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1.
过去认为涝池河—阳郭动物群的时代相当或稍晚于泥河湾动物群,早于公王岭动物群,厚镇涝池河动物群的时代与公王岭动物群的一致。但各动物群的层位及在动物群演化上所处的位置表明涝池河—阳郭动物群的时代应与公王岭动物群的一致,比泥河湾动物群的晚,而厚镇涝池河动物群的时代应与陈家窝动物群的相当。重新厘定了公王岭期与陈家窝期的涵义,认为蓝田黄土地层中、早更新统的界线应划在Ｓ８与Ｌ９交界处。 相似文献
2.
通过中国北方５．３０Ｍａ以来含丰富哺乳动物化石的典型剖面的磁性地层研究,建立５．３０Ｍａ以来中国北方陆相哺乳动物群与磁性地层序列对比。中国黄土记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带,黄土年龄约２．５０ＭａＢ．Ｐ．,其中发现有午城动物群、公王岭动物群、阳郭动物群、陈家窝动物群与靖远动物群。三门组记录了Ｍａｔｕｙａｍａ负极性带下段,年龄约１．２０—２．５０Ｍａ,其中发现有三门动物群。静乐剖面的静乐红土对应于Ｇａｕｓｓ正极性带上段,年龄约２．５０—３．００Ｍａ,其中发现有静乐贺丰动物群。游河组记录了Ｇａｕｓｓ正极性带,年龄约２．５０—３．４０Ｍａ,其中发现游河动物群。泥河湾沉积对应于Ｂｒｕｎｈｅｓ正极性带、Ｍａｔｕｙａｍａ负极性带、Ｇａｕｓｓ正极性带,年龄约０．１３—３．４０Ｍａ。其中小长梁剖面记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带上段（含Ｊａｒａｍｉｌｏ亚带）,年龄约０．１３—１．００Ｍａ（其中含化石及石器地层年龄约０．９０—１．００Ｍａ）。榆社盆地麻则沟组记录了Ｇａｕｓｓ正极性带（２．５０—３．４０Ｍａ）,高庄组记录了Ｇｉｌｂｅｒｔ负极性带（３．４０—５．３０Ｍａ）。 相似文献
3.
4.
对泥河湾动物群(狭义)与欧洲维拉方经典动物群中属级相同的２０种哺乳动物进行形态和进化水平上的对比发现,其中有１１种(包括亚种)和晚维拉方期的 Ｏｌｉｖｏｌａ动物群的成员最接近,有４种可与中维拉方晚期的Ｓｅｎｅｚｅ动物群的成员比较,其中有２种因为仅发现于Ｓｅｎｅｚｅ,不足以说明它们一定只和泥河湾者接近。另外两种(Ｌｙｎｘ ｓｈａｎｓｉｕｓ和Ｐｓｅｕｄｏｄａｍａｅｌｅｇａｎｓ)确实和Ｓｅｎｅｚｅ者更接近而不同于Ｏｌｉｖｏｌａａ者。有两种动物(Ｂｏｒｓｏｄｉａ ｃｈｉｎｅｎｓｉｓ和Ｍｅｌｅｓ ｃｈｉａｉ)间接地表明泥河湾动物群可能和 Ｏｌｉｖｏｌａ更接近。还有 ３种时代意义不大。总之,对比表明泥河湾动物群(狭义)与欧洲晚维拉方早期的Ｏｌｉｖｏｌａ动物群最为接近,其年代应为１８Ｍａ左右,接近于海相Ｖｒｉｃａ剖面更新世／上新世界线(１．７９６Ｍａ)。 相似文献
5.
