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1.
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   

2.
Palynological investigation of the Cretaceous Abu Roash, Bahariya, Kharita, Alamein, Alam El Bueib and Betty formations, encountered in the Gebel Rissu-1 well, north Western Desert, Egypt yielded 27 species of pteridophytic spores, 24 of gymnosperm pollen, 25 of angiosperm pollen and 11 of dinoflagellate cysts in addition to some acritarchs, foraminiferal test linings and freshwater algae. This enabled us to recognize five miospore biozones arranged from youngest to oldest as: Classopollis brasiliensis–Afropollis cf. kahramanensis–Dichastopollenites ghazalataensis Assemblage Zone (Late Cenomanian); Elaterosporites klaszii–Sofrepites legouxae–Afropollis jardinus Assemblage Zone (Middle/Late Albian–Early Cenomanian); Pennipollis peroreticulatus–Duplexisporites generalis-Tricolpates Assemblage Zone (Early Aptian–Early Albian); Tucanopollis crisopolensis–Afropollis sp. Assemblage Zone (Barremian) and Appendicisporites cf. tricornitatus–Ephedripites spp. Assemblage Zone (Late Neocomian).The Early Cretaceous Kharita, Alam El Bueib and the Betty formations encountered in the Gebel Rissu-1 well are interpreted to indicate oxic proximal and distal shelf deposits, characterized by type III/IV, V kerogen, which is gas prone but having little potential to produce hydrocarbons. The Upper Cretaceous Abu Roash and Bahariya formations are characterized by a distal suboxic–anoxic and marginal dysoxic–anoxic environment, and their kerogen type III/II indicates gas/oil prone nature. The Bahariya and Kharita Albian–Cenomanian sediments in the present study witnessed the onset of a semi-arid to arid climate, with local or seasonal humid conditions, based on the continuous high abundance of the elaterates pollen and Afropollis-producing plants that inhabited the paleotropical humid coastal plains.  相似文献   

3.
Palynological and palynofacies analyses were carried out on some Cretaceous samples from the Qattara Rim-1X borehole, north Western Desert, Egypt. The recorded palynoflora enabled the recognition of two informal miospore biozones arranged from oldest to youngest as Elaterosporites klaszii-Afropollis jardinus Assemblage Zone (mid Albian) and Elaterocolpites castelainii–Afropollis kahramanensis Assemblage Zone (late Albian–mid Cenomanian). A poorly fossiliferous but however, datable interval (late Cenomanian–Turonian to ?Campanian–Maastrichtian) representing the uppermost part of the studied section was also recorded. The palynofacies and visual thermal maturation analyses indicate a mature terrestrially derived organic matter (kerogen III) dominates the sediments of the Kharita and Bahariya formations and thus these two formations comprise potential mature gas source rocks. The sediments of the Abu Roash Formation are mostly dominated by mature amorphous organic matter (kerogen II) and the formation is regarded as a potential mature oil source rock in the well. The palynomorphs and palynofacies analyses suggest deposition of the clastics of the Kharita and Bahariya formations (middle Albian and upper Albian–middle Cenomanian) in a marginal marine setting under dysoxic–anoxic conditions. By contrast, the mixed clastic-carbonate sediments of the Abu Roash Formation (upper Cenomanian–Turonian) and the carbonates of the Khoman Formation (?Campanian–Maastrichtian) were mainly deposited in an inner shallow marine setting under prevailing suboxic–anoxic conditions as a result of the late Cenomanian and the Campanian marine transgressions. This environmental change from marginal to open (inner shelf) basins reflects the vertical change in the type of the organic matter and its corresponding hydrocarbon-prone types. A regional warm and semi-arid climate but with a local humid condition developed near/at the site of the well is thought to have prevailed.  相似文献   

4.
Early Cretaceous sediments of Aptian–Albian age outcrop at Munday’s Hill Quarry, Bedfordshire, England. Previous papers describing the section have resulted in different terminologies being applied. The Lower Cretaceous in Bedfordshire is represented by sediments belonging to the Lower Greensand Group and the Gault Clay Formation. Within the Lower Greensand Group in the study area the Woburn Sands Formation, are of Aptian–Albian age. Selected samples have been analysed for palynology. The analysis reveals diverse palynomorph assemblages, including well-preserved dinoflagellate cysts and sporomorphs. Comparison of the assemblages with published records indicates that the lower samples are of Late Aptian age. Forms recorded include common Kiokansium unituberculatum, Cerbia tabulata, Aptea polymorpha and Cyclonephelium inconspicuum. An Early Albian age is indicated for the uppermost sample.  相似文献   

