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1.
In the southern Tethyan margin, the Essaouira-Agadir Basin (EAB), south of Morocco, exhibits well-exposed and fossiliferous sections of Aptian–Albian age. Biostratigraphy by ammonoids and sedimentological analysis have been realized for five sections located along an E-W transect in the EAB. The studied successions were dated from the latest Early Aptian to the Early Albian and are characterized by five major sedimentary discontinuities defining at least four main sedimentary sequences. The Late Aptian–Early Albian succession can be considered a gently westward-dipping ramp, marked by a deepening upward evolution. A quantitative study of calcareous nannofossils and calcium carbonate content has been performed on three of these sections. At this time, the EAB was located in the tropical-equatorial hot arid belt. The decrease in both calcium carbonate content and Nannoconus abundances at the Aptian–Albian transition could be the result of cooler climatic conditions recognized in the EAB, and/or of the associated increasing terrigenous input and nutrients, which hindered carbonate production. In the EAB, the nannofossil productivity is higher below the deposition of dark levels, which are coeval with the Niveau Paquier, recognized as the expression in southern France of the OAE 1b (Early Albian). During the Early Albian, the EAB was characterized by nannofossil fluxes two times lower than the upwelling-influenced Mazagan Plateau (southern Tethyan margin) and eight times lower than the Vocontian Basin (northern Tethyan margin). These results show that, with respect to the northern Tethyan margin, trophic conditions in sea surface waters of the pelagic realm of the southern Tethyan margin were lower. Comparable results obtained by Heldt et al. in the neritic realm of the southern Tethyan margin have been ascribed to more arid climatic conditions. 相似文献
2.
Sharifi MOHAMMAD Foroughi FARIBA Ghasemi-Nejad EBRAHIM Shekarifard ALI Yazdi-Moghadam MOHSEN Sarfi MEHDI 《《地质学报》英文版》2019,93(6):1885-1899
The lower Cretaceous rock units of the Koppeh-Dagh Basin of northeastern Iran were investigated here in terms of biostratigraphy, depositional setting and geochemical analyses to find out if they, alike other parts of the world, are rich in petroleum. For this purpose, a stratigraphic framework is established using calcareous nannofossil and palynological elements. A nannoplankton zonation based on which subzones of the zones CC7 – CC8 of Sissingh(1977) and their equivalent NC6 – NC8 of Roth(1978) was established indicating a Late Barremian–Albian age. Palynological assemblages led us to establish the local palynozone of Odontochitina operculata. A dominantly marginal basin to a transitional zone between shelf and basin under a dysoxic–anoxic condition with low to moderate sedimentation rates coincided with a gradual sea level rise was introduced as the environment of deposition for the strata via interpretation of the palynological parameters and quantitative palynology. The obtained data from Rock-Eval pyrolysis in compilation with palynofacies analysis reveals that the studied succession contains mainly gas-prone type III kerogen. The Spore Coloration Index(SCI) alongside with the Rock-Eval pyrolysis results(low values of HI and TOC) proves that these rock units locally produced natural gas during the time under consideration. 相似文献
3.
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
4.
N. Yu. Bragin 《Stratigraphy and Geological Correlation》2018,26(3):333-343
The assemblages of the Early Jurassic (Hettangian–Pliensbachian) and Late Jurassic–Early Cretaceous (Tithonian–Berriasian) radiolarians were described for the first time in the eastern part of the Ekonai Zone of the Koryak Highland. The Hettangian–Pliensbachian assemblage was found in siliceous rocks of the Ionai Nappe and this finding expands the stratigraphic interval of its siliceous sequences from the Carboniferous to the Early Jurassic. The Tithonian–Berriasian assemblage was found in volcanosiliceous rocks of the Yanranai accretionary complex. Both assemblages contain taxa abundant in the Tethyan regions. 相似文献
5.