应用古地磁研究云南古猿的生存年代 总被引：2，自引：0，他引：2
应用古地磁研究方法，对我省出土古猿化石的开远小龙潭煤系，禄丰石灰坝的砂、砾石、褐煤层及元谋竹棚、小河一带的砂、泥质层作了系统的古地磁采样测试得出：（１）开远小龙潭煤系及动物群化石的时代为５．１０－１０．００Ｍａ，其中，开远古猿产出层位的年代为８．３０±０．１０Ｍａ。（２）禄丰石灰坝含古猿及哺乳动物化石的一套砂、砾石、褐煤的时代为３．８９－４．５９Ｍａ，禄丰古猿化石产出层位的年代为４．００±０．１０Ｍａ。（３）元谋竹棚、小河一带古猿化石及动物群的地层时代为２．１２－３．４０Ｍａ，其中元谋蝴蝶古猿的时代为２．７６±０．１０Ｍａ，竹棚猿人的年代为２．１３±０．１０Ｍａ。上述古猿的地质年代为晚中新世一早更新世。云南古猿的演化，从开远小龙潭到禄丰石灰坝直至元谋竹棚、小河一带，在时间和地点上构成了一连续的演化序列。云南古猿生存年代的进一步确定，对研究人类的起源、演化及寻找人类的祖先有着重要的科学意义。 相似文献
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中华鸟龙与孔子鸟类的时代：辽西义县组火山凝灰灰岩激光^40Ar^39Ar？… 总被引：18，自引：1，他引：17
利用Ｎｄ－ＹＡＧ激光Ａｒ－Ａｒ测年法,对产自辽西北票四合屯－尖山沟地区义县组底部孔子鸟和中华鸟龙湖相层中火山凝灰岩中的黑云母单晶帮了５０多次分析,得出的同位素年龄值为（１４７±１．８）Ｍａ,用Ｋ－Ａｒ法测得孔子鸟化石外面的火山包裹层的结果为９１４７．３×３．３）Ｍａ,两者年龄时代相当吻合,同为晚朱罗世晚期（晚提唐朝）,比德国始祖鸟层的时代略晚,也与了鸟特征和美颌龙类－中华鸟龙指示的地质时代吻合。 相似文献
7.
晋宁期后华南陆壳增生作用—海相碳酸锰矿的Nd同位素制约 总被引：2，自引：0，他引：2
扬子地台南缘早震旦世，古生代和晚三叠世海相碳酸锰矿石的εＮｄ（Ｔ）值分别是－４．６－－５．５，－８．１－－９．０和－３．５－－４．２。Ｚ１－Ｃ１期间，它们的Ｎｄ模式年龄Ｔ２ＤＭ平均为１９３１±４６Ｍａ，εＮｄ（Ｔ）－Ｔ演化线与亏损地幔演化线交点年龄为１９５０Ｍａ，ｄ（Ｔ）／ｄσ＝０．９６。Ｎｄ同位素组成特征表明：华南陆壳晋宁期前的增生作用主要发生在早元古代的１９３１±４６Ｍａ前，晚元古代地壳增生作 相似文献
8.
阳郭黄土剖面有机组分变化的周期性与古气候变迁因素 总被引：1，自引：0，他引：1
渭南阳郭黄土剖面是迄今发现的１５万年以来较完整的剖面之一，作者对出阳郭剖面中的有机质指标进行了概率分布与谱分析计算，得出它们的概率分布类型及四个稳定的周期：６７．１Ｋａ，３３．５Ｋａ，２５．２Ｋａ和１８．３Ｋａ。这四个周期与洛川黄土剖面中元素组分变化的短周期基本一致。 相似文献
9.
扬子南缘沉积岩的Nd同位素演化及其大地构造意义 总被引：36，自引：5，他引：36
本文系统分析了扬子块体南缘中元古代到二叠纪各个时代地层中泥质沉积岩的Ｓｍ－Ｎｄ同位素组成。中元古代（１．６～１．ＯＧａ）沉积岩具有一致的Ｎｄ模式年龄（ｔＤＭ）（≈１．８Ｇａ）；晚元古代早期（０．９～０．７７Ｇａ）沉积岩的ｔＤＭ年龄从≈１．８Ｇａ急剧降低至。１．３Ｇａ；震旦纪晚期到二叠纪（０．６６～０．２７Ｇａ）沉积岩的ｔＤＭ年龄又恢复到大约１．８Ｇａ。晚元古代早期沉积岩ｔＤＭ年龄的显著降低，表明这个时期扬子南缘的沉积物源区加入了大量新的幔源物质。沉积岩的Ｎｄ同位素结果对中国东南部的大地构造演化提供了新的制约。地质、地球化学和年代学资料均表明扬子南缘的板溪群是一正常的元古代地层单位。华南一扬子晚元古代（晋宁期）碰撞造山运动导致了上述沉积岩的“Ｎｄ同位素漂移”。 相似文献
10.
