Late Cenomanian–Early Turonian ammonites of the southern Tethys margin from Morocco to Oman: Biostratigraphy,paleobiogeography and morphology     

《Cretaceous Research》2013

The Cenomanian–Turonian ammonite biostratigraphical framework for the southern Tethys margin (North Africa, Middle East and the Arabian Peninsula) is becoming better understood. A first attempt at a synthetic range chart is presented, with 85 taxa and precise correlations for ammonites along a west–east transect from Morocco to Oman, inclusive of the Trans-Saharan Seaway as far south as northern Nigeria. On the basis of a critical review of ammonite taxonomy, 13 bioevents can be identified in the interval from the Late Cenomanian to the Early Turonian (c. 3.5 myr) with each bioevent corresponding to a time interval of approximately 270,000 years, on average. They are consistent throughout several regions along the southern Tethys margin, though some gaps remain, at least at the stage boundary. These bioevents are correlated with the zonation defined for the stratotype (GSSP) of the base of the Turonian in the Western Interior (USA). The paleobiogeographic distribution of ammonites reveals some endemism but the predominant picture is that of a homogeneous fauna throughout the area, even though distinct Boreal and Western Tethys (Atlantic domain) marine influences are evident. An interpretation of the evolution of conch morphology and ornamentation through the zones of the Late Cenomanian–Early Turonian is proposed.  相似文献   

A new sauropod dinosaur (Dinosauria,Sauropoda) from the late Early Cretaceous of the Ruyang Basin (central China)     

《Cretaceous Research》2013

A new long-necked sauropod dinosaur, Yunmenglong ruyangensis gen. et sp. nov., is erected on the basis of an incomplete skeleton from the late Early Cretaceous Haoling Formation of the Ruyang Basin, Henan Province. The characters of the anterior cervical vertebrae, the shape of the neural canal of the dorsal vertebra and the ball-shaped distal end of the neural spine of caudal vertebrae with coarse surfaces differ from other long-necked sauropod dinosaurs. The new genus has characters in common with both Euhelopus and Erketu; it represents the first long-necked sauropod dinosaur recorded from central China to date. The rod-like, well-developed epipophyses and the pleurocoels on the cervical vertebrae indicate that it may be close to Euhelopus, an observation also confirmed by a phylogenetic analysis, which shows that Erketu, Yunmenglong and Qiaowanlong form a clade, and are more derived than Euhelopus.  相似文献   

Biostratigraphy of the Garau Formation (Berriasian?–lower Cenomanian) in central part of Lurestan zone,northwest of Zagros,Iran     

《Cretaceous Research》2013

Deposition of organic rich black shales and dark gray argillaceous limestones in the Berriasian–Turonian interval has been documented in many parts of the world. Northwest of Zagros, Iran (Lurestan zone), thin bedded black shales and marls, dark gray argillaceous limestones and fissile limestone layers, having bitumen, of the Garau Formation are deposited. For biostratigraphic studies two stratigraphic sections including one surface section (Kuzaran) and one subsurface section (Naft well) were selected, respectively. In this study, 61 foraminiferal species belonging to 17 genera have been identified, and 12 biozones were recognized. Based on fossils distribution and biozones identification, the age of the Garau Formation is Berriasian?–early Cenomanian. In addition, the micropalaeontological study demonstrated a variety of widespread morphological changes in planktonic foraminifera assemblages (e.g., the elongation of the final chambers, appearance of twin chambers in the last whorl). These changes coincide with deposition of argillaceous limestones and marls rich in organic matter, indicating oceanic anoxic events. On this basis, three oceanic anoxic events such as OAE1a, OAE1b and OAE1d were recognized in Naft well section and two (OAE1b and OAE1d) in Kuzaran section.  相似文献   

Late Cretaceous paleoenvironmental evolution of the Tarfaya Atlantic coastal Basin,SW Morocco     

