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1.
The brackish-water bivalve Waagenopema Tokuyama,1959 is reported from the Lower Jurassic Badaowan Formation at four localities,along the southern margin and western margin of the Junggar Basin. Taphonomic features recorded in the field indicate that it occurs in autochthonous or parautochthonous assemblages.The autecology of Waagenopema therefore yields information on the palaeoenvironment of the area.The restriction of Waagenopema to marine and brackish-water settings suggests that the sea water once reached these areas during the Sinemurian.This paper discusses the palaeogeographic implications and suggests an ingression of the sea water from the west to the western and southern part of the Junggar Basin.Additionally,the two Waagenopema species collected from the Haojiagou section in the Junggar Basin are taxonomically documented.  相似文献   

2.
The Sinuiju Formation in Paekto-dong, Sinuiju City in the Democratic People's Republic of Korea has yielded Mesozoic nonmarine bivalve fossils, which is the first occurrence of such in the DPRK. Based on these fossil specimens, a new Cretaceous bivalve assemblage, the Arguniella yanshanensis-Sphaerium anderssoni Assemblage is erected. This assemblage includes Arguniella yanshanensis, A. lingyuanensis and Sphaerium anderssoni and can be compared with the Jehol Biota. The age of the Sinuiju Formation is also clarified and on the basis of the bivalves and the presence of a Eosestheria–Ephemeropsis–Lycoptera(E–E–L) assemblage, the formation is not Upper Jurassic, but Lower Cretaceous in age.  相似文献   

3.
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   

4.
正1 Introduction The end-Triassic mass extinction event is one of the five global mass extinctions,and destroyed both the marine and terrestrial biological worlds.Though years the marine endTriassic mass extinction (ETE) event has been widely studied and discussed,and the standard marine Triassic/Jurassic boundary (TJB)(base-Jurassic) has also been determined.However,regarding the terrestrial world there are still lot of  相似文献   

5.
Based on the study of lithology, sedimentology and paleontology at the Permian-Triassic boundary in Liaotian, Northwestern Jiangxi Province, the sequence stratigraphy and depositional environments across the boundary are reconstructed. The top part of the Upper Permian Changxing Formation is composed of very thick-bedded ligh-colored dolomitic limestone formed in high deposition rate on carbonate ramp,which indacates a transgression systems tract (TST). The Lower Triassic Qinglong Formation shows continuous deposition with the underlying Upper Permian. The lower member of Qinglong Formation consists of calcareous shale, shelly limestome and dolomitic limestone with abundant bivalves (Claraia sp.) and trace fossills (Chondrites). The calcareous shale at the bottom of Lower Triassic indicates a calm deep water environment to form the condensed section (CS). The shelly limestome and dolomitic limeston with shell fossils, intraclast, algal ooide show clean but turbulent environment of carbonate ramp, which produce the deposition of highstand systems tract (TST).  相似文献   

6.
The Upper Carboniferous Zhanjin Formation has attracted much attention from geoscientists for containing glacial–marine diamictite and cold-water fauna typified by the bivalve Eurydesma.The presence of this Formation has provided important evidence for determining the northern border of Gondwana.Previous researchers have classified those strata north of Niangrong Co in the Gêrzê region as part of the Zhanjin Formation based on the presence of glacial–marine diamictite, although the absence of biological fossil evidence has defied clear age determination.Our field investigations first discovered large quantities of corals, sponges and bryozoans.All coral fossils were identified as belonging to the Hexacorallia subclass including 13 genera and 25 species, primarily including Conophyllia guiyangensis Deng et Kong, Coryphyllia regularis Cuif, Cuifia columnaris Roniewicz, Distichophyllia norica Frech, Distichophyllia gigas Vinassa de Regny, Pamiroseris rectilamellosa Winkler, Retiophyllia clathrata Emmrich, and Retiophyllia paraclathrata Roniewicz.Extensive biostratigraphic correlations show that the hexacorallia should belong to the Late Triassic, thereby negating the presence of the Zhanjin Formation in the study area.Based on analyses of sedimentary facies and detailed study of the glacial–marine diamictite as supposed by earlier researchers, the limestone blocks and gravels within the facies are slope facies olistostromes and waterway sediments from lime slurry debris flows in the submarine fan rather than primary sedimentary products.Among them, lenticular sandstone should be sequentially distributed waterway sand bodies, indicating that the strata have no glacial–marine diamictite.In addition, the rocks containing the mentioned fossils are just limestone blocks from olistostromes, and limestone gravels from waterways of submarine fans.Such a result further negates the presence of the Zhanjin Formation in the study area, and indicates that the age of the studied strata should be youner than the Late Triassic.Through regional stratigraphic comparisons and the study of tectonic settings of the strata, the sedimentary characteristics of the subject strata, including lithology, lithofacies and fossils, are confirmed to be similar to the widely distributed Sêwa Formation in this region.We thus infer that the strata belong to the Middle–Lower Jurassic Sêwa Formation.This finding is important for both studying paleogeography of Tibet and determining the northern boundary of Gondwana.  相似文献   