本文论述了晋东南榆社一带的各期黄土。这里是黄土自西而东分布的过渡地带,黄土的性状有共性也有各自的特性。晋东南的黄土分为早更新世老Ｒ红土、早至中更新世新Ｒ红土、中更新世上离石黄土、晚更新世马兰黄土和全新世黄土。古地磁年代学测试和剖面观察获得的各期黄土年龄为：老Ｒ红土形成于２．５－１．５ＭａＢ．Ｐ,新Ｒ红士形成于０．９—０．６ＭａＢ．Ｐ,离石黄土形成于０．６—０．１ＭａＢ．Ｐ。它们彼此之间都有不整合面相隔。自Ｒ红土开始出现,就意味着榆社古湖开始消失,气候环境向半干旱－半湿润方向发展。但比黄土高原略为湿润,夏季风的影响更强些。 相似文献
11.
《地学前缘(英文版)》2020,11(4):1337-1344
The Quantougou(QTG) Fauna in central Lanzhou Basin is an important late Mid-Miocene fauna on the northeastern Tibetan Plateau margin,but its numerical age remains a matter of debate.Here,we present a new magnetostratigraphic record for a fluvio-lacustrine section to further constrain the age of the QTG Fauna.Results suggest that the studied section spans from polarity chrons C5Cn.2n to C5 n.2n or C5 An.1n,with ages of ca.16.5 Ma to 10 Ma or 16.5 Ma to 12 Ma.The QTG Fauna is located at the top of polarity chron C5r.3 r or C5 Ar.2 r,which corresponds to an age of 11.7 Ma or 12.8 Ma for the fauna.Accordingly,the associated Myocricetodontinae(a subfamily of Gerbillidae,Rodentia) is suggested to have appeared in the Lanzhou Basin at 11.7 Ma or 12.8 Ma,which is the oldest Myocricetodontinae in East Asia but is still much younger than the ～20 Ma appearance of this subfamily in West and South Asia.Our age data support the interpretation that East Asian Myocricetodontinae originated from South Asia.The QTG fauna further suggest a dry and open grassland environment,which is consistent with global cooling after the Mid-Miocene Climatic Optimum. 相似文献
12.
中国黄土磁性地层与生物地层对比 总被引：2，自引：0，他引：2
本文统计了中国黄土地层中发现的哺乳动物化石并对一些发现较丰富哺乳动物化石的黄土剖面进行了磁性地层学研究，分析了磁性地层与生物地层对比结果，讨论了黄土层中哺乳动物化石的时空分布，以及有关气候环境问题。 相似文献
13.
Timing of the Nihewan formation and faunas 总被引：2，自引：0，他引：2
Magnetostratigraphic dating of the fluvio-lacustrine sequence in the Nihewan Basin, North China, has permitted the precise timing of the basin infilling and associated Nihewan mammalian faunas. The combined evidence of new paleomagnetic findings from the Hongya and Huabaogou sections of the eastern Nihewan Basin and previously published magnetochronological data suggests that the Nihewan Formation records the tectono-sedimentary processes of the Plio-Pleistocene Nihewan Basin and that the Nihewan faunas can be placed between the Matuyama-Brunhes geomagnetic reversal and the onset of the Olduvai subchron (0.78-1.95 Ma). The onset and termination of the basin deposition occurred just prior to the Gauss-Matuyama geomagnetic reversal and during the period from the last interglaciation to the late last glaciation, respectively, suggesting that the Nihewan Formation is of Late Pliocene to late Pleistocene age. The Nihewan faunas, comprising a series of mammalian faunas (such as Maliang, Donggutuo, Xiaochangliang, Banshan, Majuangou, Huabaogou, Xiashagou, Danangou and Dongyaozitou), are suggested to span a time range of about 0.8-2.0 Ma. The combination of our new and previously published magnetostratigraphy has significantly refined the chronology of the terrestrial Nihewan Formation and faunas. 相似文献
14.