5.
The Dalichai Formation with an age of Late Bajocian-Late Callovian was sampled in Central Alborz Mountains of northern Iran and studied for palynological, palaeobiogeographical and palynocorrelation purposes. Palynological studies revealed diverse and well-preserved dinoflagellate cyst assemblages and lead to identification of three zones i.e., Cribroperidiniumcrispum (Late Bajocian), Dichadogonyaulaxsellwoodii (Bathonian to Early Callovian) and Ctenidodiniumcontinuum (Early to Middle Callovian) Zones. Subzone a of the D. sellwoodii Zone (Early to Middle Bathonian) was also differentiated. This biozonation corresponds to those recognised in Northwest Europe. Furthermore, the ammonoid families recorded including Phylloceratidae, Oppeliidae, Reineckeiidae, Perisphinctidae, Haploceratidae, Parkinsoniidae and Sphaeroceratidae, which confirm the Late Bajocian to Late Callovian age, are quite similar to those of Northwest Europe and the northwestern Tethys. The close similarities of the dinoflagellate cyst assemblages and ammonite fauna of northern Iran with those of Northwest Europe and the northwestern Tethys during the Middle Jurassic indicate direct but episodic marine connection and faunal exchange between the two areas.  相似文献   

6.
Stable C and O isotope records were obtained from carbonate rocks spanning the Hauterivian to Cenomanian interval collected in several sections from the carbonate platform of Pădurea Craiului (Apuseni Mountains, Romania). In the absence of some key biostratigraphic marker species, stable isotopes were applied as a tool for stratigraphic correlation and dating. The composite δ13C and δ18O curves for the Early Cretaceous shows variable conditions with large positive and negative excursions and provide information on past environmental changes. The Hauterivian and the Barremian limestones (Blid Formation) display lower δ13C values (−2.8‰ to +2.9‰) relative to the Aptian–Albian deposits (−2.6‰ to +5.4‰) (Ecleja, Valea Măgurii and Vârciorog Formations). The red detrital formation (Albian–Cenomanian) is characterized by a highly variable distribution of the δ13C values (−3.5‰ to +3.9‰). Based on the similarities between the C-isotope curve established in Pădurea Craiului and from other sections in the Tethyan and the Pacific regions, two major oceanic anoxic events characterized by δ13C positive excursions were clearly recognized. The first is the OAE1a event (Early Aptian) in the upper part of the Ecleja Formation and the Valea Măgurii Formation. The second is the OAE1b event (Late Aptian–Albian) in the upper part of the Vârciorog Formation and in the Subpiatră Member. The position of the Aptian/Albian boundary is estimated to be at the upper part of the Vârciorog Formation, immediately after the beginning of the δ13C positive excursion. The δ13C data show major negative excursions during the Barremian (Blid Formation), Early Aptian (Ecleja Formation), and Late Aptian (Vârciorog Formation). The O isotope variation pattern (−10.2‰ to −2.1‰) is consistent with progressively warming temperatures during the Early Barremian followed by a cooling period. A subsequent warming period culminated in the Early Aptian. A significant cooling phase corresponds to the Late Aptian and Early Albian and the climate cooled again during the Late Albian and into the Early Cenomanian stage. The data provide a better understanding of the Early Cretaceous sedimentation cycles in Pădurea Craiului and create a more reliable framework for regional correlations.  相似文献   

