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1.
Sections from the eastern margin of the Siberian Platform provide important reference sections for stable isotopic correlation of the newly defined Precambrian–Cambrian boundary level since they contain some of the earliest pre-Tommotian shelly fossil assemblages known, and are amenable to δ13C stratigraphy. Stable isotopes are examined from the Dvortsy and Ulakhan–Sulugur sections (River Aldan), where sparse pre-Tommotian assemblages occur, and from the Uchur River region, where the putative Anabarites trisulcatus and Purella antiqua Zones of the Nemakit–Daldynian Stage are well-developed. Diagenetic resetting of δ18O and δ13C must be taken into account when comparing such sections. Simple corrections allow for stable isotopic correlation of basal Nemakit–Daldynian and Tommotian strata across eastern Siberia. 相似文献
2.
《Gondwana Research》2014,25(3):1139-1152
In the earliest Cambrian the major diversification of small shelly fossils (SSFs) was the first episode of the so-called Cambrian Explosion. In order to clarify the background environmental conditions of this event, we examined the lowermost Cambrian strata with bedded phosphorites in the Chengjiang area, South China. The lowermost Cambrian (the Zhongyicun Mb of the Zhujiaqing Fm) in eastern Yunnan is composed of bedded phosphorites and phosphatic limestones with diverse SSFs. We investigated 3 sections within the Chengjiang area at Hongjiachong, Maotianshan, and Xiaolantian. Detailed lithostratigraphic analysis of outcrops and drill cores at Hongjiachong indicates that the Zhongyicun Mb consists of 5 distinct units, A to E in ascending order. The presence of 15 genera of SSFs in 20 horizons shows that the Zhongyicun Mb yields two distinct SSF assemblages of Fortunian age (earliest Cambrian; 541–529 Ma); i.e. the first assemblage with simple-shape SSFs (Anabarites, Protohertzina) from basal Unit A, and the second assemblage with various molluscan shells (Paracarinachites, Ocruranus–Eohalobia) from Units C–E. As well as abundant phosphate grains, all SSFs occur as clastic grains, suggesting that phosphorite was primarily formed in extreme shallow-water settings, as were the small shelly animals. We established that the first occurrence of the second SSF assemblage is at least 5 m lower (ca. 1–2 myr earlier in age) than previously reported in Chengjiang, and we speculate that the major diversification in SSF assemblage likely occurred during the Fortunian, at least before ca. 534 Ma. Judging from the rift-related tectonic setting and relevant paleogeography of western South China, we further speculate that the Zhongyicun Mb was primarily deposited in restricted embayments in the Kangdian rift basin, and that the rapid SSF diversification in the Fortunian occurred in a unique setting in highly phosphorus-rich seawater. 相似文献
3.
A New Species of Septuconularia (Hexangulaconulariidae, Cnidaria) from Cambrian Stage 2, South China
SONG Zuchen GUO Junfeng HAN Jian Heyo VAN ITEN QIANG Yaqin PENG Jiaxin SUN Jie ZHANG Zhifei 《《地质学报》英文版》2022,96(3):757-765
Hexangulaconulariids, an extinct family of medusozoan small shelly fossils (SSFs), were a conspicuous component of early Cambrian, shallow marine platform communities in South China. Described herein is Septuconularia crassiformis sp. nov. from Bed 5 of the Yanjiahe Formation (Cambrian Stage 2) in the Three Gorges area of Hubei Province. The new species differs from the type and only other known species, S. yanjiaheensis, in the shape of the abapical portion and in the degree of curvature of the adapertural margin. The anatomy of the apical portion of the new species is unknown. The diagnosis of the genus Septuconularia is emended and the spatio-temporal distribution of hexangulaconulariids in South China is summarized. Finally, S. yanjiaheensis, with its slit-like aperture and very narrow transverse cross-section, may have been better adapted to the shallow platform environment than the broader S. crassiformis, which appears to have been less common than the type species. 相似文献
4.