The Lower Cretaceous ammonite fauna of Japan was influenced by the Tethyan, Boreal and North Pacific realms with their oceanic current patterns and ammonite distributions. The hypothesis of oceanic circulation can be utilized to interpret the existence of the “Bering Strait” and the changing position of the “Boreal front,” that is the contact region of warm and cold-water masses. To understand such a system fully, a comprehensive understanding of the geographical distribution of ammonite faunas is required. The occurrence of twenty-five ammonite species, belonging to twenty genera, is confirmed in the Barremian to Albian of Japan. Of these, 24 species are described in this paper, including Barremites macroumbilicus sp. nov. The fauna can be divided into three associations, lower, middle, and upper, indicating late Barremian, late Aptian, and late Albian of the European standard zonation. The faunal characters suggest that the habitats of these ammonite faunas may have changed during later Early Cretaceous, with faunas characterizing three different environments, i.e., nearshore, intermediate, and distal shelf to upper slope setting. Ammonites of the lower association (late Barremian) are related to those of the Tethys, Boreal European, and circum-Pacific regions, and suggest that the Early Cretaceous Katsuuragawa Basin was deposited under the influence of currents from both high latitude and equatorial areas. The occurrence of Crioceratites (Paracrioceras) suggests that the Boreal European elements, including Simbirskites and Crioceratites (Paracrioceras), transited between Northwest Europe and Japan through the Arctic Sea, indicating that the Pacific Ocean was connected with the Arctic Sea at that time. The second association (late Aptian) is composed of ammonites of the Tethyan and circum-Pacific regions. As European Boreal ammonite taxa are absent in this association, it is concluded that the Pacific Ocean probably was not connected with the Arctic Sea at the time. Consequently, the “Boreal Front,” marking the contact between warm and cold water masses, was located at mid-latitude in the “Bering Strait” region during Barremian and subsequently moved northward during Albian. The uppermost ammonite association (late Albian) also consists of Tethyan and circum-Pacific taxa. Desmoceras (Pseudouhligella) poronaicum expanded its range with northward and eastward circulation of oceanic currents, suggesting the current must have represented a warm water-mass from the equator. The species subsequently migrated from the southern Katsuuragawa Basin to the Hokkaido area during late to latest Albian. 相似文献
6.
For the first time, the calcareous nannofossils of the chalky limestone of upper Abderaz Formation and lower part of Abtalkh Formation have been studied. In this study, 83 nannoplanktonic species of 45 genera were identified and presented. A biostratigraphic study of calcareous nannofossils from this section has allowed the recognition of five calcareous nannofossil biozones of Sissingh (Geol Mijnbouw 56:37–65, 1977) CC17–CC21. On the obtained calcareous nannofossils, the age of this section is Late Santonian/Early Campanian–Early Late Campanian. 相似文献
7.
The Gurpi section in western Shiraz, faulted Zagros range of southwestern Iran, contains one of the most complete Early Santonian
to Late Maastrichtian sequences. The lack of a good fundamental paleontological study is a strong motivation for investigating
calcareous nannofossils in southwestern Iran. The Gurpi Formation is mainly made up of grey shale. As a result of this study,
23 genera and 47 species of nannofossils have been identified for the first time. This confirms the existence of biozones
CC14–CC26, which suggests the age of Early Santonian to Late Maastrichtian. All Early Santonian to Late Maastrichtian calcareous
nannofossil biozones from CC14 (equivalent to the Micula decussate Zone) to CC26 (equivalent to the Nephrolithus frequens Zone) are discussed. Additionally, the zonal subdivision of this section based on calcareous nannofossils, is correlated
with planktonic foraminiferal zones (Dicarinella asymetrica Zone to Abathomphalus mayaroensis Zone). We can also learn about the predominant conditions of the studied sedimentary basin that was in fact a part of the
Neotethys basin with the existence of index species of calcareous nannofossils indicating a warm climate and high depths of
the basin in low latitudes. 相似文献
8.
9.
塔里木北部库车前陆盆地晚白垩世和古新世的钙质超微化石组合 总被引：8，自引：3，他引：5
库车前陆盆地是中国大型油气基地之一,盆地中的白垩系及古近系为盆地油气的主要储层。对本区白垩系的时代划分和沉积环境的精确确定直接关系到对油气田的规模、储量和分布范围的正确评价。本研究在前人划分为陆相下白垩统巴什基奇克组的顶部首次发现了由10属15种组成的晚白垩世海相钙质超微化石组合Arkangelskiellacymbiformis—Quadrumgartneri。此外,在由前人定为古新统—始新统的塔拉克组下段也发现了晚白垩世Arkangel skiellacymbiformis—Quadrumgartneri组合,在该组上段发现了古新世化石Biantholithussparsus。该成果既为准确确定这两个岩组的地质时代提供了可靠的古生物证据,又为本区存在晚白垩世地层和海相沉积提供了佐证,表明巴什基奇克组顶部存在晚白垩世的海相沉积,塔拉克组下段属于上白垩统,上段属于古新统。 相似文献
10.
11.
12.
Lower Cretaceous sediments of the northwestern part of the Kopet Dagh sedimentary basin have been sampled with the purpose
to study stratigraphic distribution of calcareous nannofossils. A total of 87 samples from the 1900-m-thick marly limestones,
shales and siltstones of the Sarcheshmeh and Sanganeh Formations (late Barremian-early Aptian) displayed diverse nannofossil
assemblages. Representative species of the following genera were recorded from the Sarcheshmeh Fm.: Braarudosphaera, Calcicalathina, Calciosolenia, Chiastozygus, Conusphaera, Cretarhabdus, Cyclagelosphaera, Eprolithus, Haqius,
Hayesites, Lithraphidites, Manivitella, Micrantholithus, Nannoconus, Radiolithus, Retecapsa, Rhagodiscus, Rucinolithus, Watznaueria, and Zeugrhabdotus. In the Sanganeh Formation, Biscutum, Broinsonia, Cribrosphaerella, Crucicribrum, Cyclagellosphaera, Diazomatolithus, Discorhabdus, Eiffellithus, Lithraphidites,
Nannoconus, Prediscosphaera, Rhagodiscus, Tranolithus, and Watznaueria were found. The identified nannofossil assemblages enabled the recognition of NC5-NC7A zones in the studied part of the section.