7.
正Objective Neocalamites is a common plant fossil from the Triassic to the Middle Jurassic. Neocalamites fossils are commonly found in coal-bearing sedimentary rocks of Rhaetian stage from South China and the Yanchang Group from North China(Mei and Liu, 2017). Moreover, the fossils also distribute in the Late Triassic such as the Babaoshan Group in Dulan and Darigemole Group in Gangcha of Qinghai Province, the Haojiagou Formation in Turpan and  相似文献   

8.
Nicol Morton 《《幕》》2008,31(4):420-422
The Jurassic is traditionally famous for shallow marine sediments that are often very fossiliferous, notably in Europe, where the standard chronostratigraphic subdivisions were established and defined. However, widespread marginal and non-marine Jurassic sediments are also known, and are of great importance for the wellpreserved terrestrial biotas they contain, as well as for their hydrocarbon and coal reserves. IGCP Project 506 is directed towards finding means of correlation between marine and non-marine Jurassic rocks, as a foundation for a better understanding of the evolution of the Earth during the Jurassic Period.  相似文献   

9.
The isotopic composition and parameters for deuterium excess of brines, which were sampled in the Si-chuan Basin, show obvious regularities of distribution. The brine isotopic composition shows distinct two systems of marine and terrestrial deposits, with the Middle Triassic strata as the boundary. Brine hydrogen isotopic composition of marine deposits is lower while oxygen isotopic composition is higher than that of the SMOW, respectively, indicating that the brines were derived from seawater with different evaporating degrees at different times. From the Sinian strata, up to the Cambrian, Permian Maokou Formation and the Triassic Jialingjiang Formation, the δD values of brines tend to become relatively positive with the strata becoming younger. Brines of terrestrial deposits are considered to have been derived from precipitation and their isotopic composition is close to the globe meteoric water line (GMWL). Brines of transitional deposits between marine and terrestrial ones (the Upper Triassic Xujiahe Formation) have δD and δ18O values falling between the two end members of marine deposit brines and precipitation, indicating that the brines are a mixture of precipitation and vaporing seawater. Water samples from the brine-bearing strata of different ages show various deuterium excesses (d) with an evident decreasing trend as the age of strata gets older and older. Brine-bearing strata of the Triassic Leikoupo-Jialingjiang Formation, the Permian Maokou Formation, the Cambrian and Sinian strata are all carbonate rocks which have experienced intensive water/rock reaction and the deuterium excess essentially changes with time. All brine-bearing-strata surrounding the basin or faults, as well as those brine wells exploited for resources, have been obviously influenced by the precipitation supply. Therefore, the deuterium excesses of their brines have increased to different extents, depending on the amount of involvement of meteoric water. The variation and distribution of d values of the brines from different Triassic strata are related to the embedded depth of the strata. The deuterium excesses of brines become lower with increasing burial depth of the strata.  相似文献   

10.
A new stegosaur species, Jiangjunosaurus junggarensis, gen. et sp. nov., is erected based on a specimen collected from the Upper Jurassic upper section of the Shishugou Formation in the Junggar Basin, Xinjiang, China. It represents the first stegosaur from the Jurassic of Xinjiang and increases the diversity of the dinosaur fauna in the Shishugou Formation. The new genus is characterized by symmetrical and proportionally wide tooth crowns, a sub-rectangular axial neural spine seen in lateral view, and large openings on the lateral surfaces of the cervical centra. A preliminary character analysis suggests that this new taxon is more derived than the Middle Jurassic stegosaur Huayangosaurus but more primitive than most other known stegosaur species.  相似文献   