《Gondwana Research》2016,29(4):1543-1565
Early Cambrian small skeletal fossils (SSFs) are studied and revised from the Zhenba–Fangxian Block of the transitional zone between the Yangtze Block and the South Qinling Terrane. The study reveals a diverse fauna with 47 species of various biological affinities, including the new species Gapparodus gapparites sp. nov. The SSFs are assigned to the newly defined Cambroclavus fangxianensis–Rhombocorniculum cancellatum Assemblage Zone. Based on the investigated SSF fauna from Zhenba County, Southeast Shaanxi of China and published data, a palaeobiogeographic study is carried out for the Cambrian Stage 3 (equivalent to the Atdabanian–Botoman of Siberia). A hierarchical Pearson similarity cluster analysis of 295 species from 32 regions of the world indicates a distinct palaeobiogeographic pattern with seven faunal provinces. The result is mostly consistent with existing palaeogeographic reconstructions for the early Cambrian. However, it is also shown that the SSF assemblages of the Zhenba–Fangxian Block have low similarity with those of the Yangtze Block. Instead, they share high similarity with those from Armorica, Tarim and the Karatau–Naryn terranes (South Kazakhstan/North Kyrgyzstan). The Yangtze Block has a unique SSF assemblage dissimilar to most of other regions. The Terreneuvian–Cambrian Stage 3 sedimentary sequence of the Zhenba–Fangxian Block is more consistent with that of the South Qinling Terrane. Besides, sedimentary Ediacaran manganese ore deposits and Cambrian barite/witherite deposits have unique distribution pattern on the Zhenba–Fangxian Block. Derived from the profound dissimilarities in faunal composition, sedimentary sequence and distribution of sedimentary ore deposits, we hypothesize that during the Neoproterozoic–Cambrian transition, the Zhenba–Fangxian Block might have been an independent terrane and more distant from the Yangtze Block. The palaeobiogeographic analysis of SSFs also indicates a closer alliance between Avalonia and Siberia. It corroborates the palaeogeographic reconstruction of North China at the margin of Gondwana, in the vicinity of Australia, Antarctica, and Armorica. 相似文献
5.
GUO Junfeng LI Yong HAN Jian ZHANG Xingliang ZHANG Zhifei OU Qiang LIU Jianni SHU Degan Shigenori MARUYAMA Tsuyoshi KOMIYA 《《地质学报》英文版》2008,82(6):1124-1132
Apart from previously reported Small Shelly Fossils (SSFs), a macroscopic fossil assemblage, comprising abundant algae, cone-shaped tubular fossil forms, and probable impressions of a megascopic metazoan, comes from the Lower Cambrian Yanjiahe Formation in the Yangtze Gorges area of western Hubei Province, south China. The visible fossils are preserved in thin-laminated siltstone or muddy siltstone intercalated between 8–15 mm-thick carbonate deposits, probably representing sedimentary settings of a constrained local depression in the shallow water carbonate platform during the Early Cambrian Meishucunian Stage. The macroscopic fossil association provides significant fossil evidence about the evolution of life from the late Precambrian to the ‘Cambrian explosion’ interval. 相似文献
6.
QIU Hao FENG Lianjun CHU Xuelei LI Luoyang ZHANG Xingliang LI Jinhua 《《地质学报》英文版》2022,96(4):1294-1307
Silica-phosphatic nodules are abundant in black shales of the Yanjiahe Formation in the Three Gorges Area of South China, which is correlated to the Fortunian Stage, Terreneuvian Series, Cambrian System. The nodules are rich in small shelly fossils and hence attract the attention of numerous paleontologists and sedimentary geologists. However, the genesis of the nodules and the preservation of the small shelly fossils are poorly understood. Here we analyze morphological, structural, mineralogical and chemical features of the nodules in multiscale using a combination of micro-X-ray fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy and confocal laser Raman spectroscopy. Results reveal that nodules are concentric in chemical and mineralogical compositions, comprising a silica-phosphatic core encrusted sequentially by a phosphatic zone, a siliceous zone and a very thin pyrite outer rim. The black shales hosting the nodules demonstrate a laminated texture of alternating clayey and silty laminae, which were respectively deposited in sulfidic/less sulfidic, high/low production, intense/weak chemical weathering conditions. The phosphogenesis of the nodules resulted in the phosphatization of small shelly fossils, which prevented the fossils from being dissolved during diagenesis, whereas the silica encrustation sealed the fossils within the nodules and thus protected the fossils from alteration by deep burial and surface weathering. 相似文献
7.
早寒武世梅树村期小壳化石处于＂寒武纪生命大爆发＂的第一幕,对于揭示后生动物起源至关重要。对陕南宽川铺地区早寒武世早期宽川铺组第一个小壳化石组合带中发现的动物球状胚胎化石进行大量观察,发现了两枚Olivooides-like的新型动物胚胎化石。此类化石的胚胎表面并非Punctatus Emeiensis常见的密集分布的典型或非典型的尖刺状结构,而是呈基端具螺旋状环褶、末端较圆滑的锥状突起。新型动物卵的发现暗示了早寒武世梅树村期动物化石卵的多样性很可能发端于新元古代埃迪卡拉纪。 相似文献
8.