7.
列举并尝试对比了非洲早白垩世脊椎动物化石的主要产地。晚侏罗世(坦桑尼亚的敦达古鲁基默里奇期提塘期)至白垩纪最早期(南非的阿尔戈阿盆地凡兰吟期)的组合中含有剑龙、腕龙和梁龙,到前阿普特期(欧特里沃期巴列姆期?)被另一组合所取代。这一更年轻的组合中含有重爪龙亚科棘龙类、大头鳄类鳄鱼Sarcosuchus以及大型禽龙,它们主要来自尼日尔(ElRhaz组和喀麦隆(Koum组),部分来自利比亚(Cabao组)和突尼斯(Douiret组),后两组中还含有鲨鱼Priohybodus ar ambourgi。阿普特期(?)至早阿尔必期组合中仍含有禽龙,但是棘龙科棘龙类取代了重爪龙亚科。早塞诺曼期组合(Bahariya,Kem Kem)以恐龙Spinosaurus、Carcharodonto saurus,鲨鱼(Onchopris tisnumidus)和鳄鱼(利比亚鳄类、无棘腔鳄类)为特征。由此可知,中非的一些原先被认为是早白垩世的地层(坦桑尼亚的Galula组、马拉维的含恐龙层)为晚白垩世。脊椎动物化石在非洲陆相地层的对比中具有重要作用。  相似文献   

8.
The Lower Cretaceous series, in the Western Saharan Atlas, shows important detritic deposits, particularly continental to nearshore red sandstones. Lithologically, it is an alternation of red clay and sandstone intercalated with some carbonate levels at the lower part of the series. These series can be subdivided into three lithostratigraphic units corresponding to Valanginian-Hauterivian, Barremian, and Aptian-Lower Albian. The lithostratigraphic analysis used to reconstitute the important subsidence in the Lower Cretaceous period, particularly in the Lower Albian. The Lower Cretaceous series could be considered as a geodynamic model characterized by individualization of independent depocenter filled with different detritic material and separated by Jurassic structures. This new situation appeared in the beginning of Lower Cretaceous (Valanginian-Hauterivian), following the Neocimmeriean tectonic phase, and it is increasing in the Early Albian, where differences of thicknesses are more important and allow the distinction of the depocenter. The biostratigraphic analysis of the clay samples yielded some foraminifera and palynomorphs. Benthic and planktonic foraminifera confirmed the Hauterivian age of the basal formation, also, two dominant forms of palynomorphs were recognized; according to the large stratigraphic distribution of the identified forms, it can be attributed to the Lower Cretaceous.  相似文献   

9.
Diverse thoracican cirripedes from the Hauterivian of the Hannover district of northern Germany are described, including seven species, belonging to five genera. Of these, a new genus belonging to the Scalpellidae, Jaegerscalpellum, includes one Hauterivian species, J. elegans sp. nov., an Aptian species, J. comptum (Withers, 1910) and an Albian species, J. politum (Darwin, 1851) are also referred to it. A new Cretiscalpellum, C. mutterlosei sp. nov. is described from the Hauterivian, and C. matrioni sp. nov. is described from the Middle Albian of France. The oldest record of the Unilatera Gale, 2018, Pedupycnolepas pulcher sp. nov. is described from the Hauterivian; this displays typical shell structure of the group, retained by living Verrucidae. Finally, four species of Zeugmatolepadidae, subfamily Martillepadinae, are recorded from the Hauterivian, including Martillepas hausmanni (Koch and Dunker, 1836), M. decoratus sp. nov., M. auriculum sp. nov. and Etcheslaepas borealis (Collins, 1990). The Hauterivian fauna from Hannover shows affinities both with Late Jurassic and later Cretaceous (Aptian-Cenomanian) forms, and includes the earliest scalpellids, unilateran (Pedupycnolepas) and Cretiscalpellum species known. It constrains the age of the Cretaceous cirripede evolutionary radiation to the earliest Cretaceous.  相似文献   

