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甘肃临夏盆地中新世地层及哺乳动物化石 被引量:7
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作者 张行 《兰州大学学报(自然科学版)》 CAS CSCD 北大核心 2001年第2期123-130,共8页
甘肃临夏地区中新世哺乳动物化石引起学术界的重视 .经过考察、发掘 ,发现了大量的化石标本 .由于发表的文章多为单篇 ,较分散 ,笔者收集整理 ,对材料进行了研究 ,认为甘肃临夏地区在近十余年来是全国发现中新世材料最多的地区 ,且有极... 甘肃临夏地区中新世哺乳动物化石引起学术界的重视 .经过考察、发掘 ,发现了大量的化石标本 .由于发表的文章多为单篇 ,较分散 ,笔者收集整理 ,对材料进行了研究 ,认为甘肃临夏地区在近十余年来是全国发现中新世材料最多的地区 ,且有极高的研究价值 。 展开更多
关键词 甘肃临夏盆地 中新 哺乳动物化石 中新世地层 化石标本
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澳大利亚十二门徒中新世地层成因研究 被引量:3
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作者 吴海斌 刘秀铭 +5 位作者 吕镔 马明明 吉金平 王文艳 章余银 侯吉立 《第四纪研究》 CAS CSCD 北大核心 2017年第1期82-96,共15页
澳大利亚维多利亚州南部海岸坎贝尔港(Port Campbell)附近的十二门徒(The Twelve Apostles)地层主要为石灰质地层,偶见海相生物贝壳,一直被认为是浅海大陆架石灰岩(limestone)沉积。野外考察发现,该地层不仅存在海相生物碎片... 澳大利亚维多利亚州南部海岸坎贝尔港(Port Campbell)附近的十二门徒(The Twelve Apostles)地层主要为石灰质地层,偶见海相生物贝壳,一直被认为是浅海大陆架石灰岩(limestone)沉积。野外考察发现,该地层不仅存在海相生物碎片,同时也存在根化石、钙结核层等地表古土壤特征。为了更好地分析其沉积环境,本文对十二门徒剖面样品的粒度、石英颗粒表面形态以及稀土元素进行了系统分析,并将其结果与第四纪西峰黄土古土壤和现代海滩砂进行比较。结果表明,整个剖面序列以细粉砂为主,与典型风积黄土古土壤具有相似的粒度分布与粒度象特征,Sahu判别分析结果表明绝大部分样品值都小于-2.7411,显示了剖面整体以风积成因为主。样品的石英颗粒呈现出不规则的棱角状、次棱角状,显示风成特征;此外,十二门徒剖面样品具有与黄土古土壤以及上地壳(UCC)相似的稀土元素分配模式。因此,我们认为该地层并非海相石灰岩沉积,而是一套在半干旱气候条件下发育的具有多层钙结核的风积序列地层。该地层记录了澳洲东南海岸16.0-5.3Ma以来的风积历史与气候变化,表明澳大利亚的干旱化至少是在16Ma前就开始了。由于这套风积地层靠近海岸,易受地质时期海平面变化的影响,以致在地层中的局部层位出现海相生物碎屑,但地层的物质来源可能来源于澳大利亚的艾尔湖(Lake Eyre)盆地。 展开更多
关键词 澳大利亚 十二门徒 中新世地层 风成成因
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Prehistoric Earthquakes in the Chishan Segment of the Tancheng-Lujiang Fault Zone during the Mid-Late Pleistocene
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作者 Yao Daquan Tang Youbiao +7 位作者 Shen Xiaoqi Chen Anguo Zheng Haigang Zhao Peng Xiao Weipeng Li Guang Zheng Yinping Li Lingli 《Earthquake Research in China》 2012年第4期491-498,共8页
Chishan is located in Sixian County of Anhui Province, and the west branch fault of Tancheng-Lujiang fault zone passes through here. According to previous research, the Chishan segment of Tancheng-Lujiang fault zone h... Chishan is located in Sixian County of Anhui Province, and the west branch fault of Tancheng-Lujiang fault zone passes through here. According to previous research, the Chishan segment of Tancheng-Lujiang fault zone has been obviously active since the Quaternary. Trenches excavated perpendicular to the Chishan segment for this study have revealed many prehistoric earthquake ruins--the multi-phase reverse faulting colluvial wedge, which is represented as the western brick-red sandstone of the late Cretaceous or maize gravel stratum of the mid Pleistocene of the hanging wall of the fault overlapping eastward the mid-late Pleistocene brown clay. In the base of the wedges, steep NW-dipping faults were found, and the steep fault planes turned upward to gently dipping collapse planes. As revealed by the trenches, the connection line of the breaking points strikes NNE in general. Heaving landforms are preserved at most parts of the tailing edge of the hanging wall where the fault passes through, and some EW-trending gullies were offset by right- lateral faulting. The two walls of several trenches have consistently shown that the collapse of traces have been pushed by a west-to-east force. Among them, Tcl - Tc4 show that the brick red limestone (K2 ) overthrust and collapsed on the yellow-brown clay containing ferro-manganese nodules ( Q2r-3 ) ; Tc5 reveals that the yellowish-white gravel ( Q2r ) and the sandstone (K2 ) and overthrust and collapsed on the aforementioned clay. Reverse faulting colluvial wedges are found on both walls of each of the 8 trenches, but the number of wedges revealed in different trenches is different: there is 1 wedge, and 2 wedges in Tcl and Tc3. 