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81.
用天文方法建立商后期甲骨文年代序列的新途径—解析殷历月法 总被引:8,自引:2,他引:6
利用对具有月龄特征的历谱规律的研究成果,以推定甲骨文的绝对年代,从而提供了建立商后期甲骨文年代序列的新方法,并给出了13版卜辞的例证,通过分析殷历月的结构,得出殷历中“二癸月”和“四癸月”的月首分别为首甲日和首癸日,初步归纳出殷历月法,月首为初三,月长等于逆望月周期,建立固定,且找到建立丑之例,置闰规律未知,已存在年终,年中置闰两种闰法。 相似文献
82.
Lubbock Lake (Southern High Plains of Texas) contains a cultural, faunal, and floral record within a virtually complete geological record spanning the past 11 100+ years. More than 88 archaeological occurrences have been excavated from five major stratigraphic units. The Paleoindian record (11 500–6500yr BP) begins with Clovis-age occupation (ca. 11 100yr BP) found within fluvial deposits (stratum 1). Subsequent Paleoindian occupations are found in lake and marsh sediments (stratum 2). Archaic occupations (8500-2000yr BP) are contained within aeolian and marsh deposits (strata 3 and 4). Ceramic occupations (2000-500yr BP) are found on a soil developed in stratum 4, in marsh sediments (strata 4 and 5), and in slopewash and aeolian sediments (stratum 5). The Protohistoric (500-300yr BP) and Historic (300-100yr BP) remains are in slopewash, aeolian, and marsh sediments (stratum 5) and associated soils. The Southern High Plains remained a grasslands throughout the last 11 500 years and neither man nor bison abandoned the region. The successive local faunas reflect changing ecosystems under pluvial to arid to more mesic to semiarid conditions. The occupation of Lubbock Lake through time appears to have been by small groups of people for both economic and short-term residential uses. These hunter-gatherer peoples underwent adaptive change brought about by climatic stress and alterations to food resources. 相似文献
83.
Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5
± 0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched
mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make
clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5 ± 0.2 Ma in the Mangkang
basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet
distinguished by Wang J. H. et al., implying that they were formed in the same tectonic setting. 相似文献
84.
The aeolian sedimentation record of the Thar desert 总被引:1,自引:0,他引:1
A review of the aeolian sedimentary record of the Thar desert is presented. This includes a regional survey of the major dune
forms, their genesis and their relationship to climate and other regional landforms. A key aspect of this work is the chronometry
of the dunes using luminescence methods. Luminescence dating of sand has enabled quantification of the duration of the phases
of sand aggradation and quiescence, time scales of dune migration and the dating of pedogenic carbonates. We demonstrate that
the conventional wisdom of synchronicity of dune aggradation with glacial epoch is not true in the context of Thar sands and
here only a short durationwindow of opportunity existed for dune aggradation. Luminescence ages further suggest that this window occurred during a transitional climatic
regime from glacial to interglacial about 4–10 ka after the glacial epoch. Other inferences included are that:
相似文献
– | • the aeolian activity in the Thar began over > 150 ka, resolving that Thar is not of anthropogenic origin as suggested previously; |
– | • the present spatial extent of the aeolian activity in the Thar is in a contracted stage compared to that in the geological past, which refutes the arguments on its rapid north-eastward expansion; |
– | • the current dune migration rates in areas of significant human-induced disturbances are much higher than during the geological past; |
– | • the monsoon activity in the Thar varied significantly, from being minimal during the isotopic marine stages 4 and 2 to being close to the present during stage 3; |
– | • on shorter time scales the dune activities correlated with the lacustrine records of the region with a phase difference of a few centuries and a periodicity of ∼ 1500 years; |
– | • the sand aggradation climate in the southern margin in Gujarat gradually shrank northwards such that in general dunes older than 10 ka are seen in the extreme southern margin and dunes younger than 2ka ages occur mostly in the western part of Rajasthan. |
85.
The correlation between specific activities of some natural radionuclides (238U, 226Ra, 232Th, 40K) measured in sediment taken from river bottom was studied. The sediment was taken from the Serbian part of the Danube River. Good correlation between some of the isotopes is observed, so that their specific activity ratios are spread over a lower range than specific activities themselves. This suggests that evaluation of specific activity ratios of some natural radionuclides could be a more sensitive method for the determination of increased levels of some of them than the straightforward analysis of specific activities. 相似文献
86.
87.
Xu Peng Yixin Chen Gengnian Liu Beibei Liu Yingkui Li Qing Liu Yesong Han Weilin Yang Zhijiu Cui 《第四纪科学杂志》2019,34(1):40-50
88.
89.
那丹哈达增生杂岩为中国东部古太平洋板块俯冲最为可靠的地质记录之一,对限定古大洋板块的西向俯冲具有重要的理论意义.饶河杂岩位于那丹哈达增生杂岩的核心位置,发育典型的增生杂岩组合,其中玄武岩类多呈构造透镜体状产出于超镁铁质-镁铁质杂岩带,变形轻微,没有遭受变质.对饶河杂岩中枕状玄武岩样品进行的同位素年代学和地球化学研究结果表明:饶河杂岩中枕状玄武岩锆石LA-ICP-MS U-Pb年龄为中侏罗世(168±2 Ma),枕状玄武岩大离子亲石元素Rb、Sr亏损,高场强元素Nb、Ta富集,Th元素丰度较高,形成于洋岛(OIB型)环境.饶河杂岩中枕状玄武岩的形成时代和成因环境,对于该区侏罗纪时期构造动力学背景研究具有意义. 相似文献
90.
Jessey M. Rice Martin Ross Roger C. Paulen Samuel E. Kelley Jason P. Briner Christina M. Neudorf Olav B. Lian 《第四纪科学杂志》2019,34(7):519-535
The Laurentide Ice Sheet was characterized by a dynamic polythermal base. However, important data and knowledge gaps have led to contrasting reconstructions in areas such as the Labrador Ice Divide. In this study, detailed fieldwork was conducted at the southeastern edge of a major landform boundary to resolve the relative ice flow chronology and constrain the evolution of the subglacial dynamics, including the migration and collapse of the Labrador Ice Divide. Surficial mapping and analysis of 94 outcrop‐scale ice flow indicators were used to develop a relative ice flow chronology. 10Be exposure ages were used with optical ages to confine the timing of deglaciation within the study area. Four phases of ice flow were identified. Flow 1 was a northeasterly ice flow preserved under non‐erosive subglacial conditions associated with the development of an ice divide. Flow 2 was a northwest ice flow, which we correlate to the Ungava Bay Ice Stream and led to a westward migration of the ice divide, preserving Flow 2 features and resulting in Flow 3's eastward‐trending indicators. Flow 4 is limited to sparse fine striations within and around the regional uplands. The new optical ages and 10Be exposure ages add to the regional geochronology dataset, which further constrains the timing of ice margin retreat in the area to around 8.0 ka. Copyright © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd. 相似文献