埃迪卡拉纪—寒武纪转换时期小壳化石的突然出现是世人瞩目的重要演化事件之一,它见证了动物的爆发式快速演化过程,标志着以两侧对称动物为特征的寒武纪生态系统的开始。湖北三峡地区寒武系纽芬兰统岩家河组处于幸运阶—第二阶这一关键层段,是研究上述问题的理想地区之一。岩家河组小壳化石研究最近取得的进展,为寒武系纽芬兰统幸运阶/第二阶界线的标定,和寒武纪早期软体动物和刺胞动物的演化及个体发育提供了重要的化石依据,本文对其进行了总结。全球界线层型剖面和点位(GSSP)寒武系第二阶底界划分标志的Watsonella crosbyi和Aldanella attleborensis在岩家河组第5段底部的同时出现,意味着岩家河组第5段已归属寒武系第二阶。这两类软体动物化石均广泛分布于华南、蒙古、西伯利亚和北美等大陆碳酸盐岩相寒武系第二阶地层中,它们均是定义寒武系第二阶底界的有力竞争者。另外,W.crosbyi壳顶下方一对肌肉附着结构的发现提供了重要的软组织结构信息,证实了W.crosbyi为内腹型壳,归属为未扭曲的软体动物太阳女神螺类。新发现六方锥石类Septuconularia yanjiaheensis具侧向压扁、两辐射对称的、14个等大锥面的围鞘,是迄今所描述的六方锥石类中锥面数最多的类型。根据横肋疏密程度,围鞘由下向上可分为三部分,可能代表胚胎期、幼年期和成年期不同的生长阶段。Septuconularia显然由寒武系幸运阶Hexaconularia通过扇面扩增演变而来,证明Hexaconularia可能是Arthrochites和Septuconularia之间的中间过渡类型。新发现的橄榄蛋类Octapyrgites elongatus与幸运阶Olivooides和Quadrapyrgites十分相似,围鞘由方形的壳顶区和波纹状倒宝塔形的远顶区组成。然而Octapyrgites只有8个口折叶,有别于具12个口折叶的Quadrapyrgites。通过与幸运期水母类多种对称方式对比,发现在寒武系第二阶橄榄蛋类数量减少和五辐射对称骨状壳类缺失,表明在幸运期/第二期转换时期,底栖固着型的刺胞动物水母类多样性发生了明显衰落,甚至部分绝灭,而同期的两侧对称动物则迅速辐射演化。 相似文献
9.
The upper Qigeblaq Formation （Fm） dolostones and the Yurtus Fm phosphatic cherts, black shales, limestones, and dolostones are widely distributed in the Precambrian/Cambrian transitional succession of the Aksu-Wushi area. Negative δ13C excursion above the Yurtus Fm/ Qigeblaq Fm boundary was determined in this study. The pronounced negative carbon isotope excursion occurs in the phosphatic chert layers at the bottom of the Cambrian Yurtus Fm, below which the first appearance of the Asteridium- Heh＇osphaeridium-Comasphaeridium （AHC） acritarch assemblage zone. The δ13C curve of the lower part of the Yurtus Fm in the Aksu-Wushi area was found to be correlated with the early Cambrian δ13C curves of the Zhujiaqing Fm （Daibu Member）, the lower part of the Yanjiahe Fm on the Yangtze Platform in China, the lower Tal Fm in India, the Sukharikha Fm in Siberia, and the upper part of the Tsagaan Oloom Fm in Mongolia through biostigraphy. The lower part of the Yurtus Fm in the Tarim Basin is at the Nemakit-Daldynian stage, and the Precambrian/Cambrian boundary of the Aksu-Wushi area may be located in the phosphatic chert unit which just below the first appearance AHC acritarch assemblage zone. The negative δ13C excursion （N1） across the Precambrian/Cambrian boundary in the studied section may have resulted from oceanic overturning and sea level rise. 相似文献
10.
宁镇山脉小壳化石层时代的新认识 总被引：2，自引：1，他引：2
最新研究表明，句容仑山的小壳化石层和南京幕府山的一样，其层位都相当于下寒武统沧浪铺阶Ｐａｏｋａｎｎｉａ带，为我国下寒武统层位最高的一个小壳化石组合带。句容仑山当时位于台地边缘，缺失了早寒武世早期至沧浪铺期中期的沉积。 相似文献
11.
