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1.
LI Wei WAN Xiaoqiao Atsushi MATSUOKA ZHANG Shuqin QU Haiying Tsubasa TAMURA Kohei YOSHINO 《《地质学报》英文版》2015,89(1):285-299
Defining the Jurassic-Cretaceous boundary is a controversy in stratigraphic study of the world. It has been widely accepted that this boundary can be defined at the bottom of Berriasian in Tethys, with the appearance of the ammonite Berriasella jacobi dating to ca. 145 Ma. However, it is difficult for the widespread terrestrial deposits in China to correlate with the international standard of marine facies. The Somanakamura Group in Japan is represented by a succession of marine-continental transitional strata. It provides a bridge of marine and nonmarine stratigraphic correlation. The ammonite and radiolarian fossils preserved in this group suggest an age from Bajocian to early Valanginian. The J-K boundary was defined in or atop the Tomizawa Formation of the group according to the ammonite data. The present authors study the fossil spores and pollen newly found from the Tomizawa and Koyamada formations. Three assemblages have been recognized. They are Assemblage 1 (Cyathidites-Classopollis) from the upper part of the Tomizawa Formation, Assemblage 2 (Cyathidites-Jiaohepollis) from the lower part of the Koyamada Formation, and Assemblage 3 (Cyathidites-Spheripollenites-Ephedripites) from the middle to upper part of the Koyamada Formation. With the reference of ammonite evidence, the J-K boundary can be defined between Assemblage 1 and Assemblage 2. This palynological J-K boundary can be correlated with that of terrestrial sequence in China. However, local biostratigraphy imply that the continental J-K boundary in China is of 135 or 137 Ma age. It has a considerable discrepancy from the marine standard. Biogeographically, the distribution pattern of spores and pollen in southern China is in accordance with that in the Somanakamura Group, which parallels the Tuchengzi Formation in northeastern China. By the palynological correlation between the Somanakamura Group and the strata in southern China, and then with the sequence in northeastern China, it is suggested that the continental J-K boundary is located in the Tuchengzi Formation. 相似文献
2.
It has been the habit of most geologists to speak of an earth-movement in some special regional term which, as a rule, primarily refers to the trend of the resulting flexures or fractures and eventually to the time when the moverment took place. This dual implication of a tectonic term is largely to be 相似文献
3.
LIU Jianni HAN Jian LI Jinshu WU Yichen PENG Jie QI Nan YANG Yiyao LI Juan 《《地质学报》英文版》2016,90(6):1939-1945
The Guanshan Biota from the Cambrian Stage 4 Wulongqing Formation is a typical Burgess-shale type Lagerst?tte that had witnessed the Cambrian explosion. Here we report two new localities of the Guanshan Biota, which is located at Baimei village, south of Kunming and Xinglong village, Wuding County, Yunnan Province respectively. Both localities produce soft-body fossils and several new taxa, e.g. a new species of palaeoscolecidans (Palaeoscolex xinglongensis sp. nov.) reported herein. The comparative study of the new species with similar form not only indicates that there is a diversification of palaeoscolecid species in Guanshan Biota, but also strengthens the ties between the older Chengjiang Biota and the younger Kaili Biota (and also the coeval Burgess Shale community). Three paleoecological features, including high diversity, little disparity and richness of palaeoscolecid worms, are summarized as a case study to represent the differences between Guanshan and Chengjiang Biota. 相似文献
4.
The map expression of "abrupt" changes in lateral stratigraphic level of a thrust fault has been traditionally interpreted to be a result of the presence of(1) a lateral(or oblique) thrust-ramp,or(2) a frontal ramp with displacement gradient、and/or(3) a combination of these geometries.These geometries have been used to interpret the structures near transverse /ones in fold-thrust belts(FTB).This contribution outlines an alternative explanation that can result in the same map pattern by lateral variations in stratigraphy along the strike of a low angle thrust fault.We describe the natural example of the Leamington transverse zone.which marks the southern margin of the Pennsy lvanian—Permian Oquirrh basin with genetically related lateral stratigraphic variations in the North American Sevier(TB.Thus.the observed map pattern at this zone is closely related to lateral stratigraphic variations along the strike of a horizontal fault.Even though the present-day erosional level shows the map pattern that could be interpreted as a lateral ramp.the observed structures along the Leamington zone most likely share the effects of the presence of a lateral(or oblique) ramp,lateral stratigraphic variations along the fault trace.and the displacement gradient. 相似文献
5.
