 000 yr BP) and MIS 3a (27 000–22 300 yr BP). The 19 cold–warm climatic fluctuations corresponded roughly to the GRIP and Guliyan records, and with fluctuations in the North Atlantic climate. Notable peaks in the spectral analysis occurred at 19 500 yr, 1020 yr, 640 yr and 500 yr. Our results show that the millennial–centennial climate was closely related to the relative strengths of East Asian monsoons, which are controlled by the North Atlantic thermohaline circulation, and which is also closely linked to the Sun's precession period. Copyright © 2008 John Wiley & Sons, Ltd.     

Phase relationship and surface water mass change in the Northeast Atlantic during Marine Isotope Stage 11 (MIS 11)

Planktic foraminiferal census data, faunal sea surface temperatures (SSTs) and oxygen isotopic and lithic records from a site in the northeast Atlantic were analyzed to study the interglacial dynamics of Marine Isotope Stage (MIS) 11, a period thought to closely resemble the Holocene on the basis of orbital forcing. Interglacial conditions during MIS 11 persisted for approximately 26 ka. After the main deglacial meltwater processes ceased, a 10- to 12-ka-long transitional period marked by significant water mass circulation changes occurred before surface waters finally reached their thermal maximum. This SST peak occurred between 400 and 397 ka, inferred from the abundance of the most thermophilic foraminiferal species and was coincident with lowest sea level according to benthic isotope values. The ensuing stepwise SST decrease characterizes the overall climate deterioration preceding the increase in global ice volume by  3 ka. This cooling trend was followed by a more pronounced cold event that began at 388 ka, and that terminated in the recurrence of icebergs at the site around 382 ka. Because the water mass configuration of early MIS 11 evolved quite differently from that of the early Holocene, there is little evidence that MIS 11 can serve as an appropriate analogue for a future Holocene climate, despite the similarity in some orbital parameters.