I.V. Korovnikov D.A. Tokarev N.V. Novozhilova A.A. Terleev 《Russian Geology and Geophysics》2018,59(2):186-192
The lower Ust’-Kundat Formation has been studied in detail in a section along the Kiya River (Kuznetsk Alatau, Altai-Sayan folded area). The section was deposited during the Tommotian stage and is a stratotype for the Lower Cambrian Ust’-Kundat sequence comprising several members of the Ust’-Kundat Formation. Member 2 contains newly discovered and previously known species of archaeocyathids near its top found stratigraphically lower than the oldest known archaeocyathan assemblage of the Nochoroicyathus mariinskii biozone. The found archaeocyaths cannot be dated precisely and may have either Tommotian or Atdabanian ages. Small shelly fossils from the same section cover a large stratigraphic range as well. The findings call for updating the age of the upper Ust’-Kundat sequence and the Tommotian upper boundary in the regional stratigraphy of the Altai-Sayan folded area. 相似文献
12.
Multi-episodic (three episodes at least) hydrothermal silica chimneys are identified in the black chert successions (up to ～ 100 m thick locally), overlain by thick black shales (up to a few 100 m thick), in the Ediacaran–Cambrian boundary successions along the southern marginal zone of the Yangtze Platform, South China. Their occurrences are constrained within the lowermost Cambrian by the SHRIMP U–Pb zircon dating and stable isotopic chemostratigaphic data, and are stratigraphically coincident with the negative isotopic excursions of organic carbon (～ 10‰ VPDB in magnitude) and sulfide sulfur (between 0 and 10‰ CDT), i.e., in bases of Nemakit–Daldynian and Tommotian stages in the Lower Cambrian. In this case, a causal link could have existed between which the hydrothermal venting could have released huge amounts of reduced silica-rich hydrothermal fluids with abundant 13C-depleted greenhouse gases (methane) and volcanic-originated H2S into the ocean and/or atmosphere, resulting in an extreme warm climate and oceanic anoxia, oceanic chemical perturbation, and subsequent massive precipitation of silica (chert), and large-magnitude negative isotopic excursions of organic carbon and sulfide sulfur. This scenario provides a unique chance to explore the causes of apparent tectono-depositional, oceanic and geochemical perturbations during this critical interval in South China and elsewhere. 相似文献
13.
梁山位于陕西省汉中市附近,属西南地台的北部边缘。1979年,我系陈润业教授带领学生在梁山大南沟实习,于下寒武统郭家坝组底部,厚度不到1米的含海绿石土黄色灰质砂岩及灰白色砂质灰岩中,首次发现了小壳动物化石(图1),并提出了梁山地区有相当于梅树村期沉积的可能性。 相似文献
14.
Definition of early Cambrian chronostratigraphic boundaries is problematic with many subdivisions still awaiting ratification. Integrated multi-proxy data from well-resolved regional-scale schemes are ultimately the key to resolving broader issues of global correlation within the Cambrian. In Australia, early Cambrian biostratigraphy has been based predominantly on trilobites. Phosphatic shelly fauna have great potential as biostratigraphic tools, especially in pre-trilobitic strata because they are widespread and readily preserved, but they have remained underutilised. Here we demonstrate their value in a new biostratigraphic scheme for the early Cambrian of South Australia using a diverse shelly fauna including tommotiids, brachiopods, molluscs and bradoriids.Biostratigraphic data are derived from ten measured stratigraphic sections across the Arrowie Basin, targeting Hawker Group carbonates including the Wilkawillina, Wirrapowie and Ajax limestones and the Mernmerna Formation. The stratigraphic ranges of shelly fossils are predictable and repeatable across the Arrowie Basin, allowing three discrete shelly biozones to be identified, spanning Terreneuvian, Stage 2 to Series 2, Stages 3–4. The Kulparina rostrata Zone (new) and part of the overlying Micrina etheridgei Zone (new) are pre-trilobitic (predominantly Terreneuvian). The Cambrian Series 2, Stage 3 Dailyatia odyssei Zone (new) features a very diverse shelly fauna and will be described in detail in a separate publication. These zones provide robust means to correlate Terreneuvian–Series 2 successions in neighbouring coeval basins in Australia, particularly the Stansbury Basin. Wider correlation is possible throughout East Gondwana, and especially with South China. 相似文献
15.
