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The belemnite species Praeactinocamax primus (Arkhangelsky, 1912) and Belemnocamax boweri Crick, 1910 are described from the Cenomanian of the abandoned limestone quarry section of Hoppenstedt (Sachsen-Anhalt, northern Germany). They co-occur in the upper part of a prominent tripartite bioclastic limestone bed associated with the ammonite Acanthoceras rhotomagense, indicating the primus Event of the lower middle Cenomanian A. rhotomagense ammonite Zone. An integrated stratigraphical calibration including carbon stable isotope correlation to southern England suggests that the belemnite event horizon at Hoppenstedt occupies exactly the same chronostratigraphical position as elsewhere, highlighting the strictly isochronous character of the primus Event across northwestern Europe. Furthermore, stratigraphical gaps in the Hoppenstedt succession are evaluated. 相似文献
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本文将西藏札达盆地河湖相地层重新划分为第四系下更新统香孜组(Qp1-1x)、新近系上新统古格组(N22g)和上新统托林组(N21t)。河湖相地层的古地磁法和ESR法测年结果表明,札达盆地内河湖相沉积地层的形成时代为新近纪上新世—第四纪早更新世。根据该套河湖相地层沉积演化和其中的孢粉组合特征、河湖相沉积中所发现的各种古动植物化石等的综合分析,笔者对札达盆地上新世—早更新世的古植被、古环境与古气候演变进行了探讨。结果表明,札达地区上新世—早更新世气候经历了从湿热—温暖潮湿—偏冷潮湿—寒冷干旱的变化,以及植被从森林—灌木—草原的逐渐演化。可将札达盆地上新世—早更新世环境演化划分为7个大的阶段,其总体特征是15.4~4.4Ma,札达地区处于亚热带湿热气候环境;24.4~3.95Ma,为暖温带温暖潮湿气候;33.95~3.5Ma,为偏凉潮湿阶段,气候开始转冷;43.5~3.2Ma,为温暖潮湿阶段;53.2~2.9Ma,气候转为偏冷潮湿阶段;62.9~2.57Ma,该阶段气候偏冷而干旱,整体较为干冷;72.57~1.36Ma,气候寒冷而干旱。表明自上新世—早更新世,该区的古气候环境在逐渐变干、变冷的总趋势上,经历了多次明显的冷暖与干湿波动。 相似文献
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J. Pinchin 《Australian Journal of Earth Sciences》2013,60(4):437-445
The results of the seismic surveys recorded during 1963 and 1968 for Marathon Petroleum and Crusader Oil in the Laura Basin, north Queensland, have been reinterpreted. Seismic reflections which dip almost continuously from 0.6 to 4.0 seconds reflection time may come from the base of and within an 8000 m sequence of Permo‐Carboniferous sediments, which may underlie the flat‐lying Mesozoic Laura Basin sediments and overlie the heavily folded Carboniferous‐Devonian sediments in the Hodgkinson Basin. Further seismic investigation of this area is recommended since a thick Permo‐Carboniferous sedimentary section here could be prospective for hydrocarbons. 相似文献
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The Ediacaran to lowermost Cambrian successions of south‐eastern Uruguay preserve an unusual and significant record of deposits generated during the Gondwana assembly (ca 590 to 535 Ma). This study presents a review of data obtained through extensive field‐based mapping coupled with detailed sedimentology and stratigraphy of key formations. The geological units within the study area consist of the Maldonado Group (Playa Hermosa, Las Ventanas and San Carlos formations), the Arroyo del Soldado Group (Yerbal, Polanco Limestones, Barriga Negra and Cerro Espuelitas formations) and the Arroyo de la Pedrera Group (Piedras de Afilar and Cerro Victoria formations). The Maldonado Group is characterized by a glacially influenced volcanogenic‐sedimentary sequence with ice‐rafted debris and dropstones in the Playa Hermosa and Las Ventanas formations. The Arroyo del Soldado Group is a mixed siliciclastic‐carbonate succession, mainly represented by an intercalation of basal pink dolostones, banded siltstones, rhythmites of dolostone‐limestone, iron formations, cherts and conglomerates. Carbonates in the Polanco Limestones Formation are characterized by a negative δ13C excursion up to ?3·26‰ PeeDeeBelemnite. The Arroyo de la Pedrera Group consists of quartz arenites and stromatolitic/oolitic dolostones. Preliminary data indicate that the Precambrian–Cambrian could be contained within or at the base of this group. The entire succession is almost 6000 m thick, and contains a rich fossil assemblage composed of organic‐walled microfossils and small shelly fauna, including the index fossil Cloudina riemkeae. The stratigraphic and chemostratigraphic features are suggestive of a Gaskier age (ca 580 Ma) for the basal glacial‐related units. In this scenario, the results show the importance of lithostratigraphic, biostratigraphic and chemostratigraphic data of these Ediacaran units in the global correlation of terminal Proterozoic sedimentary rocks. 相似文献
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Late Albian ammonite faunas from the Aitamir Formation of the Koppeh Dagh Basin in northeast Iran are described and illustrated. These comprise 14 taxa, several of which are recorded from Iran for the first time, namely Anahoplites planus (formerly recorded from central Iran in open nomenclature only), Semenoviceras solidus, Epihoplites (Metaclavites) iphitus, Hysteroceras orbignyi and Pseudhelicoceras robertianum. New records of Placenticeras grossouvrei extend the stratigraphic range of this species downwards into the Late Albian; previously it was known from the Early and Middle Cenomanian only. The record of the rare E. (M.) iphitus fills a palaeobiogeographic gap between Crimea and Tajikistan, and the holotype of Spath is re-illustrated here. Additionally, Epihoplites trapezoidalis, from the Late Albian of Tajikistan, is relegated into the synonymy of Spath's species. A large number of taxa typical of the Late Albian (upper part of the Gault Clay Formation) of northwest Europe indicate close palaeobiogeographic affinities with the Koppeh Dagh Basin and faunal exchange across the Russian Platform and Transcaspia. The stratigraphic succession of the ammonite faunas is used for a biostratigraphic subdivision of the upper Aitamir Formation. 相似文献
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During the Cainozoic there was widespread volcanism, mainly basaltic, in eastern New South Wales. Numerous new K‐Ar ages, together with previously published results, provide information on the age of virtually all the main volcanic provinces, and indicate that the volcanism started about 70 m.y. ago in the Late Cretaceous, and was continuous from about 60 m.y. ago (Palaeocene) until about 10 m.y. ago (middle Miocene). There has been no volcanic activity since 10 m.y. ago. The ages of uplift of the Eastern Highlands are estimated from the relationship of the dated basaltic flows to the topography. A major uplift is deduced some time between the mid‐Cretaceous and late Oligocene, followed by a quiescent period. A further uplift started some time after the middle Miocene, and it continues to the present day. The highland was uplifted differentially both along and transverse to the axis. 相似文献
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Geologie en Mijnbouw - 相似文献