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1.
A new species of nerineoid gastropod, Eunerinea mendozana, is described from the top of the Agrio Formation, Lower Cretaceous, at Lomas Bayas, Mendoza Province, west-central Argentina. The significance of this record lies in that it extends the Early Cretaceous distribution of the genus to the Southern Hemisphere and also may point to the occurrence of subtropical conditions in the northern part of the Neuquén Basin close to the Hauterivian/Barremian boundary. Individuals of E. mendozana are found forming large monospecific assemblages immersed in carbonate sediments. The relationships of E. mendozana with other South American Early Cretaceous nerineoids are considered, together with a re-evaluation of some of those records. 相似文献
2.
Early Cretaceous elasmobranchs still are very insufficiently known despite all progress that has been accomplished in recent years. Here, a small elasmobranch assemblage is presented from the Valanginian of Austria that contributes significantly to a better understanding of early Cretaceous elasmobranch diversity. The new assemblage comprises two new carcharhiniform sharks, Altusmirus triquetrus gen. et sp. nov. and Fornicatus austriacus gen. et sp. nov., a new orectolobiform shark, Similiteroscyllium iniquus gen. et sp. nov., and a galeomorph shark tooth of uncertain affinities. The recent identification of Similiteroscyllium gen. nov. has shown that it has strong similarities with Ornatoscyllium rugasimulatum from the Lower Cretaceous of France. Significant differences of the tooth morphology of O. rugasimulatum and the type specimen O. freemani justify full reconsideration of the systematic position of O. rugasimulatum and require it to be reassigned to Similiteroscyllium gen. nov. described in this paper. The new assemblage described here, and those from the Valanginian of France and Poland comprising 30 additional taxa, indicates that Early Cretaceous elasmobranch diversity was significantly higher than previously assumed. Consequently, the supposed diversity decline of elasmobranchs across the Jurassic-Cretaceous boundary represents a collecting bias rather than a real pattern. 相似文献
3.
A new species of Elcanidae (Orthoptera: Elcanoidea), Panorpidium yixianensis sp. nov., is described based on two new specimens from the Lower Cretaceous Yixian Formation of northeastern China. It differs from other species in forewing characters and spines on the hind tibiae. In addition, a new specimen Burmelcana sp., is described and figured based on an amber inclusion from the mid-Cretaceous Burmese (Myanmar) amber. P. yixianensis sp. nov. represents the first definite record of Elcanidae in the Early Cretaceous Jehol biota, and Panorpidium is the only genus of Ensifera to be found in the Early Cretaceous faunas of England, Russia and China. 相似文献
4.
Tianyi Shen Yue Chen Guocan Wang Junliang Ji Yong Wang Pan Zhang Paul Sotiriou Rong Guo Zezhuang Xu 《地学学报》2020,32(2):166-178
Analysing the provenance changes of synorogenic sediments in the Turpan‐Hami basin by detrital zircon geochronology is an efficient tool to examine the uplift and erosion history of the easternmost Tian Shan. We present detrital zircon U‐Pb analysis from nine samples that were collected within marginal lacustrine Middle‐Late Jurassic and aeolian‐fluvial Early Cretaceous strata in the basin. Middle‐Early Jurassic (159–172 Ma) zircons deriving from the southern Junggar dominated the Middle Jurassic sample from the western Turpan‐Hami basin, whereas Permian‐Carboniferous (270–330 Ma) zircons from the Bogda mountains were dominant in the Late Jurassic to Early Cretaceous samples. Devonian‐Silurian (400–420 Ma) and Triassic (235–259 Ma) zircons from the Jueluotage and Harlik mountains constituted the subordinate age groups in the Late Jurassic and Early Cretaceous samples from the eastern basin respectively. These provenance transitions provide evidence for uplift of the Bogda mountains in the Late Jurassic and the Harlik mountains since the Early Cretaceous. 相似文献
5.
Two new Early Cretaceous fossil rove beetle species, Paleosiagonium brevelytratum n. gen. n. sp. and Paleosiagonium adaequatum n. gen. n. sp. are described from the Lower Cretaceous Yixian Formation of Liaoning Province, China. They are clearly placed in the extant Piestinae according to the following characters: body elongate and flat; anterior coxae small and globose; abdomen long and parallel-sided, with six visible sterna and one pair of paratergites on segments III–VII. This is the first report on the occurrence of the coleopteran subfamily Piestinae in the fossil record. The new discoveries indicate that Piestinae have originated at least by the Early Cretaceous, at about 125–120 Ma. 相似文献
6.