本文报道新疆阿克苏地区寒武纪幸运期最早期的小壳化石组合。化石产自玉尔吐斯组底部,包括：Protohertzina anabarica Missarzhevsky, 1973、Protohertzina unguliformis Missarzhevsky, 1973、Anabarites trisulcatus Voronova and Missarzhevsky, 1969、Anabarites ternarius Missarzhevsky in Rozanov et al., 1969、Cambrotubulus decurvatus Missarzhevsky in Rozanov et al., 1969、Olivooides sp.、Kaiyangites novilis Qian and Yin, 1984以及海绵骨针化石。据此可以在新疆阿克苏地区玉尔吐斯组下部建立Anabarites trisulcatus-Protohertzina unguliformis组合带。该组合带下界以Anabarites trisulcatus、Protohertzina ungulifo... 相似文献
16.
The Marwar Supergroup of the Bikaner-Nagaur Basin is composed of sediments deposited from the late Neoproterozoic (Ediacaran) to Upper Cambrian. The Nagaur Sandstone Formation of the Nagaur Group (uppermost division of the Marwar Supergroup) preserves trace fossils significant for establishing Early Cambrian biostratigraphic zones and depositional facies. Fifteen ichnospecies (and eight ichnogenera) identified in the Nagaur Sandstone Formation include “Treptichnus” pedum, Cruziana cf. tenella, Cruziana isp., Diplichnites ispp. A, B, and C, Gyrophyllites isp., Lockeia isp., Merostomichnites isp., Monomorphichnus gregarius isp. nov., Monomorphichnus isp., Planolites isp., Psammichnites isp., Rusophycus bikanerus isp. nov., Rusophycus cf. carbonarius, Rusophycus isp. and radial trace fossils.These trace fossils belong to ethological categories pascichnia, repichnia, cubichnia, and fodinichnia and represent arthropod and worm-like burrowing biota. The assemblage and a regional comparison with contemporaneous trace fossils in the eastern Gondwanan realm suggest that the sequence in the study area belongs to the Cruziana tenella Ichnozone and to Stage 2 (upper part of Terreneuvian), however the Middle Cambrian is not excluded. The trace fossil assemblage belongs to the archetypal Cruziana ichnofacies. Cross bedded sandstone, mud cracks and rainprints in the ichniferous strata of the Nagaur Sandstone Formation indicate deposition in an intertidal sand flat with channels that was exposed episodically. 相似文献
17.
B.B. Kochnev B.G. Pokrovsky A.B. Kuznetsov V.V. Marusin 《Russian Geology and Geophysics》2018,59(6):585-605
We propose a detailed δ13C curve for the Vendian and Lower Cambrian (Tommotian) strata of the central Siberian Platform. Two positive carbon isotope excursions identified near the base of the Yuryakh Formation (up to 5.5‰) and in the lower Bilir Formation (up to 5‰) are assigned to the lowermost and middle Tommotian, respectively. This correlation is supported by paleontological data, specific 87Sr/86Sr values (0.70845-0.70856), and similar C isotope record in coeval Early Cambrian basins. The documented minor vertical oscillations (a few meters) of these isotope excursions relative to the formation boundaries in remote boreholes is presumably caused by the spatiotemporal migration of facies. A high-amplitude negative δ13C excursion (-8 to -11‰) in the upper Nepa Regional Stage putatively corresponds to the global Shuram-Wonoka negative carbon isotope excursion (Middle Ediacaran). Carbonates of the lower Nepa Regional Stage (Besyuryakh Formation) demonstrate positive δ13C values (up to 5‰) and minimum 87Sr/86Sr ratios of 0.70796-0.70832. The C and Sr isotope record of the Nepa Regional Stage provides its robust correlation with the Dal’nyaya Taiga and Zhuya Groups of the Patom Foredeep. Micropaleontological data herein reported and glacial diamictites documented at the base of the Vendian sedimentary cover both in the central Patom Foredeep and on its periphery suggest a full stratigraphic volume of the Ediacaran System in the most stratigraphically complete sections of the central Siberian Platform. 相似文献
18.