The Rhinocerotidae is one of the most common and important families in the Pleistocene mammalian fauna of South China. Since the last century, most of the Pleistocene rhinocerotid fossils were prematurely assigned to Rhinoceros sinensis, which has resulted in confusion of taxonomy for decades, especially in South China. The Yanjinggou area in Chongqing Municipality of China, where the neotype of R. sinensis came from, has yielded abundant rhinocerotid fossils and is a key area to solve this problem. A recently discovered juvenile skull from a karstic fissure in this area can be referred to Dicerorhinus sumatrensis (Fischer, 1814), which is the first confirmed non-Rhinoceros rhinocerotid from the area. This new finding indicates that non-Rhinoceros fossils might have been mixed in AMNH collection from Yanjinggou and thus the diagnosis of Rhinoceros sinensis needs reformation. On the other hand, Stephanorhinus ?kirchbergensis is also detected in Granger’s collection based on our reobservation. The coexistence of Rhinoceros, Dicerorhinus and Stephanorhinus shows the higher diversity of Pleistocene rhinocerotids in South China. 相似文献
6.
The Cenozoic volcanostratigraphy in the Changbaishan area had complex building processes. Twenty-two eruption periods have been determined from the Wangtian’e, Touxi, and Changbaishan volcanoes. The complex volcanostratigraphy of the Changbaishan area can be divided into four types of filling patterns from bottom to top. They are lava flows filling in valleys (LFFV), lava flows filling in platform (LFFP), lava flows formed the cone (LFFC), and pyroclastic Flow filling in crater or valleys (PFFC/V). LFFV has been divided into four layers and terminates as a lateral overlap. The topography of LFFV, which is controlled by the landform, is lens shaped with a wide flat top and narrow bottom. LFFP has been divided into three layers and terminates as a lateral downlap. The topography of LFFP is sheet and tabular shaped with a narrow top and wide bottom. It has large width to thickness ratio. It was built by multiple eruptive centers distributed along the fissure. The topography of LFFC, which is located above the LFFP, has a hummocky shape with a narrow sloping top and a wide flat bottom. It terminates as a later downlap or backstepping. It has large width to thickness ratio. It was built by a single eruptive center. The topography of PFFC/V, which located above the LFFC, LFFP, or valley, has the shape of fan and terminates as a lateral downlap or overlap. It has a small width to thickness ratio and was built by a single eruptive center. The filling pattern is controlled by temperature, SiO2 content, volatile content, magma volume, and the paleolandform. In the short term, the eruptive production of the Changbaishan area is comenditic ash or pumice of a Plinian type eruption. The eruptive volume in future should be smaller than that of the Baguamiao?period, and the filling pattern should be PFFC/V, which may cause huge damage to adjacent areas. 相似文献
7.
Microorganisms Linked to Neoproterozoic Microspar Carbonate Sedimentation in the Jilin-Liaoning Area 总被引：2，自引：1，他引：2
GE Ming KUANG Hongwei MENG Xianghua George FURNISS Institute of Sedimentary Basin China University of Geoscience Xueyuan Ro Beijing China Yangzi University Nanjing Jiangsu China Geology Department University of Montan Missoul Montan USA 《《地质学报》英文版》2004,78(3):784-789
Molar-tooth carbonate refers to a sort of rock that has ptygmatical folded structure comparable to the ivory. This kind of carbonate exists in a special time range (from Middle to Neoproterozoic). Its origin and the possibility to use it in stratigraphic correlation of the paleocontinent is the key task of the IGCP447, a project on Proterozoic molar tooth carbonates and the evolution of the earth (2001-2005). The importance lies in that the molar-tooth structure is the key to solving problems related to Precambrian biological and global geochemical events. The molar-tooth structure is associated with microorganisms. Development and recession of such carbonates have relations with the evolution process of early lives and abrupt changes in sea carbonate geochemistry. In recent years, based on researches on petrology, geochemistry and Sr isotope of molar-tooth carbonate in the Jilin-Liaoning and Xuzhou-Huaiyang area, the authors hold that it can be used as a marker for stratigraphic sequence and sedimentary 相似文献
8.