10.
We present new data on the geologic position, composition, and isotope characteristics of the Early Cretaceous granitoids of the Samarka terrane, Sikhote-Alin’, formed on a transform continental margin. Geological and geochronological data show that these granitoids were generated at two stages of magmatism: in the first half (Hauterivian–Barremian, 130–123 Ma) and second half (Albian–Cenomanian, 110–98 Ma) of the Early Cretaceous. Granitoids of the first stage form an autonomous (free of basic precursors) unimodal melanogranite–granite association and are characterized by normal alkalinity with domination of K over Na, low contents of Ca, and elevated contents of Al2O3. By composition, these are S-granites with a model Nd age of ∼1.3 Ga. Granitoids of the second stage are of more diverse petrogeochemical types. They show wider variations in K/Na and A/CNK, are richer in Ca and, sometimes, Sr, and are poorer in P than the granitoids of the first stage. Their compositions form a continuous trend from S- to I-granites, and their model Nd age is ≤1.2 Ga. Comparison of the petrochemical, trace-element, and isotope characteristics of the Early Cretaceous granitoids and upper-crustal rocks (sandstones and siltstones of the turbidite matrix of a Jurassic accretionary prism and basalts from the inclusions in it) of the Samarka terrane and the coeval garrboids has shown that the potassic S-granitoids formed at the early (Hauterivian–Barremian) stage of magmatism as a result of the anatexis of upper-crustal sedimentary rocks. At the late (Albian–Early Cenomanian) stage, the intrusion of mantle magmas led to a temperature increase in the lower crust, which favored more active anatexis, involvement of high-melting substrates (oceanic basalts) in the granite formation, and interaction of mantle and crustal magmas. This resulted in a great diversity of granitoids (from S- to I-type).  相似文献   

11.
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   

12.
This paper contains the results of a comprehensive study of the standard Rarecostites subarietis Subzone of the upper Bajocian Parkinsonia parkinsoni Zone in sections on the Kyafar River (a tributary of the Bolshoi Zelenchuk River, Karachay-Cherkessia, Russia). The subzone is represented by shales with marl interbeds and sideritic concretions of the upper member of the Djangura Formation. The taxonomic composition and distribution of ammonites, foraminifers, ostracodes, dinoflagellate cysts, and miospores are established. The characteristic assemblages recognized of microfauna and palynomorphs enabled the recognition of foraminiferal and dinocyst biostratigraphic units for this Middle Jurassic interval. The index fossils are illustrated.  相似文献   

13.
H.G. Owen   《Cretaceous Research》2007,28(6):921-938
The ammonite biostratigraphy of the 279.35 m of sediments of mid-Late Albian–Early Albian age traversed by the Kirchrode II (1/94) boring is described. The borehole was drilled in the Hermann-Löns Park, Kirchrode (Hannover), northwest Germany, in the central region of the Lower Saxony sedimentary basin. The core commenced within the Kirchrode Mergel Member of the Gault Formation in sediments of Callihoplites auritus Subzone age and showed a Late Albian ammonite zonal succession similar to that previously described by Wiedmann and Owen from the lower part of the nearby Kirchrode I (1/91) core, with which it is correlated. The thick underlying clay sediments of the Minimus Ton Member (Middle Albian–late Early Albian) provided a relatively sparse ammonite fauna. In the Middle Albian part of the sediment succession, several hiatuses are present and only sediments of the lower Euhoplites loricatus Zone (Anahoplites intermedius Subzone) and the Hoplites dentatus Zone (Hoplites spathi Subzone) have been identified. This is followed downward by a thick sedimentary succession through the upper part of the Early Albian Douvilleiceras mammillatum Superzone (Otohoplites auritiformis Zone). Earlier mammillatum and perhaps latest Leymeriella tardefurcata Zone portions of the core straddling the Minimus Ton/Schwicheldt Ton boundary, did not yield ammonites. The underlying sediments at the top of the Schwicheldt Ton Member, consist of dark clays and mudstones with a good representation of the Leymeriella (Neoleymeriella) regularis Subzone and the uppermost part of the Leymeriella acuticostata Subzone (Leymeriella tardefurcata Zone). Of particular importance is the succession through the sediments of the L. (N.) regularis Subzone, hitherto poorly known in north Germany. A brief comparison and correlation is made with other surface and borehole sections in northern Germany and elsewhere. The Boreal and more cosmopolitan Tethyan elements of the fauna are indicated and discussed. An appendix of ammonites obtained from the Mittellandkanal section at Misburg of latest Albian, Arraphoceras (Praeschloenbachia) briacensis Subzone age, completes the study.  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.
The siliciclastic sediments of the Itapecuru Formation occur in a large area of the Parnaíba Basin and its deposits crop out along the Itapecuru River, in Maranhão State, northern Brazil. The palynological analysis of the Igarapé Ipiranga and Querru 1 outcrops strata yields a rich and diversified data. The presence of index-palynofloras in assemblages allows the identification of the Complicatisaccus cearensis Zone, of Late Aptian-Early Albian age. Terrestrial palynomorphs are abundant in the assemblages, being represented by bryophytes and pteridophytes, especially perisporate trilete spores (Crybelosporites and Perotrilites), and gymnosperms and angiosperms (Afropollis and Elaterosporites). The composition of palynological assemblages suggests the presence of moist soils for both outcrops. Acritarchs were recovered in the Querru 1 outcrop, which suggest a marine setting supporting a tidal flat environment indicated by facies associations. Furthermore, reworked Paleozoic palynomorphs were observed in the Querru 1 outcrop. The microflora from Igarapé Ipiranga outcrop suggests terrestrial environment corroborating with floodplain environment indicated by facies association.  相似文献   