CHEN Lan ZHONG Hong HU Ruizhong XIAO Jiafei TSAI Louis Loung-Yie LIN Andrew Tien-Shun ZOU Yanrong 《《地质学报》英文版》2012,86(5):1143-1153
The lower Cambrian Niutitang Formation, a widespread black shale deposition, is of geological interest because of its polymetallic beds, Cambrian explosion, depositional ages, dramatic environmental changes and so on. Previous study focused mainly on inorganic geochemistry and few studies have investigated the organic fractions of upper Neoproterozoic-lower Cambrian strata in South China. Here we report a study of biomarkers plus organic carbon isotopes for black shales from Ganziping, Hunan Province (China). All the saturated hydrocarbon fractions have a unimodal distribution of n-alkanes, a high content of short-chain alkanes and maximize at C 19 or C 20 (C 23 for sample Gzh00-1). The C 27 /C 29 sterane ratio ranges from 0.77 to 1.20 and 4-methylsteranes are in low abundance. These parameters indicate that algae and bacteria are the important primary producers. Furthermore, biomarker maturity proxies show the samples to be higher maturity. The low Pr/Ph values (<0.7) suggest that the samples were deposited under anoxic conditions and, likely, under stratified water columns. In addition, 25-norhopanes and gammacerane are present as diagnostic indicators of normal marine salinity and dysoxic to anoxic conditions. During the Early Tommotian, known to coincide with a transgression event, small shelly fossils increased in abundance and diversity. Moreover, positive δ 13 C org excursions close to 1.4‰ occur at the base of the Tommotian stage. In summary, the Early Cambrian black shales were deposited under dramatic paleoenvironmental changes, including oceanic anoxia, higher primary productivity and sea-level rise. 相似文献
19.
内蒙古白云鄂博地区具有世界上最大的稀有-稀土铁矿床,关于其时代归属尚存分歧。在都拉哈拉组(H3)与尖山组(H5)发现丰富的早寒武世微古植物化石,在尖山组(H5)硅质岩中发现早寒武世小壳化石,在哈拉霍疙特组(H8)确认了奥陶纪床板珊瑚的存在(包括块状群体与丛状群体),并首次发现大型古钵海绵化石与遗迹化石,在比鲁特组(H10)鲍玛序列中发现遗迹化石。初步确认,内蒙古商都地区三足化石(腕足类、头足类与腹足类)的层位可能为呼吉尔图组(或哈拉霍疙特组)。多门类化石的发现与确认,为重新认识白云鄂博超大型稀有-稀土铁矿床含矿地层时代提供了确凿的古生物化石证据,也为重新认识白云鄂博超大型稀有-稀土铁矿床的成矿地质背景开辟了新的研究思路,具有重要的地层学与大地构造学意义。根据多门类古生物化石组合与时代,将原白云鄂博群下部(H1~5)重新厘定为狭义的白云鄂博群,时代为早寒武世;原白云鄂博群上部(H6~15)重新命名为宽沟群,时代为早—中奥陶世,其间的假整合可能就是吉—黑地区的兴凯运动面。重新厘定的白云鄂博群与宽沟群一并划归天山-兴安地层区内蒙古草原地层分区,它是天山-兴安古生代海槽的一部分,并为海槽最南端的一个加里东褶皱带。 相似文献
20.
V. A. Luchinina I. V. Korovnikov N. V. Novozhilova D. A. Tokarev 《Stratigraphy and Geological Correlation》2013,21(2):131-149
The Early Cambrian history of the development of the Siberian Platform was marked by events of global significance. In the Early Cambrian the Siberian Platform was the centre of appearance of the first shelly fossils. For this reason, paleobiogeographical features of the distribution of fossils are of interest for scientists as a tool for paleogeographic and paleogeodynamic reconstructions. An analysis of changes in the Early Cambrian biota taxonomic diversity allowed us to reveal two major stages in its development: (1) Late Vendian (Tommotian and Atdabanian Stages): spreading of the Siberian biota worldwide; (2) Late Botomian-Toyonian Stages: an increase in the degree of endemism, extinction of archeocyaths, reduction in organogenic structures, deposition of black shales, and flourishing of trilobites. A permanent increase in the degree of biota endemism, which reached its maximum in the Botomian Stage, and the first appearance of migrants at the generic and species level at the same time, coincided with the first major transgressive phases. The study of the geographic distribution of diverse groups of the Early Cambrian fauna and calcareous algae of the Siberian basin allowed us to identify a number of biofacies of different age, whose boundaries do not coincide. The evolution and change in the taxonomic composition of the Siberian basin biota were affected by events of the first (Salair) phase of the Caledonian orogeny, manifested in the Altai-Sayan region much earlier than in other parts of the world and influencing the geological history of the Siberian Platform. These events resulted in the extinction and appearance of some specific groups of the Tommotian fauna in the Siberian Platform. 相似文献