11.
准噶尔盆地南缘三叠纪—侏罗纪之交的古气候*   总被引：3，自引：1，他引：2       下载免费PDF全文
准噶尔盆地南缘的郝家沟剖面三叠系—侏罗系连续发育,是研究三叠系—侏罗系界线及相关地质问题的重要剖面。孢粉分析发现,上三叠统郝家沟组以气候适应范围较宽的裸子植物花粉占优势,而在下侏罗统八道湾组下部主要适应温暖湿润气候的蕨类植物孢子含量明显增高,在组合中常占据优势地位,说明研究区早侏罗世气候比晚三叠世更为潮湿。沉积岩有机碳同位素分析结果显示,在剖面八道湾组下部的δ13C值总体低于-24.5‰,形成两次明显的负向偏移,同时采集的丝炭样品的分析结果也证明δ13C在八道湾组下部具有明显负向偏移。根据现代湖泊沉积有机质碳同位素与气候关系的研究成果,沉积有机质稳定碳同位素负偏是气候温暖潮湿化的反应,支持了孢粉研究的结果。以上表明,研究区侏罗纪之初的气候比晚三叠世更加炎热潮湿。  相似文献   

12.
准噶尔盆地早侏罗世八道湾组陆相沉积中发现海相瓣鳃类   总被引：2，自引：0，他引：2  
在陆相河湖沉积的八道湾组（早侏罗世）内,新发现一些海相瓣鳃类化石,表明当时准噶尔盆地在一短期内曾与海水相通,或者海水通过某一水系涌入该河湖区。从生态特征分析,当时可能为一泛滥平原。根据海相化石对化,化石产出层位八道湾组上部的时代可能属西湟缪尔期。  相似文献   

13.
在实测四棵树剖面的基础上,详细研究了其孢粉组合特征,建立了5个孢粉组合:1)Cameratitriletes和Zonotriletes-Protopinus-Cycadopites组合,2)Cyatheaceae-Pinaceae-Cycadopites组合,3)Cyatheaceae-Pinaceae-Quadraeculina-Cycadopites组合,4)Cyatheaceae-Quadraeculina-Piceaepollenites组合和5)Cyatheaceae-Clas-sopollis-Pinaceae组合,分别产于上三叠统的小泉沟群、下侏罗统的八道湾组和三工河组、中侏罗统的西山窑组和头屯河组。根据孢粉组合特征,结合岩性和沉积及区域资料,将三叠系-侏罗系界线定于38层和39层之间。  相似文献   

14.
Marine and non-marine facies of the Permian–Triassic boundary stratigraphic set (PTBST) are well developed in South China. Palynological assemblages enable subdivision and correlation of the Permian–Triassic boundary (PTB) rocks. Three palynological assemblages are recognized across the PTBST in two terrestrial PTB sections in western Guizhou and eastern Yunnan, South China. Assemblage 1 (Xuanwei Formation) is a Late Permian palynological assemblage dominated by ferns and pteridosperms, with minor gymnosperms. Most taxa are typical long-ranging Paleozoic forms, but the appearance of Lueckisporites confirms a Late Permian age for this assemblage. Assemblage 2 (PTBST) is marked by an abrupt decrease in palynomorph abundance and diversity, and thriving fungal/algal(?) spores. Assemblage 2 is still dominated by ferns and pteridosperms, with a few gymnosperms, but is characterized by a mixed palynoflora containing both Late Permian and Early Triassic elements. Most taxa are typical Late Permian ones also found in Assemblage 1, however, some taxa of Early Triassic aspect, e.g. Lundbladispora and Taeniaesporites, appeared for the first time. In Assemblage 3 (top Xuanwei Formation and Kayitou Formation), the proportion of gymnosperm pollen increases rapidly, exceeding that of ferns and pteridosperms, but the abundance of palynomorphs is still low. Typical Early Triassic taxa (such as Lundbladispora, Aratrisporites and Taeniaesporites) are present in greater abundance and confirms an Early Triassic age for this assemblage.  相似文献   

15.
Triassic–Jurassic sedimentary successions (Baluti and Sarki formations) in northern Iraq record a variety of environmental changes that may be related to global Triassic–Jurassic (Tr/J) boundary events. The diversity of some benthic fauna decreases through the transitional boundary beds. The coastal marine environment of the lower part of the Baluti Formation is followed by shallower tidal flat and supratidal marginal marine environments at the transitional boundary with the Jurassic‐age Sarki Formation. The alternating calcareous mudrocks and dolomitic limestones of the transitional succession are overlain by a succession of calcareous mudrocks and dolomicrites that form a dolocrete bed in the latest Triassic. The early Jurassic carbonates (lower part of Sarki Formation) were deposited in a shallow‐marine to lagoonal environment. Geochemical evidence supports this interpretation. TOC% increases towards the Tr/J boundary and the lower part of the Sarki Formation. This increase can be interpreted as resulting from the primary precipitation of dolocrete as palaeosol horizons. The variations in the oxygen isotope ratios mainly reflect the facies and diagenetic effects. Th/K ratio is generally constant and shows an increase in the calcareous mudrock beds of the upper part of the Baluti Formation, possibly related to the degradation of K‐bearing clay minerals. Low Th/U ratios are due to the depletion in thorium, typical of many marine carbonates rather than to an increase in authigenic uranium. This explanation is also corroborated by the presence of abundant fossils in some of the studied carbonates. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

