The Eltanin asteroid impact: possible South Pacific palaeomegatsunami footprint and potential implications for the Pliocene–Pleistocene transition     

James Goff  Catherine Chagué‐Goff  Michael Archer  Dale Dominey‐Howes  Chris Turney 《第四纪科学杂志》2012,27(7):660-670

Large asteroid impacts are rare, and those into the deep ocean are rarer still. The Eltanin asteroid impact around 2.51 ± 0.07 Ma occurred at a time of great climatic and geological change associated with the Pliocene–Pleistocene boundary. Numerical models of the event indicate that a megatsunami was generated, although there is debate concerning its magnitude and the region‐wide extent of its influence. We summarise the existing evidence for possible Eltanin megatsunami deposits in Antarctica, Chile and New Zealand, while also examining other potential sites from several locations, mainly around the South Pacific region. In reviewing these data we note that these events were unfolding at the same time as those associated with the Pliocene–Pleistocene boundary and, as such, most of the geological evidence from that time has a climatic interpretation. The potential climatic and geological ramifications of the Eltanin asteroid impact, however, have failed to be considered by most researchers studying this time period. Although we are not advocating that all geological activity at that time is connected with the Eltanin asteroid impact, it raises interesting questions about the role potentially played by such catastrophic events in contributing to or even triggering epochal transitions. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Peat mounds of southwest Tasmania: Possible origins     

M. K. Macphail  M. Pemberton  G. Jacobson 《Australian Journal of Earth Sciences》2013,60(5):667-677

Small mounds of peat rise several metres above the level of the water‐table at Melaleuca Inlet and Louisa Plains on the buttongrass plains in southwest Tasmania. Possible origins of the peat mounds have been explored by pollen analysis and radiocarbon dating of a set of samples taken from a vertical section of one peat mound at Melaleuca. The peat accumulation is entirely of Holocene age although the mound is underlain by sapric peats preserving a cold climate palynoflora of probable Late Pleistocene age. Peats at and near the base of the mound accumulated under a heath sedgeland during the earliest Holocene while after about 7630 a BP the peat‐forming vegetation was shrub‐dominated. The radiocarbon data indicate two main phases of overall peat accumulation, between 7630 and 5340 a BP (Middle Holocene) and between 4450 and 450 a BP (Late Holocene), that were interrupted by a wildfire which burnt into the surface peats. The maintenance of high surface and internal levels of moisture almost certainly was the critical factor behind the low incidence of in situ fires burning into the surface peats on the mound. The perennial influx of groundwater below the mound is a possible origin that fits well with our observations, although the expansion and contraction of soils cannot be discounted as an initiating factor. Enhanced nutrient input from birds may have helped promote growth in the peat‐forming communities. The data do not support the mounds being eroded remnants of a former blanket peat cover or being due to periglacial activity. The peat mounds of southwest Tasmania deserve maximum protection because of their rarity in the Australian landscape and, it seems, elsewhere.  相似文献   

周口店新发现距今11～1.9万年的洞穴堆积层的成因及年代学研究     

田明中  曹伯勋 《现代地质》1993,7(4):421-427

本文对周口店新发现距今11～1.9万年的东岭子洞穴堆积物进行了成因研究,认为该套堆积物并非全属岩溶堆积物,其中也有风成黄土沉积。应用古地磁、热发光及铀系法等年代学方法测定,认为这套堆积为距今11～1.9万年间沉积,弥补了周口店地区近5万年的晚更新世洞穴地层空缺,是一个含有丰富地质事件的晚更新世洞穴地层剖面。  相似文献   

A geomagnetic event recorded in loess deposits of the Tönchesberg (Germany): identification of the Blake magnetic polarity episode     

Jan Reinders  Ulrich Hambach 《Geophysical Journal International》1995,122(2):407-418

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“豫灵人”发现区第四系与古人类相关问题分析     

冯兴祥  张光业  巴志刚  王磐基 《地域研究与开发》1993,(Z1)

本文通过对“豫灵人”发现区地壳发展历史和第四系成因类型的分析,提出了“豫灵人”发现区古人化石所在地的中更新统上部地层是本区继续寻找发现古人化石和旧石器的重要地区与地层之一。  相似文献   

昆明草海晚更新世硅藻植物群及其环境演化   总被引：3，自引：0，他引：3  

张茂恒  黄巧华 《云南地理环境研究》1993,5(1):55-64

通过对草海2号孔硅藻植物群生态演化及沉积特征的研究,将草海晚更新世划分为十个硅藻带和五个环境演化段落,说明5万年以来草海经历了由河流三角洲—中深湖滨—浅湖—沼泽的发展过程,在距今4.4万年时,滇池湖达到高潮,以后一直湖退,其中距今2.8万年左右由于河口砂坝的发展而形成海埂,使草海与滇池相对隔离而进入一个独立发展阶段,并加快了草海沼泽化进程。从气候上看,5万年以来,草海也经历了凉—暖—凉—温的两次周期性变化。  相似文献   

湖北省钟祥第四纪冰缘融冻构造的发现及其意义   总被引：3，自引：0，他引：3  

陈华慧  关康年 《现代地质》1990,4(2):92-97

笔者于1986年在钟祥首次发现了第四纪地层间的冰缘融冻构造——古冰楔与揉皱,其时代为早更新世末期—中更新世初期。它的发现不仅为建立本区第四纪地层层序,而且为确定更新世北方冰缘冻土的南界和研究长江中下游更新世古气候环境的演变提供了重要的科学依据。  相似文献   

湖北黄岗晚更新世孢粉动态组合的统计分析及古气候性质   总被引：1，自引：1，他引：1  

田明中  曹伯勋 《地球科学》1990,15(5):505-513

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松嫩平原晚第三纪—更新世孢粉组合及古植被与古气候的研究   总被引：9，自引：0，他引：9  

夏玉梅  汪佩芳 《地理学报》1987,(2)

本文通过大庆、乾安、长春、哈尔滨等地所揭示孢粉资料,试将松嫩平原晚第三纪到更新世时期划出13个孢粉带。根据孢粉组合系列变化和磁性地层测定,论述古植被与古气候演化过程,为研究东北平原第四纪自然环境变迁提供科学依据。  相似文献   

松辽分水岭东段白土山组成因与时代   总被引：3，自引：1，他引：3  

王庆  杨景春 《地层学杂志》1995,19(4):287-290

综合考虑松辽分水岭东段地区白土山组的地层分布、沉积特征、地貌部位及第四纪以来松辽分水岭的演化过程、松辽水系的变迁，认为其为河流冲积物，形成时代为早更新世早期。  相似文献