The use of the heavy minerals in sedimentary rocks as a means for correlation of stratigraphic problem is becoming more and more widespread in recent years, especially in England and United States. Where the rock formations are scanty in fossils or can not be correlated by fossils alone, the study 相似文献
9.
LI Guobiao 《《地质学报》英文版》2007,(6)
As one of the mélanges in the southern side of the Yarlung-Zangbo suture zone,the Saiqu mélange in southern Tibet is important for understanding the evolution of the Neo-Tethys ocean.The age of the Saiqu mélange,however,has been debated due to the lack of reliable fossil evidence in matrix strata.Based on lithological similarities with platform strata in southern Tibet and limited fossils from exotic blocks,previous studies variously ascribed the Saiqu mélange to be Triassic in general,Late Triassic,or Late Cretaceous.Here we reported planktonic foraminiferal faunas from the matrix strata of the Saiqu mélange.The new fossils yield a Late Cretaceous age,which is so far the best age constraint for the mélange.Regional stratigraphic correlation indicates that the Cretaceous Oceanic Red Beds (CORBs)in Saiqu may be time equivalent to the CORBs of the Zongzhuo Formation in neighboring regions.Thus the Saiqu mélange should be correlated to the Upper Cretaceous Zongzhuo Formation rather than the Triassic Xiukang Group,as previously suggested. 相似文献
10.
The stratigraphic division and sequence of the Upper Cretaceous sediments in eastern Heilongjiang Province,China,have been ambiguous and controversial,mainly due to a lack of biostratigraphically useful fossils and related radiometric dating.A new species of angiospermous fossil plant.Platanus heilongjiangensis sp.nov.,from Qitaihe in eastern Heilongjiang has been found in sediments conformably above which zircons from a rhyolitic tuff has been dated by U-Pb radiometric methods as 96.2± 1.7 Ma.indicating that the Upper Houshigou Formation is of Cenomanian age.This discovery not only provides new data to improve our stratigraphic understanding of the Houshigou Formation,but also shows that Platanus flourished in the early Late Cretaceous floras of the region.This new study also indicates active volcanism taking place in the eastern Heilongjiang region during the Cenomanian of the Late Cretaceous. 相似文献
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澄江生物群、凯里生物群、加拿大布尔吉斯生物群和西伯利亚藻群中均有丰富的藻类化石。根据前寒武纪宏观藻类的分布以及凯里生物群和布尔吉斯页岩生物群中藻类和后生动物的相似性，讨论了前寒武纪至中寒武世期间生物地理分区的控制因素。对几个生物群中的藻类化石和后生动物化石的对比研究发现,在相近的纬度范围内, 动植物化石组合特征非常相似; 而纬度明显差异时, 藻类生物群及后生动物群也具有明显的差异。由于后生生物在前寒武纪至中寒武世期间具有低的演化程度和分异能力，因此生物地理分布的主要控制因素是古纬度。而Schopf (1976)的生物地理分区模式不适合这一时期的生物地理分区。结合前寒武纪至中寒武世后生生物化石的分布情况，建立了前寒武纪-中寒武世时期的生物地理分区模式。这个模式较好地解释了分布在北美大陆和华南大陆上的寒武纪生物群相似的原因。 相似文献
13.