16.
Recent collecting in exposures of the lowermost Burgersdorp Formation (Beaufort Group), of the Karoo Basin of South Africa, has revealed a previously unknown fish fauna from the Early Triassic (Scythian), lowermost Cynognathus Assemblage Zone (CAZ), which forms an important component of the total vertebrate assemblage. The newly discovered fish material includes lungfish, saurichthyids, and a large microfauna that includes numerous isolated chondrichthyan teeth, two fin spine fragments, and actinopterygian scales and teeth. The latest fish finds, together with the lowermost Cynognathus Assemblage Zone vertebrate faunas, make this Karoo Basin Assemblage Zone one of the most diverse Early Triassic faunal assemblages, comparable in faunal diversity to those from the Czatkowice Formation (Poland) and the Arcadia Formation (Australia). The presence of the lungfish Ptychoceratodus phillipsi in the early Middle Triassic Cynognathus Assemblage Zone (Subzone B), and in the underlying latest Early Triassic Cynognathus Assemblage Zone (Subzone A), indicates that these lungfish could serve as range index fossils within the CAZ, and thus are potentially useful biostratigraphic markers across the Early-Middle Triassic boundary. Furthermore the ‘new’ fish fauna provides a vital marine realm link in particular with the faunas of Madagascar and Australia, that is unavailable using the tetrapod faunal elements of the lower CAZ.  相似文献   

17.
新疆吐哈盆地侏罗系旋回地层的初步研究   总被引：4，自引：4，他引：4  
应用新疆吐哈盆地侏罗系 4口井 7个组的伽玛测井资料 ,进行高分辨率旋回地层的研究。结果表明 :依据412 .9ka的偏心率旋回 ,7个组旋回堆积速率 ( AR)的平均值为 0 .15 2 9m/ka,它与北美东部上三叠统 4个组合的Mc L aughlin旋回 AR平均值 0 .16 39m/ka相接近。本区与准噶尔盆地郝家沟八道湾组的野外剖面旋回地层对比 ,两者的优势旋回量度时间大体一致。吐哈盆地侏罗纪地层中在大约 3～ 10 m厚度、相当 2 0～ 6 0 ka时间的范围内有小规模的气候变化 ;而在 5 0～ 75 m厚度、约相当 10 0和 42 0 ka的时间中 ,又会出现较大的气候变化。  相似文献   

18.
Well-preserved and abundant Jurassic–Early Cretaceous palynomorph assemblages were recorded from the Kabrit-1 well, north Eastern Desert, Egypt. Thirty-one rock-cutting samples were analyzed and six rock units were differentiated. Seventy-one palynomorph species were identified from the productive samples. Six palynozones were differentiated, and they covered all the studied succession except for a palynomorph barren interval present in the uppermost part. These palynozones arranged in ascending order are as follows: two palynozones were recorded from the Middle-Upper Jurassic (Gonyaulacysta jurassica – Lithodinia jurassica Assemblage Zone and Klukisporites pseudoreticulatus- Systematophora penicillata – Escharisphaeridia pocockii Assemblage Zone) and the other four palynozones characterize the Lower Cretaceous deposits (Pilosisporites trichopapillosus – Cribroperidinium orthoceras Assemblage Zone; Dicheiropollis etruscus Interval Zone; Murospora florida – Afropollis operculatus Assemblage Zone and Afropollis jardinus Range Zone). We infer open marine conditions during deposition of the lower part of the Khalig El Ayoun Formation (Oxfordian-Kimmeridgian) and within the Kharita Formation (Albian), and shallow marine or coastal environments during deposition of the remainder of the studied succession. Paleobiogeographically, Late Jurassic index terrestrial palynomorph species documented here are in common with those previously recorded from North Africa, while marine dinocyst species are common to those documented from the West European and North American province. During the Early Cretaceous, the recorded terrestrial microfloral species were similar to those previously recorded from the West African-South American Province, while the marine dinocyst species were still related to the West European and North American marine palynofloral province.  相似文献   

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