Paleoecologically, these nannofossil assemblages are typical for the Lower Cretaceous of the Tethyan realm and indicate warm
surface water conditions. 相似文献
13.
Mohammadanvar Moheghy Fatemeh Hadavi Lida Khodadadi Marziyeh Notghi Moghaddam 《Arabian Journal of Geosciences》2014,7(10):4203-4220
By attention to the stratigraphic value of calcareous nannoplanktons for the age determination of sedimentary beds, for the first time Late Cretaceous calcareous nannofossil taxa, their distributions and relative abundances were recorded from the lower and the upper boundary of Aitamir Formation located in northeast Iran. In the present study, biostratigraphy and paleoecological conditions were reconstructed. The Aitamir Formation comprises glauconitic sandstones and olive-green shales. In this work, samples were prepared with smear slides, and nannofossils of these boundaries are listed and figured. They were photographed under a light microscope. Based on nannoplanktons and as a result of biostratigraphic studies, the age of the lower boundary of the Aitamir Formation in the east Kopet Dagh is Early/Middle Turonian, the age of the lower boundary in the west Kopet Dagh is Late Turonian/Early Coniacian, the age of the upper boundary of the Aitamir Formation in the east Kopet Dagh is Late Santonian, and the age of the upper boundary of this Formation in the west Kopet Dagh is Early Campanian. Based on paleoecological interpretation, the Aitamir Formation was deposited in a shallow marine environment, at relatively low latitude. A deepening trend of the sedimentary basin is recognized passing from Aitamir Formation to the overlying Abderaz Formation while in the lower boundary from Sanganeh to Aitamir Formation depth decreased. 相似文献
14.
Two cored boreholes in the central part of the North West German Basin recovered a unique section of Upper Barremian to Lower Aptian strata. Calcareous nannofossils show a distinctive shift from boreal endemic assemblages in the Barremian to cosmopolitan ones in the Aptian. This onset of new cosmopolitan species (e.g., Chiastozygus litterarius, Flabellites oblongus, Rhagodiscus angustus, Braarudosphaera sp., Eprolithus sp.) is spread over an interval of 25m, starting well below the early Aptian "Fischschiefer", a dark laminated shale rich in organic matter. These changes in the composition of calcareous nannofossils indicate that major palaeoceanographic changes occurred before the deposition of the Fischschiefer.The distribution pattern of calcispheres allows the differentiation of two sedimentary successions, separated by the Fischschiefer. The lower succession, which includes the sediments below the base of the Fischschiefer, indicates a boreal-pelagic environment. The lower part of the upper successions which includes the Fischschiefer, represents warmer inner shelf conditions. This corresponds to the presence of rich Tethyan-derived nannoconid assemblages and the presence of the planktonic foraminifera Hedbergella in the Fischschiefer. The topmost part of the upper succession (middle Aptian, Hedbergella marl) suggests a change to a pelagic warmer water environment. Two new taxa are introduced: the calcareous dinoflagellate cyst Obliquipithonella laqueata n. sp. and the foraminiferan Choanaella fortunate n. gen. n. sp. 相似文献
15.
Organic biomarker and nannofossil assemblages are used in combination with sedimentary petrology to identify the role of diagenesis for the formation of a rhythmic calcareous succession. A record from the Early Pliocene of the Maldives (Ocean Drilling Program, ODP Leg 115) is presented containing precession and eccentricity cycles expressed as variable aragonite content. Additional sub‐Milankovitch cycles are caused by rhythmic precipitation of calcite cement in the lower part of the interval. Comparison with palaeo‐productivity indicators (nannofossils, chlorin, total organic carbon) suggests that cementation occurs preferentially in intervals characterized by increasing or decreasing productivity. The coupled variability in productivity and carbonate diagenesis is attributed to the effect of organic matter degradation in the sediment. The observed combination of primary and diagenetic factors hampers the interpretation of the cyclicity on Milankovitch and sub‐Milankovitch scales. Diagenetically stable proxies for palaeo‐productivity, such as nannofossil assemblage data, were used to distinguish between palaeoclimate and diagenetic influences. 相似文献
16.