Denudation history of the Bocaina Plateau, Serra do Mar, southeastern Brazil: Relationships to Gondwana breakup and passive margin development 总被引：1，自引：0，他引：1
Silvio T. Hiruma Claudio Riccomini May C. Modenesi-Gauttieri Peter C. Hackspacher Julio C. Hadler Neto Ana O.B. Franco-Magalhes 《Gondwana Research》2010,18(4):674-687
The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 ± 32 and 46 ± 5 Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 ± 1.51 to 11.1 ± 1.48 μm, with standard deviations between 1.16 and 1.83 μm. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (> 200 Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Paraná, Bauru, and Santos basins. 相似文献
7.
The Upper Cretaceous sedimentary sequence at International Ocean Discovery Program Site U1512 in the Ceduna Sub-basin of the Great Australian Bight represents a continuous, > 690 m thick interval of black silty clay and claystone spanning the lower Turonian through Lower Campanian (~10 million years). Sediments were deposited in an elongate, ~E-W oriented, ~2500 km long rift system that developed between Australia and Antarctica with an open-ocean connection to the west and a continental bridge to the east. Site U1512 cores provide a unique, continuous record of Late Cretaceous deposition in the Ceduna Sub-basin on the hanging wall of the Wallaroo Fault Zone. Study of U1512 samples could provide both an important high-latitude, southern hemisphere perspective on climatic evolution during the peak and demise of the Cretaceous hothouse and an offshore record of the sedimentation history in the basin during the Late Cretaceous portion of the Gondwanan breakup.The Upper Cretaceous sequence at Site U1512 is notable for its lithologic uniformity. Burrow-mottled to massive claystone and silty claystone make up the majority of the almost 700 m section, while rare (n = 28) isolated, 2 to 21 cm thick medium to fine sandstone beds are a minor lithology. Macrofossils present include common inoceramids and rare occurrences of other bivalves and ammonites. Microfossils include common occurrences of calcareous nannofossils, agglutinated and calcareous benthic foraminifera, radiolaria and organic-walled dinoflagellate cysts as well as rare, small, surface dwelling planktonic foraminifera. Carbonate (<7%) and organic carbon (<1.5%) contents are low. Despite the lithologic uniformity, rhythmic alternations in the intensity of magnetic susceptibility and natural gamma radiation are well-resolved in much of the recovered section and continue through minor coring gaps (as documented by downhole logs). Data from Site U1512 provide new perspectives on the deep-water frontier region between Antarctica and Australia. 相似文献
8.
David Selby 《Cretaceous Research》2009,30(5):1263-1267
A new U-Pb zircon age for the Aptian/Albian boundary (113.1 ± 0.3 Ma) indicates that an alternate Early Cretaceous timescale that is largely devised using the K-Ar date for GL-O glauconite international standard and other K-Ar glauconite geochronology, is inaccurate. Both 40Ar/39Ar sandine and U-Pb zircon ages indicate that the K-Ar date for the GL-O international standard does not record the timing of sediment deposition and thus should not be used for timescale calibration. This issue is not solely constrained to the Early Cretaceous, because other geological time intervals also reveal younger K-Ar glauconite ages in comparison to other radioisotopic dating techniques (e.g., U-Pb, Ar-Ar, Re-Os). 相似文献
9.