3 wedges in Tc2, Tc4 and Tc5, and in individual trenches, few wedges are revealed. This may be related to the trench's location, depth and height of theremaining denudation. From the analysis of the trenches and the thermoluminescence dating results, we can preliminarily conclude that multiple large-scale reverse faulting stick events have taken place on the Chishan segment of the Tancheng-Lujiang fault zone during the mid-late Pleistocene, that is to say, many pre-historie strong earthquakes have occurred. 展开更多
关键词 Tancheng-Lujiang Fault zone Chishan Mid-late Pleistocene Prehistoricearthquake
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Holocene delta evolution and sequence stratigraphy of the Pearl River Delta in South China 被引量:13
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作者 WEI Xing WU ChaoYu 《Science China Earth Sciences》 SCIE EI CAS 2011年第10期1523-1541,共19页
We analyzed the sedimentary characteristics and chronostratigraphy of the Pearl River Delta in South China, and discussed the Holocene stratigraphic characteristics and the filling process since the Holocene, based on... We analyzed the sedimentary characteristics and chronostratigraphy of the Pearl River Delta in South China, and discussed the Holocene stratigraphic characteristics and the filling process since the Holocene, based on 90 boreholes. Our results showed that the maximum transgressive surface of the Pearl River Delta was located in the soft marine silt horizons, whereas it was shown as an erosion surface in areas with tidal scour. From bottom to top, Holocene sedimentary sequences were fluvial facies, floodplain-estuary facies, and estuary-delta facies in the paleo-valley, while the paleo-interfluve sequences were described as littoral facies, estuary facies, and delta facies. Vertical accumulation sequences of Holocene sediments were shown primarily as positive tapering-shaped sequences with no typical foreset, topset, or other sedimentary sequences of the Gilbert Delta. The paleo-Pearl River estuary had different evolution models in the highstand systems tract (HST) compared with other large deltas worldwide, in that it is dominated by a unique and complex geomorphologic boundary, and that it is a multi-sourced delta compounded by the independent and parallel development of fluvial sedimentary bodies with different scales. A huge estuary was formed in the present Pearl River Delta area when the post-glacial transgression reached maximum at about 6 ka BP. The estuary was divided into two parts by obstruction of a series of islands, an upper part composed of the semi-enclosed inner paleo-bay connected to rivers and a lower part consisting of the outer paleo-bay connected to the ocean. Both of these areas were interlinked by only a few narrows, in which the fluvial sediments are accumulated primarily in the inner paleo-bay. During 6-2 ka BP, the sedimentation in various regions of the inner paleo-bay occurred simultaneously with independent development under the remodeling and transformation effect of complex boundaries on river and ocean dynamics. After 2 ka BP, the evolution of the delta is no longer a simple natural process, but rather a common remodeling process accomplished by nature and humans. 展开更多
关键词 Pearl River Delta HOLOCENE stratigraphic framework delta evolution
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