The Ediacaran Period takes its name from the fossils of the Ediacara biota, which represent the first appearance of large and diverse assemblages of organisms in the fossil record. Although the global record of these distinctive body fossils is now well known, a previously unrecognized megascopic organic record of textured organic surfaces (TOS) occurs in the Ediacara biota. However, TOS is also a feature over a wider range of paleoenvironmental settings, where body fossils are unknown, in Ediacaran siliciclastic successions that have been studied in Australia, Namibia and western North America.Paleoecological analysis of successive bedding planes of strata from the late Ediacaran Rawnsley Quartzite in the Flinders Ranges of South Australia, reveals that TOS represent the most common organic features in bedding-surface assemblages of the Ediacara biota. The TOS consist of preserved, patterned assemblages of textured organic mats, fibers and simple tubular body fossils. Complex Ediacara body fossils while striking for their distinctive body plans, and dominating some of the beds, are relatively minor components of combined overall surface area. Many elements of TOS have previously been miss-diagnosed as trace fossils, which are in practice limited to two or at most three morphotypes that indicate the presence of Bilateria. Although TOS represent a simpler grade of organismic construction than discrete and more complex Ediacara body fossils, they were preserved in a similar manner. Marked variability in all components of the biota between successive surfaces suggests that Ediacara ecologies fluctuated at short intervals despite an apparently consistent sedimentary regime. 相似文献
14.
贵州瓮安埃迪卡拉（震旦）纪陡山沱期磷酸盐化生物群具有生物多样性特征，包含有蓝菌、多细胞藻类、疑源类、后生动物休眠卵及胚胎、可疑的海绵动物、管状后生动物和微小两侧对称的后生动物等化石类型，是迄今为止全球保存最为完好的晚前寒武纪磷质化石库。瓮安陡山沱组磷质岩提供了早期生命从简单到复杂进化过程中的重要化石记录，展示了埃迪卡拉生物群出现以前早期多细胞生物的生命景观，为研究晚前寒武纪生物圈面貌提供了一个重要的埋葬学窗口。近来，通过醋酸浸解法，在贵州瓮安陡山沱期含磷地层中发现了大量疑似后生动物的实体化石（包含了所有已经报道的类型或与之相似的化石类型）新材料，为了解这些化石的内部构造特征，将一些化石包埋后制作了定向薄片。基于上述化石新材料，结合定向薄片的研究和前人的研究成果，本文详细介绍了瓮安生物群中后生动物化石研究的新进展和存在的问题。 相似文献
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Joseph G. Meert Anatoly S. Gibsher Natalia M. Levashova Warren C. Grice George D. Kamenov Alexander B. Ryabinin 《Gondwana Research》2011,19(4):867-880
The Cambrian explosion, c. 530–515 Ma heralded the arrival of a diverse assembly of multicellular life including the first hard-shelled organisms. Fossils found in Cambrian strata represent the ancestors of most modern animal phyla. In contrast to the apparent explosiveness seen in the Cambrian fossil record, studies of molecular biology hint that the diversification observed in Cambrian strata was rooted in ancestry extending back into the Ediacaran (635–542 Ma). Fossil evidence for this mostly cryptic phase of evolution is derived from the soft-bodied fossils of the Ediacaran biota found throughout the world and bilaterian embryos found in the Doushantuo lagerstätte in South China. The first appearance of Ediacara fauna is thought to have followed the last of the ~ 750–635 Ma Neoproterozoic glacial episodes by 20–30 million years. In this paper, we present evidence for the oldest discovery of the ‘Ediacara’ discoidal fossils Nimbia occlusa and Aspidella terranovica (?) that predate the early Cryogenian glaciations by more than fifty million years. There is considerable disagreement over the significance of discoidal Ediacaran fossils, but our findings may support earlier suggestions that metazoan life has roots extending deeper into the Proterozoic Eon. We also confirm the presence of a Late Cryogenian (e.g. “Marinoan”) glaciation on the Lesser Karatau microcontinent including dropstones and striated clasts within the glacial strata. 相似文献
17.