《Cretaceous Research》2013

Lithological evidence, benthic foraminiferal census counts, and X-ray fluorescence (XRF) scanner-derived elemental data were integrated with planktonic foraminiferal biostratigraphy and bulk carbonate stable isotopes to retrace the Turonian to early Campanian paleoenvironmental evolution and sea-level history of the Tarfaya Atlantic coastal basin (SW Morocco). The lower Turonian is characterized by laminated organic-rich deposits, which contain impoverished benthic foraminiferal assemblages, reflecting impingement of the oxygen minimum zone on the shelf during a sea-level highstand. This highstand level is correlated to the global transgressive pulse above the sequence boundary Tu1. The appearance of low-oxygen tolerant benthic foraminiferal assemblages dominated by Gavelinella sp. in the middle to upper Turonian indicates an improvement in bottom water oxygenation, probably linked to offshore retraction of the oxygen minimum zone during a regressive phase. This interval is marked by major regressive events expressed by a series of erosional truncations associated with the prominent sequence boundaries Tu3 and/or Tu4. Dysoxic–anoxic conditions recorded in the upper Santonian of the Tarfaya Basin coincide with the eustatic sea-level rise prior to Sa3 sequence boundary. The lower Campanian transgression, only recorded in the southern part of the Tarfaya Basin, coincided with substantial deepening, enhanced accumulation of fine-grained clay-rich hemipelagic sediments and improved oxygenation at the seafloor (highest diversity and abundance of benthic foraminiferal assemblages). Stable isotope data from bulk carbonates are tentatively correlated to the English Chalk carbon isotope reference curve, in particular the Hitch Wood Event in the upper Turonian, the Navigation Event in the lower Coniacian, the Horseshoe Bay Event in the Santonian and the Santonian/Campanian Boundary Event.  相似文献   

Charophytes from the Upper Berriasian of the Western Interior Basin of the United States     

《Cretaceous Research》2013

A charophyte flora from the Upper Berriasian is described from the Lakota (Black Hills, South Dakota) and Cedar Mountain formations (San Rafael Swell, Utah) of the Western Interior Basin, United States of America. Whereas the latter is dominated by monotonous assemblages of the clavatoracean Nodosoclavator bradleyi (Harris, 1939), found in temporary lakes within palustrine facies, the flora of the Lakota Formation consists of more varied assemblages of the clavatoraceans N. bradleyi (Harris, 1939), Clavator grovesii grovesii Harris 1939, C. bilateralis Peck 1957 and early characeans (Mesochara sp. or Tolypella sp.). This flora was found in deposits related to permanent lakes in fluvial floodplains, i.e. lacustrine marls and limestones that do not show any evidence of subaerial exposure. To date, little is known about C. bilateralis, we provide a new definition on the basis of its particular structure, which shows lateral bract-cell units with a pinnate arrangement. This species appears to be endemic to North America and stratigraphically limited to the earliest Cretaceous. C. grovesii grovesii is part of a long-lasting charophyte lineage, which until now was considered to have originated in the Central Tethyan Archipelago (Europe) during the Early Berriasian, about 145 Ma, and limited to Eurasia until most of the Early Cretaceous. The new data presented here suggest that during the Berriasian this species was very broadly distributed, comprising North America, Europe and China.  相似文献   

Reassessment of coelurosaurian (Dinosauria,Theropoda) remains from the Upper Cretaceous Wangshi Group of Shandong Province,China     

《Cretaceous Research》2013

Non-avian theropods are well represented in the Cretaceous of Asia. However, the first theropod remains ever reported from China, from the Wangshi Group of Shandong Province, have not been reassessed since they were described by Carl Wiman in 1929, despite the great strides that have been made in theropod phylogenetics in the last eight decades. The remains redescribed herein consist of four vertebrae (two cervicals, one dorsal and one caudal) from one site, and a caudal vertebra and ungual phalanx from another. The vertebrae from the first site are assigned to tyrannosauroids and ornithomimosaurs, as is the caudal vertebra from the second site, whereas the manual ungual also bears resemblances to those of non-maniraptoran coelurosaurs (specifically compsognathids and ornithomimosaurs). Theropods remain relatively rare in the Wangshi Group; nevertheless, the remains redescribed herein highlight the potential for the discovery of more theropod remains in future excavations.  相似文献   