16.
江苏白垩纪孢粉组合序列   总被引：9，自引：5，他引：4  
根据近年来获得的孢粉化石材料和前人资料 ,建立了江苏白垩纪的孢粉组合序列 ,它们是 :　 1)贝里阿斯期至凡兰吟期 (Berriasian— Valanginian)的 Schizaeoisporites- Classopollis annulatus- Ginkgocycadophytus nitidus组合 (云合山组 ) ;　 2 )阿普特期至阿尔必期 (Aptian— Albian )的 Cicatricosisporites- Classopollis annulatus-Psilatricolpites组合 (葛村组 ) ;　 3)土伦期 (Turonian )的 Schizaeoisporites- Polycingulatisporites- Cycadopites-Cranwellia组合 (浦口组 ) ;　 4)科尼亚克期至桑顿期 (Coniacian— Santonian)的 Schizaeoisporites- Classopolisannulatus- Lytharites组合 (赤山组 ) ;　 5 )坎潘期 (Campanian )的 Schizaeoisporites- Tricolporopollenitesmicrocirculatus- Betpakdalina组合 (泰州组下部 ) ;　 6 )马斯特里赫特期 (Maastrichtian)的 Pterisisporites-Exesipollenites- K urtzipites组合 (泰州组上部 ) ;　欧特里沃期至巴列姆期 (Hauterivian— Barremian)和塞诺曼期(Cenom ainan)的暂缺。  相似文献   

17.
黑龙江省东部中侏罗世至早白垩世沟鞭藻组合序列   总被引：5，自引：0，他引：5  
祝幼华  何承全 《地层学杂志》2003,27(4):282-288,T001
对近二十年来黑龙江省东部海相侏罗纪—白垩纪沟鞭藻地层资料进行了综合研究 ,首次为该地区建立起侏罗纪—白垩纪沟鞭藻地层序列 ,主要包含 7个组合带 (含 3个高峰带 ) ,其中绥滨地区 Callovian— Valanginian期有 4个带 ;鸡西盆地早白垩世也有 4个带 (其中包括与绥滨地区早白垩世早期同时异相的一个 )。它们自下而上为 :1)绥滨组的 Pareodinia ceratophora- N annoceratopsispellucida组合带 ;　 2 )东荣组下部的 Gonyaulacysta jurassica组合带 (高峰带 ) ;　 3)东荣组上部的 Amphorula delicata组合带 ;　 4 )东荣组最上部的海相 Oligosphaeridium pul-cherrimum组合带 (高峰带 )或鸡西盆地滴道组的微咸水—半咸水的 Vesperopsis didaoensis- L agenorhytis granoru-gosa组合带 ,两者为同时异相关系 ;　 5 )城子河组下部海相层的 Odontochitina operculata- Muderongia tetracantha组合带 (该带可进一步划分出 2个亚组合带 ) ;　 6 )城子河组上部海相层的 Canningia reticulata组合带 ;　 7)穆棱组下段的 Cribroperidinium ?parorthoceras组合带 (高峰带 )。  相似文献   