We reconstruct the history of denudation and landscape evolution of the northern East- Brazilian continental margin using apatite fission-track thermochronology and thermal history modeling. This part of the Brazilian Atlantic margin is morphologically characterized by inland and coastal plateaus surrounding a wide low-lying inland region, the Sertaneja Depression. The apatite fission track ages and mean track lengths vary from 39 ± 4 to 350 ± 57 Ma and from 10.0 ± 0.3 to 14.2 ± 0.2 μm, respectively, implying a protracted history of spatially variable denudation since the Permian at relatively low rates (<50 m My−1). The Sertaneja Depression and inland plateaus record Permian-Early Jurassic (300–180 Ma) denudation that precedes rifting of the margin by > 60 Myrs. In contrast, the coastal regions record up to 2.5 km of Late Jurassic-Early Cretaceous (150–120 Ma) denudation, coeval with rifting of the margin. The samples from elevated coastal regions, the Borborema Plateau and the Mantiqueira Range, record cooling from temperatures above 120 °C since the Late Cretaceous extending to the Cenozoic. We interpret this denudation as related to post-rift uplift of these parts of the margin, possibly resulting from compressional stresses transmitted from the Andes and/or magmatism at that time. Several samples from these areas also record accelerated Neogene (<30 Ma) cooling, which may record landscape response to a change from a tropical to a more erosive semi-arid climate during this time. The inferred denudation history is consistent with the offshore sedimentary record, but not with evolutionary scenarios inferred from the recognition of “planation surfaces” on the margin. The denudation history of the northeastern Brazilian margin implies a control of pre-, syn- and post-rift tectonic and climatic events on landscape evolution. 相似文献
10.
Mostafa Oukassou Omar Saddiqi Jocelyn Barbarand Samira Sebti Lahssen Baidder André Michard 《地学学报》2013,25(2):151-159
The origin of the Anti‐Atlas relief is one of the currently debated issues of Moroccan geology. To constrain the post‐Variscan evolution of the Central Anti‐Atlas, we collected nine samples from the Precambrian basement of the Bou Azzer‐El Graara inlier for zircon and apatite fission‐track thermochronology. Zircon ages cluster between 340 ± 20 and 306 ± 20 Ma, whereas apatite ages range from 171 ± 7 Ma to 133 ± 5 Ma. Zircon ages reflect the thermal effect of the Variscan orogeny (tectonic thickening of the ca. 7 km‐thick Paleozoic series), likely enhanced by fluid advection. Apatite ages record a complex Mesozoic–Cenozoic exhumation history. Track length modelling yields evidence that, (i) the Precambrian basement was still buried at ca. 5 km depth by Permian times, (ii) the Central Anti‐Atlas was subjected to (erosional) exhumation during the Triassic‐Early Cretaceous, then buried beneath ca. 1.5 km‐thick Cretaceous‐Paleogene deposits, (iii) final exhumation took place during the Neogene, contemporaneously with that of the High Atlas. 相似文献
11.
This study documents sediment infill features and their responses to the tectonic evolution of the Sichuan Basin and adjacent areas. The data include a comparison of field outcrops, well drillings, inter-well correlations, seismic data, isopach maps, and the spatial evolution of sedimentary facies. We divided the evolutionary history of the Sichuan Cretaceous Basin into three stages based on the following tectonic subsidence curves: the early Early Cretaceous (145–125 Ma), late Early Cretaceous to early Late Cretaceous (125–89.8 Ma), and late Late Cretaceous (89.8–66 Ma). The basin underwent NW–SE compression with northwestward shortening in the early Early Cretaceous and was dominated by alluvial fans and fluviolacustrine sedimentary systems. The central and northern areas of the Sichuan Basin were rapidly uplifted during the late Early Cretaceous to early Late Cretaceous with southwestward tilting, which resulted in the formation of a depression, exhibited southwestward compression, and was characterized by aeolian desert and fluviolacustrine deposits. The tectonic framework is controlled by the inherited basement structure and the formation of NE mountains, which not only affected the clastic supply of the sedimentary basin but also blocked warm-wet currents from the southeast, which changed the climatic conditions in the late Late Cretaceous. The formation and evolution of Cretaceous sedimentary basins are closely related to synchronous subtle far-field tectonism and changes in climate and drainage systems. According to the analysis of the migration of the Cretaceous sedimentation centers, different basin structures formed during different periods, including periods of peripheral mountain asynchronous thrusting and regional differential uplift. Thus, the Sichuan Cretaceous sedimentary basin is recognized as a superimposed foreland basin. 相似文献
12.