The Cuddapah Basin is one of many Proterozoic, intracontinental sedimentary basins across Peninsular India. The basin comprises several unconformity-bounded successions, the lowermost of which (the Papaghni Group and overlying Chitravati Group) are intruded by dolerite sills that contact metamorphosed their host rocks. A mafic-ultramafic sill from the base of the Tadpatri Formation in the Chitravati Group was previously dated at c. 1885 Ma, and interpreted to be part of a large igneous province (LIP). We have dated two samples of a felsic tuff from the upper part of the Tadpatri Formation at 1864 ± 13 Ma and 1858 ± 16 Ma; combining data from the two samples yields a weighted mean date of 1862 ± 9 Ma. Mafic sills intrude rocks stratigraphically above the tuffaceous beds, indicating that mafic magmatism continued until after c. 1860 Ma. Given that the sills intruded lithified rocks, some of the sills may be considerably younger than 1860 Ma. Mafic volcanic rocks are also known from below the unconformity at the base of the Chitravati Group, within the basal Papaghni Group (> c. 1890 Ma). Collectively, these data indicate that mafic sill emplacement spanned more than 30 myr so that it is likely to have been a protracted event or a series of events, and, therefore unlikely to represent a LIP. The time span for mafic magmatism is more compatible with episodic, lithospheric extension (passive rifting) during basin evolution than it is with a mantle plume (active rifting). 相似文献
15.
类Ｇａｌｏｗａｙｉｎｅｌａ长期以来被当作长兴阶的带化石，是长兴阶底界的标志。江西上高七宝山剖面表明Ｇａｌｏｗａｙｉｎｅｌａ富集层并非像以往认为的那样是稳定的一层，在此剖面上至少有二层：下层在Ｃｌａｒｋｉｎａｌｅｖｅｎｉ带之下，其上下均有典型的吴家坪期的菊石（Ｋｏｎｇｌｉｎｇｉｔｅｓ等）；上层与吴家坪期的牙形刺Ｃｌａｒｋｉｎａｏｒｉｅｎｔａｌｉｓ，Ｃ．ｇｕａｎｇｙｕａｎｅｎｓｉｓ，Ｃ．ｄｅｍｉｃｏｒｎｉｓ，Ｃ．ｌｉａｎｇｓｈａｎｅｎｓｉｓ共存。这一事实表明Ｇａｌｏｗａｙｉｎｅｌａｍｅｉｔｉｅｎｅｎｓｉｓ是吴家坪期的而不是长兴期的。为此建议，长兴阶的底界不用类定义，而以牙形刺Ｃｌａｒｋｉｎａｓｕｂｃａｒｉｎａｔａ和／或Ｃ．ｗａｎｇｉ的首次出现为准。 相似文献
16.
河北阳原台儿沟剖面泥河湾组底界的确定 总被引：7，自引：0，他引：7
河北阳原化稍营郝家台台儿沟剖面是泥河湾盆地新建的建阶剖面。剖面总厚度为151.45m,顶部的年龄约0.019Ma,深33.55m处为B/M界线,深123m处为M/G界线,剖面底的年龄约3.3Ma。划分为马兰组、郝家台组、泥河湾组和蔚县组。深45.65-122.65m间归泥河湾组,厚77m,泥河湾组以黄色调砂、粉砂、黏土质粉砂为主,中夹有灰绿色黏土,属河湖相沉积环境。泥河湾组底界确定的标志:底部出露较厚的砂层,代表一个沉积旋回的开始,与下伏湖沼相蔚县组呈整合接触;底界接近M/G界线,在M/G界线之上0.35m处;底界之下挖掘到早于2.6Ma的游河模拟鼠-副丁氏鼢鼠小哺乳动物化石组合和瓣鳃类化石。泥河湾组底界确定为2.6Ma。 相似文献
17.
