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41.
Paul F. Karrow Arthur L. Bloom Andreas G. Heiss Barry B. Miller Alan V. Morgan 《Quaternary Research》2009,72(1):132-142
The Fernbank interglacial site, on the west side of Cayuga Lake, New York, has been recently subjected to more detailed study. To a lengthened mollusc list are added ostracodes, insects, fish, pollen, and plant macrofossils. Of these, plants are well preserved and diverse, whereas other groups are poorly preserved and incomplete. Nevertheless, all support the interglacial assignment (Sangamon), which is further supported by minimum age radiocarbon dates (> 50,000 14C yr BP) and a TL date of 81 ± 11 ka. In the plant record near the top of the sequence, abundant tree charcoal indicates forest fires. Like the Toronto interglacial record, the plants show a declining July mean temperature from 24 to 18°C (according to transfer functions) through the sequence, from mixed deciduous forest to boreal forest. 相似文献
42.
末次间冰期以来渭河上游气候演化的黄土记录研究 总被引：1，自引：1，他引：0
对渭河上游樊家台剖面末次间冰期以来黄土地层的粒度与CaCO3进行综合分析表明,末次间冰期时,受夏季风影响较大,粒度较细,CaCO3有较强的淋溶与淀积,气候呈现较为暖湿的特点;末次冰期时,受冬季风影响较强,粒度较粗,CaCO3淋溶淀积微弱,气候较为干冷。间冰期早期（相当于深海氧同位5e阶段）由于夏季风较强,粉尘堆积较少,古土壤向下发育,并与下部土壤融合,导致粒度较5a、5c阶段粗;2阶段的早期,由于粉尘源区出现了高湖面,环境湿度大,造成此时段早期黄土粒度较晚期细;表现出区域气候的特点。 相似文献
43.
Highstands in the Marine Isotope Stage (MIS) 3 based on 14C dating in the Qinghai–Tibetan Plateau (QTP) are widely documented. Recent records from shoreline sediments dated using U‐series and/or optically stimulated luminescence (OSL), however, reveal that the highstands originally dated in MIS 3 should now be considered to fall in MIS 5. This paper provides new evidence from the interior of the QTP, based on the grain‐size from a continuous lake core in the Zabuye Salt Lake, to verify the MIS 5 highstand in the QTP. Grain‐size analysis of the core sediments also distinguishes two other highstands in MIS 3 and MIS 2, respectively. The MIS 5 highstand is considered as the maximum lake level since the Last Interglacial, as cored sediments contain very low values of Median Diameter (Md) during MIS 5. Compared with the discontinuous records from lake shorelines sediments, the grain‐size records from the continuous lake centre core sediments provide a more complete dataset to infer lake level variations, and make it possible to make wider palaeoclimatic and palaeoenvironmental interpretation. In the interior of the QTP, highstands might have continued into cold climate periods due to the reduced evaporation rates in the latter. The influence of the moisture‐bearing southerly‐shifted Westerly wind pathway may also have contributed to the highstands in the glacial period. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
44.
末次间冰期我国半干旱盆地Rb、Sr的迁移聚集规律与环境演变——以萨拉乌苏河流域米浪沟湾剖面研究结果为例 总被引：2，自引：0，他引：2
萨拉乌苏河流域米浪沟湾剖面末次间冰期层系记录了8.5个有风成的古沙丘砂与河湖相和/或古土壤构成的沉积旋回。该层系Rb、Sr元素含量分布具有明显的规律,主要表现为古沙丘砂中的Rb、Sr含量相对迁移,而在上覆河湖相和/或古土壤中相对聚集,构成末次间冰期的Rb、Sr含量迁移与聚集的8.5个元素旋回。研究表明,由Rb、Sr含量变化构成的这些旋回主要是由干冷暖湿气候波动所致。该地末次间冰期层系由上至下可划分为5个层段,即MS1~MS5。Rb、Sr含量在MS1、MS3、MS5和MS2、MS4分别呈现明显的峰态和不同程度的低谷,揭示出前者与后者分别是受到暖湿和干冷气候影响的阶段。据此,可以将 MS1、MS2、MS3、MS4和MS5依次在气候性质和阶段上可与GRIP冰芯和Sulu 海MIS5a、5b、5c、5d、5e诸亚段进行对比。研究亦表明,河湖相和古土壤Rb/Sr曲线却都不尽是峰态,黄土高原Rb/Sr值的气候意义并不完全适宜说明半干旱盆地或洼地的古环境变化。 相似文献
45.
Elisa Sainz de Murieta Pedro P. Cunha Alejandro Cearreta Andrew S. Murray Jan-Pieter Buylaert 《第四纪科学杂志》2021,36(4):570-585
A detailed study is presented of a 15.3-m-thick Pleistocene coastal terrace located on the Cantabrian coast (northern Spain). Stratigraphic, sedimentological, topographic and micropalaeontological information is combined with a chronology based on luminescence dating to characterize the deposits. The sedimentary succession records: (i) a basal transgressive system, consisting of a wave-cut surface covered by a lower layer of beach gravels and upper beach pebbly sands; and (ii) a thicker upper highstand system (aggrading), comprising medium to very fine aeolian sands interbedded with thin palustrine muds. Luminescence dating involved a detailed sampling strategy (36 samples and two modern analogues) and the use of both quartz optically stimulated luminescence (OSL) and feldspar post-infrared infrared stimulated luminescence single aliquot regeneration protocols; feldspar results were used to confirm the completeness of bleaching of the quartz OSL signal. The quartz OSL luminescence age–depth relationship shows significant dispersion, but nevertheless two rapid phases of deposition can be clearly identified: one at ~130 ka [Marine Oxygen Isotope Stage (MIS) 5] and one at ~100 ka (MIS 5c). The top of the succession is dated to ~70 ka. The MIS 5e marine maximum flooding surface is identified at an elevation of 6.85 m above mean seal level. This elevation provides evidence of a regional sea-level highstand for this sector of the Cantabrian coast. 相似文献