湘西震旦纪武陵山生物群的化石形态学特征和归属 总被引：2，自引：0，他引：2
湘西桃源理公港震旦系留茶坡组中部黑色页岩中的炭质压膜化石,为研究末前寒武纪晚期生物学提供了一个稀有的布吉斯页岩型分类学窗口。根据已知属种和新获材料的研究,确定了17个明显的形态类型,讨论了每种形态类型特征及其可能的生物学属性,指出除个别化石可能为两侧对称动物外,其余绝大多数化石可以解释为原核生物或多细胞藻类,系统发育上与绿藻、褐藻、蓝藻细菌等相关。具固着器、叶状体为球状或具同心纹构造的Apsidiumsphaericus的发现,进一步证明典型埃迪卡拉动物群(或白海生物群)中简单的圆盘状化石可能为多细胞藻类,而不是水母。武陵山生物群中具同心纹结构的大型圆盘状化石的出现及其共生生物特点,指示该生物群是埃迪卡拉期生物分异发展阶段的产物,是末前寒武纪晚期一个以多细胞藻类发育为特色的新型生物群。 相似文献
18.
Leaf‐shaped Ediacaran fronds are among the most widespread and readily recognized members of the terminal Neoproterozoic Ediacara Biota. Ediacaran fronds gathered nutrients from the water column through filter feeding or direct nutrient absorption, resulting in the onset of modern‐style ecological competition complete with denizens occupying distinct tiers in the water column. It is believed that the frond shape most likely represents a common need to elevate a feeding apparatus higher in the water‐column to feed from the upper (> 20 cm) tiers. Therefore, the frond shape represents a shared ecology, not ancestry. 相似文献
19.
Grant M.Young 《地学前缘(英文版)》2015,6(4)
The second half of the Ediacaran period began with a large impact e the Acraman impact in South Australia, which was accompanied by a negative d13Ccarb anomaly and an extinction-radiation event involvi... 相似文献
20.
Marc Laflamme Simon A.F. Darroch Sarah M. Tweedt Kevin J. Peterson Douglas H. Erwin 《Gondwana Research》2013,23(2):558-573
The Ediacaran–Cambrian transition signals a drastic change in both diversity and ecosystem construction. The Ediacara biota (consisting of various metazoan stem lineages in addition to extinct eukaryotic clades) disappears, and is replaced by more familiar Cambrian and Paleozoic metazoan groups. Although metazoans are present in the Ediacaran, their ecological contribution is dwarfed by Ediacaran-type clades of uncertain phylogenetic affinities, while Ediacaran-type morphologies are virtually non-existent in younger assemblages. Three alternative hypotheses have been advanced to explain this dramatic change at, or near, the Ediacaran–Cambrian boundary: 1) mass extinction of most Ediacaran forms; 2) biotic replacement, with early Cambrian organisms eliminating Ediacaran forms; and 3) a Cheshire Cat model, with Ediacaran forms gradually disappearing from the fossil record (but not necessarily going extinct) as a result of the elimination of unique preservational settings, primarily microbial matgrounds, that dominated the Ediacaran. To evaluate these proposed explanations for the biotic changes observed at the Ediacaran–Cambrian transition, environmental drivers leading to global mass extinction are compared to biological factors such as predation and ecosystem engineering. We explore temporal and biogeographic distributions of Ediacaran taxa combined with evaluations of functional guild ranges throughout the Ediacaran. The paucity of temporally-resolved localities with diverse Ediacaran assemblages, combined with difficulties associated with differences in taphonomic regimes before, during, and after the transition hinders this evaluation. Nonetheless, the demonstration of geographic and niche range changes offers a novel means of assessing the downfall of Ediacara-type taxa at the hands of emerging metazoans, which we hypothesize to be most likely due to the indirect ecological impact metazoans had upon the Ediacarans. Ultimately, the combination of studies on ecosystem construction, biostratigraphy, and biogeography showcases the magnitude of the transition at the Ediacaran–Cambrian boundary. 相似文献