Martin Wipf Ulrich Anton Glasmacher Daniel Fritz Stockli Axel Emmerich Thilo Bechstädt Heinrich Baur 《International Journal of Earth Sciences》2010,99(3):675-686
Miocene Intrusives and Lower Cretaceous siliciclastic sedimentary rocks from the Basal Complex in western-Fuerteventura were
analyzed with low-temperature thermochronometric methods such as fission-track, and (U–Th–Sm)/He dating, in order to reveal
the evolution of the island’s exhumation history. The obtained thermochronometric data yields a very slow rate of cooling
in the order of 1.5–3°C/Myr from ~50 to 20 Ma for the Early Cretaceous siliciclastic rocks. These sedimentary units have never
been heated significantly above 240°C after deposition and still record the submarine onset of the island’s formation in the
Eocene. Intrusive bodies associated with the early Miocene magmatic activity of the central volcanic complex of the island
show rapid initial cooling rates of 50–70°C/Myr from ~20 to 14 Ma. Contemporaneous with the intrusions the cooling rate of
the Cretaceous sedimentary units increased to 25–35°C/Myr and it is inferred that this increase is associated with enhanced
uplift and erosion of the Central Volcanic Complex. After ~14 Ma rates slowed down to 3–6°C/Myr. Palaeosols overlying the
sedimentary units are themselves covered by Pliocene basalt flows and reveal that the sedimentary rocks reached the surface
before ~5 Ma. The thermochronometric data obtained in this study for central Fuerteventura is difficult to reconcile with
the cooling history derived from previously obtained fission-track and K–Ar data from the north-western part of the island.
This inconsistency is likely to indicate that the exhumation history of Fuerteventura is more complex and regionally subdivided
than previously believed. 相似文献
13.
Omkar Verma Guntupalli V.R. PrasadAnjali Goswami Varun Parmar 《Cretaceous Research》2012,33(1):183-188
Although a very high invertebrate faunal diversity is known from the outcrops of the Ariyalur group in the Cauvery Basin, southern India, little is known about its vertebrate fauna. Recent fieldwork in the badland exposures of the Karai Formation (Upper Cenomanian-Lower Turonian) near Garudamangalam in the basin has yielded two teeth belonging to the Late Cretaceous shark Ptychodus decurrens (Ptychodontidae). The fossil record of Ptychodus decurrens from the southern continents is very poor, being known from a single Late/Middle Albian occurrence in Australia. This finding documents the first record of fossil P. decurrens in India and second from a Gondwanan landmass, and provides the first evidence of a cosmopolitan, Pangaean, distribution of the species during the Albian-Turonian and additional insights into the palaeoecology of the Cauvery Basin during the deposition of the Karai Formation. 相似文献
14.
15.
《Earth》2009,92(1-4):27-76
In this study we reconstruct the evolution of the northern New England passive margin whose development has been influenced by Pleistocene glaciations. The morphology of the northern New England shelf is rather unique consisting of a inner lowland, the Gulf of Maine, with an average depth of 150 m and an area of 90,700 km2 and Georges Bank, a high whose crest is less than 40 m deep and has an area of 27,000 km2. The bank's northern slope, facing the Gulf of Maine, has a maximum relief of 377 m. On the seaward side of Georges Bank is the 2000 m high continental slope deeply cut by canyons. Two channels, Northeast and Great South Channels, east and west of Georges Bank, provide passageways from the Gulf of Maine to the open sea. This morphology was acquired by a combination of Tertiary fluvial erosion, Pleistocene glacial erosion/deposition and Pleistocene/Holocene marine processes. Fluvial/glacial erosion in the Gulf of Maine was so extensive as to expose basement, thus making it possible to map the various terranes making up this foundation. These terranes include the pre-Carboniferous Avalon and Meguma units, a Carboniferous–Permian rift basin formed by the oblique continental collision during the closure of the Paleozoic proto-Atlantic and a Late Triassic–Early Jurassic rift system created during the opening of the present Atlantic. Basement in the Gulf of Maine remained above sea level from the opening of the Atlantic 190 Ma (Early Jurassic) to the Eocene 55 Ma. That the Gulf of Maine remained a high for so long may have been due to igneous activity along the northwest-trending Boston–Ottawa Lineation extending from the vicinity of the St. Lawrence River, Canada to Gulf of Maine from Late Triassic to Early Cretaceous. The northwest-trending New England Seamounts south of Georges Bank may represent a seaward extension of this lineation. On Georges Bank, rising hundreds of meters above the Gulf of Maine, the basement exposed in the gulf is mantled by sediments thousands of meters thick. Included in these sediments are Early Jurassic- to earliest Cretaceous reefs along the continental slope and carbonates north of the reefs grading landward into continental sediments, Cretaceous–Cenozoic continental/marine terrigenous sediments and Pleistocene glacial deposits. The continental slope on the seaward flank of Georges Bank has a complex history of early to mid Mesozoic carbonate accretion, mid to late Mesozoic and Cenozoic calcareous/terrigenous sediments and canyon erosion, burial and exhumation going back to Early Cretaceous. 相似文献
16.