《Journal of Asian Earth Sciences》2011,40(6):516-526
The Satpura Mountain Belt (also referred as Central Indian Tectonic Zone in recent literature) forms an important morphotectonic unit in the central part of India. Some of the recent workers have reported an orogenic event at ∼1000–900 Ma (termed “Sausar orogeny”) which led to amalgamation of the North Indian Block and the South Indian Block and formation of the Satpura Mountain Belt. In this model the stratigraphic relations of two important lithostratigraphic units on either side of the Satpura Mountain Belt (the Sausar Group in the south and the Vindhyan Supergroup on the north) are suggested to be revised from previously held ideas. Critical analyses of available published work in the region to assess the status of the Sausar Group vis a vis the Vindhyan Supergroup was carried out. It is found that the ideas proposed by the recent workers stem from an earlier interpretation that the Sausar Group has monocyclic evolution and the earliest fabric in the Sausar Group is marked by a schistosity with EW strike. Re-mapping of the gneissic rocks and adjacent matasedimentary rocks of Khawasa, Deolapar, and Kandri–Mansar areas revealed presence of gneissic rocks and granulites of two generations, and of four phases of superposed deformations in the metasediments and gneisses. The older gneisses and granulites constitute the basement over which the rocks of the Sausar Group were deposited; and the younger gneisses developed by metamorphism and migmatisation of the rocks of the Sausar Group. The latter types are found in the Khawasa–Ramakona areas. Contrary to the belief of the recent workers that no volcanic activity is present in the Sausar Group, volcanic rocks marked by amygdular basic flows and tuffs have been mapped from different parts of the Sausar Group. Migmatisation and metamorphism of these volcanic rocks (of the Sausar Group) have given rise to amphibolites and granulites in Khawasa and Ramakona areas. Therefore, the use of fabric patterns in these areas to suggest that the granulite facies metamorphism in the Ramakona–Katangi granulite domain was pre-Sausar in age is debatable.Available geochronological data of the Satpura Mountain Belt and its eastward continuation into the Chhotanagpur Gneiss terrain indicate that the basement and cover rocks of these areas were subjected to multiple deformation and metamorphic episodes of similar style and nature. The earliest deformation and metamorphism of the rocks of the Sausar Group and its equivalent rocks to the east took place at ∼2100–1900 Ma. The regional EW trend of the belt developed during the second deformation at ∼1800–1700 Ma and again at ∼1600–1500 Ma. This deformation was accompanied by migmatisation and granulite facies metamorphism in the northern domain of the Sausar Belt and in the Chhotanagpur Gneiss region. Late phase low intensity deformations in the region were associated with thermal events at ∼1100–1000 Ma and ∼900–800 Ma.The ∼EW trending fabric, referred as “Satpura orogenic trend” in Indian literature marks a major compressional tectonic event, developed during the second deformation of the Sausar Group. This has its counter part in Western Australia as the Capricorn orogeny (∼1780–1830 Ma). The development of the Satpura Mountain Belt during the Grenvillian orogeny is ruled out from the synthesis of event stratigraphic data of the region and from its comparison with the Western Australian Craton. 相似文献
18.
B. S. Mackness P. W. Whitehead G. C. McNamara 《Australian Journal of Earth Sciences》2013,60(4):807-811
A new radiometric date of 3.6 Ma for the basalt overlying fossiliferous units of the Allingham Formation, provides a minimum age for the Bluff Downs Local Fauna. Ground studies and interpretation of aerial photography has clarified the volcanic history of the area and a new basalt flow has been identified and named. Although the age of the capping basalt permits a younger age for the Bluff Downs Local Fauna than originally described, the stratigraphy, combined with the interpreted stage of evolution of the fauna, still supports an Early Pliocene age for the site. 相似文献