内蒙银根-额济纳旗盆地白垩系中硅化木化石及其沉积环境     

张明震  戴霜 《地质学报》2013,87(8):1059-1066

内蒙古银根 额济纳旗盆地是我国北方重要的中－新生代陆内含油气盆地,主要出露白垩系冲洪积 河湖相碎屑岩及火山岩夹层。本文描述了在盆地东南部下白垩统巴音戈壁组下段（1号）和苏红图组二段底部（2号）发现的上、下两处原始埋藏的硅化木化石,并探讨了早白垩世时期盆地沉积时的气候环境。两处化石均保存完好,表面结构较为完整。巴音戈壁组上部和苏红图组下部泥岩段孢粉分析结果显示地层时代为早白垩世中晚期。同时,孢粉植物群揭示该时期银根 额济纳旗盆地气候环境温暖湿润,植被茂盛。根据化石保存特征和产出位置的地层岩性,初步推测1号硅化木化石点系冲洪积物快速堆积所致,2号硅化木化石点系火山喷发物瞬间埋藏所致,其埋藏时代大致为早白垩世晚期。  相似文献   

An apparent magmatic cycle in the Tasman geosyncline     

Germaine A. Joplin 《Australian Journal of Earth Sciences》2013,60(1):51-69

The igneous events of two geosynclines within the N.S.W. portion of the Tasman Orthogeosyncline are compared, not according to the actual ages of the igneous rocks, but on the basis of their position with respect to the development of the geosyncline. Thus, Cambrian volcanic rocks in one depositional area are compared with Lower Devonian in the other, Ordovician and Silurian with Middle Devonian‐Lower Carboniferous, and Devonian with Permian. Intrusive rocks are fitted into this scheme, and their ages discussed. Such a comparison reveals an apparent igneous cycle, and speculations on the cause of such a cycle are outlined.  相似文献   

The Harry Creek Deformed Zone,a retrograde schist zone of the Arunta Block,central Australia     

A. R. Allen  L. P. Black 《Australian Journal of Earth Sciences》2013,60(1-2):17-28

The Harry Creek Deformed Zone, a retrograde schist zone of epidote amphibolite facies grade, which separates the granulite facies Utralanama Block from the amphibolite facies Ankala Block in the southeastern Strangways Range, N.T., is typical of the retrograde schist zones transecting the Arunta Block. Associated with the deformed zone is a small deformed granitic pluton and its various offshoots—the Gumtree Granite Suite—which provides structural and geochrono‐logical evidence that the Harry Creek Deformed Zone has had a polyphase deforma‐tional history. Early movements within the deformed zone pre‐dated intrusion of the Gumtree Granite Suite and resulted in the movement of the Utralanama and Ankala Blocks into their present juxtaposition. Reactivation of much of the zone during the Alice Springs Orogeny brought about the schistose character of the zone and the deformation of the granitic rocks. Further minor reactivation of the zone, subsequent to the main phase of the Alice Springs Orogeny, resulted in limited development of pseudotachylytes.

The age of the granite (990 ± 13 m.y.) gives a minimum age for initiation of the zone, and evidence for the nature of the structures associated with the early movements is presented. It is suggested that the Harry Creek Deformed Zone represents a post‐orogenic wrench fault which has been reactivated. Early movements, which were of a brittle transcurrent nature, brought about major uplift (up to 10 km) to the north, and lateral movements may have been of the order of 60 km in a sinistral sense. Comparison with the Redbank Zone indicates many similarities, suggestive of a similar history.  相似文献   

The origin of the Naturaliste Plateau,SE Indian Ocean: Implications from dredged basalts     

P.J. Coleman  P.J. Michael  J.C. Mutter 《Australian Journal of Earth Sciences》2013,60(3-4):457-468

Although a 1972 dredging by USNS Eltanin from the submarine Naturaliste Plateau was reported to yield rocks of continental origin, a re‐examination of the dredge haul shows that the rock clasts are in fact altered tholeiitic basalts. They have affinities both with MOR basalts and, especially, within‐plate basalts. Petrographically they correlate most closely with the Bunbury Tholeiitic Suite on the Australian mainland to the east. The basalts are reworked cobbles in a manganiferous Quaternary slump mass, which contains a quartz‐rich, felsic, detrital mineral suite with a granite‐gneiss provenance. The basalt cobbles were part of a basal conglomerate, which covered large areas of the Plateau. It is suggested that this was laid down from nearby elevated volcanic structures formed during the inception of seafloor spreading and the separation of Greater India from Australia at about 122 Ma BP.  相似文献