Teeth of a new species of hybodont shark Vectiselachos (Chondrichthyes: Lonchidiidae) are described from the late Aptian (Early Cretaceous) of southern England. Vectiselachos gosslingi sp. nov. has very distinctive coarse striations that form raised ridges over the occlusal surfaces of the crown. 相似文献
17.
A new teleosaurid from the Lower Cretaceous of Tataouine (Tunisia), Machimosaurus rex sp. nov., definitively falsifies that these crocodylomorphs faced extinction at the end of the Jurassic. Phylogenetic analysis supports its placement closer to M. hugii and M. mosae than M. buffetauti. With the skull length up to 160 cm and an estimated body length of 10 m, M. rex results the largest known thalattosuchian, and the largest known crocodylomorph at its time. This giant thallatosuchian probably was an ambush predator in the lagoonal environments that characterized the Tethyan margin of Africa during the earliest Cretaceous. Whether the Jurassic-Cretaceous mass extinction was real or artefact is debated. The discovery of M. rex supports that the end-Jurassic crisis affected primarily Laurasian biota and its purported magnitude is most likely biased by the incomplete Gondwanan fossil record. The faunal turnovers during the J-K transition are likely interpreted as local extinction events, triggered by regional ecological factors, and survival of widely-distributed and eurytypic forms by means of habitat tracking. 相似文献
18.
Mesozoic and Cenozoic thermal history of the Western Reguibat Shield (West African Craton) 
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下载免费PDF全文 Using low‐temperature thermochronology on apatite and zircon crystals, we show that the western Reguibat Shield, located in the northern part of the West African Craton, experienced significant cooling and heating events between Jurassic and present times. The obtained apatite fission track ages range between 49 and 102 Ma with mean track lengths varying between 11.6 and 13.3 μm and Dpar values between 1.69 and 3.08 μm. Zircon fission track analysis yielded two ages of 159 and 118 Ma. Apatite (U–Th)/He uncorrected single‐grain ages range between 76 and 95 Ma. Thermal inverse modelling indicates that the Reguibat Shield was exhumed during the Early Cretaceous, Late Cretaceous, Palaeocene–Eocene and Quaternary. These exhumation events were coeval with regional tectonic and geodynamic events, and were probably driven by a combined effect of plate tectonics and mantle dynamics. 相似文献
19.
《Gondwana Research》2011,19(4):674-687
The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 ± 32 and 46 ± 5 Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 ± 1.51 to 11.1 ± 1.48 μm, with standard deviations between 1.16 and 1.83 μm. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (> 200 Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Paraná, Bauru, and Santos basins. 相似文献
20.
剥蚀厚度恢复是进行盆地埋藏史、热演化史、油气成藏等定量分析的基础。文中利用镜质体反射率法、流体包裹体法、声波时差法和地层厚度趋势法等多种方法,恢复了内蒙古雅布赖盆地侏罗系和白垩系剥蚀厚度。计算结果表明,侏罗系和白垩系总剥蚀厚度为1610.9~2177.0,m;在流体包裹体法和地层厚度趋势法约束下,恢复的侏罗系剥蚀厚度为930.2~1395.3,m,白垩系剥蚀厚度为0~612.1,m。雅布赖盆地侏罗系剥蚀厚度“北大南小”,白垩系剥蚀厚度“南大北小”,反映盆地改造强度具有晚侏罗世南弱北强、早白垩世南强北弱的特征。大规模隆升剥蚀,导致地层温度下降、烃源岩遭到破坏,一定程度上制约着雅布赖盆地的烃源岩成熟演化以及油气生成。 相似文献