18.
Early and early middle Cenomanian turrilitid ammonoids from the upper part of the Albian–Cenomanian Aitamir Formation of the Koppeh Dagh (northeast Iran) are described, illustrated and placed in an integrated stratigraphic context. The Aitamir Formation represents a graded siliciclastic shelf system and the turrilitid faunas comprise eight different species. Representatives of Mariella and Hypoturrilites have been recorded from a lower Cenomanian horizon in the Ghorghoreh section, corresponding to the Mantelliceras mantelli ammonite biozone. Mariella bicarinata (Kner, 1852) and H. wiedmanni Collignon, 1964 are recorded for the first time from Iran and the larger palaeobiogeographical area, respectively. The horizons with Turrilites costatus and T. scheuchzerianus at Taherabad can be dated as early middle Cenomanian Acanthoceras rhotomagense Zone, T. costatus Subzone. Concentrations of ammonoids commonly occur above regressive sandstone units, at the transition into overlying deeper marine shale units and in their lower parts, respectively. Such intervals represent the early transgressive systems tract of depositional sequences and may thus be regarded as early transgressive, slightly condensed shell accumulations. The uppermost lower to lower middle Cenomanian succession at Taherabad is of striking bio-, event- and sequence stratigraphic similarity to contemporaneous sections in northwest Europe. It reflects deposition during falling and low sea-level associated with the latest early Cenomanian unconformity SB Ce 3 as well as the pulsating transgressive development during the early middle Cenomanian, including levels correlative to the arlesiensis, primus and Mid-Cenomanian events in northwest Europe.  相似文献   

19.
Elaphrosaurinae is an enigmatic clade of gracile ceratosaurian theropod dinosaurs known from the Late Jurassic of Africa (Elaphrosaurus bambergi) and Asia (e.g., Limusaurus inextricabilis), and the early Late Cretaceous of Argentina (Huinculsaurus montesi). Elaphrosaurinae is often placed within Noasauridae as the sister taxon to Noasaurinae, a clade of small-bodied theropods that lived in South America, Africa, Madagascar and India throughout much of the Cretaceous. Herein, we report the first evidence of Elaphrosaurinae from Australia: a nearly complete middle cervical vertebra from the upper Lower Cretaceous (lower Albian) Eumeralla Formation of Cape Otway, Victoria, Australia. The fact that this site would have been situated at ~76°S towards the end of the Early Cretaceous (~110–107 Ma) implies that elaphrosaurines were capable of tolerating near-polar palaeoenvironments, whereas its age indicates that elaphrosaurines persisted in Australia until at least the late Early Cretaceous. The new Australian elaphrosaurine, in tandem with the recently described Huinculsaurus montesi from the Cenomanian–Turonian of Argentina, implies that the spatiotemporal distribution of Elaphrosaurinae has heretofore been greatly underestimated. Historic confusion of elaphrosaurines with coelurosaurs, especially ornithomimosaurs, coupled with our generally poor understanding of noasaurid evolution, might explain the apparent dearth of fossils of this theropod clade worldwide.  相似文献   

20.
A palynological analysis of a Late Jurassic–Early Cretaceous succession in the Himalayan Tethys, Gyangzê County, southern Xizang (Tibet) provides, for the first time, evidence of changing palynofloras through the Jurassic/Cretaceous (J/K) boundary. Species that are stratigraphically important and potential markers for delineating the boundary include both miospores and dinoflagellate cysts. The presence of the spores Crybelosporites sp. cf. stylosus, Foraminisporis wonthaggiensis, Jiaohepollis verus and Toroisporis welzowense and the cysts Cassiculosphaeridia delicata and Rhynchodiniopsis serrata imply that the J/K boundary is between samples 06-21-1 and 06-21-3. The occurrence of Aequitriradites spinulosus and Cicatricosisporites spp. a little below this level and of ?Dictyotosporites sp. cf. speciosus slightly above it is also significant. These results show that it is possible to locate the J/K boundary in the Himalayan Tethys near top of the Weimei Formation and the lower part of the Gyabula Formation in southern Xizang. This succession also contains various marine invertebrate fossils, including ammonites, bivalves and belemnites, and thus has considerable potential for erecting an integrated biostratigraphy around the J/K boundary in the eastern Tethyan realm. Palynofloristic correlation implies a more northerly location for the fossil locality at Gyangzê than that of northwest Australia during the latest Jurassic and earliest Cretaceous, which can be further constrained to around 43°S.  相似文献   

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