Damien Carcel Claude Colombié Fabienne Giraud Bernard Courtinat 《Sedimentary Geology》2010,223(3-4):334-359
Boreal and Tethyan realms of Western Europe present significant sedimentological, paleontological, and stratigraphic differences. The purpose of this study is to constrain regional versus global controls on the dynamics of a sedimentary system located at the interface of these two realms in order to better understand the origin of their differences. Detailed sedimentological, palynofacies and calcareous nannofossil analyses were performed on two sections from the La Rochelle platform (western France). The Pas section includes part of the Late Oxfordian and Early Kimmeridgian, and the Rocher d'Yves section is assigned to the Late Kimmeridgian. They correspond to monotonous marl–argillaceous limestone alternations. Limestones are essentially mudstones with echinoderms, bivalves and foraminifera that suggest low-energy, open-marine conditions. Highly bioclastic and/or peloidal deposits occur commonly, and show wackestones to wacke-pack-grainstones textures. These deposits indicate frequent high-energy events, and are interpreted as storm deposits. Marls dominate in the most proximal depositional environments, while calcareous deposits are more important in more distal environments. The Rocher d'Yves section is globally more marly than the Pas section, suggesting a more proximal setting. Palynofacies are dominated by woody particles, suggesting shallow-water, proximal depositional environments. Calcareous nannofossils are ascidian spicules, coccoliths, and schizospheres. Watznaueria britannica dominate calcareous nannofossil assemblages in the Pas section. The Rocher d'Yves assemblages are quasi-exclusively composed of Cyclagelosphaera margerelii, and indicate more proximal paleoenvironments than those of the Pas section. Different orders of depositional sequences are defined, with sequence boundaries corresponding to the most rapid relative sea-level falls. They are hierarchically stacked, and correlate, on the basis of ammonite zones, with the sequences of contemporaneous sections from Tethyan and boreal realms. The stacking pattern of these sequences suggests an orbital control on sedimentation. Small-, medium- and large-scale sequences correspond to precession (20 ky) cycles and to 100 ky and 400 ky eccentricity cycles, respectively. The elementary sequences have durations shorter than 20 ky. The Kimmeridgian was a period of global sea-level rise that ended in the Late Kimmeridgian. More proximal depositional environments in the Rocher d'Yves section (Late Kimmeridgian) than in the Pas section (Early Kimmeridgian) imply a progradation of the La Rochelle platform during the Kimmeridgian. This progradation resulted from a slowdown of the subsidence in the Aquitaine Basin during the Kimmeridgian, corresponding to the first steps of Atlantic Ocean opening. High-frequency cycles on the La Rochelle platform formed in sync with Milankovitch orbital cycles, while tectonics controlled the formation of the low-frequency cycles. 相似文献
17.
In the Bavarian Alps (Germany), west of the Isar River, the abyssal deposits of the Lower Barremian to Upper Campanian Rhenodanubian Group consist of siliciclastic and calcareous turbidites alternating with hemipelagic non-calcareous mudstones. The up to 1500-m-thick succession, deposited in the Penninic Basin to the south of the European Plate, is characterized by a low mean sedimentation rate (c. 25 mm kyr−1) over 60 million years. Palaeocurrents and turbidite facies distribution patterns suggest that sedimentation occurred on a weakly inclined abyssal plain. The highest sedimentation rates (up to 240 mm kyr−1) were associated with the calcareous mud turbidites of the newly defined Röthenbach Subgroup, which includes the Piesenkopf, Kalkgraben and Hällritz formations (Middle Coniacian to Middle Campanian). These calcareous turbidites prograded from the west, and interfinger towards the east with red hemipelagic claystone. A high sea level presumably favoured pelagic carbonate production and accumulation on the shelves and on internal platforms in the western part of the basin, whereas siliciclastic shelves with steep slope angles have bordered the eastern part of the basin, where a dearth of turbidite sedimentation and increased Cretaceous oceanic red beds deposition occurred. In contrast to the eustatically-induced Middle Coniacian to Lower Campanian Cretaceous oceanic red beds (calcareous nannoplankton zones CC14 to CC18), red hemipelagites of Early Cenomanian age (upper part of calcareous nannoplankton zone CC9) and early Late Campanian age (upper part of zone CC21 and zone CC22) are interpreted as the result of regional tectonic activity. 相似文献
18.
Tertiary Calcareous Nannofossil Biostratigraphy in the North Part of the South China Sea 总被引：1，自引：0，他引：1
The marine Tertiary sequence in the north part of the South China Sea may be divided into 18 LateOligocene to Pliocene calcareous nannofossil zones and one unnamed Eocene assemblage based on an analysisof calcareous nannofossils from 40 offshore boreholes. The unnamed Eocene assemblage has been found onlyon the northeast margin of the Zhujiangkou basin. The 18 cakareous nannofossil zones of the Late Oligoceneto Pliocene were deposited in succession, but their development degrees are different. Among the 18 calcareousnannofossil zones, those corresponding to Martini's (1971) NN4- NN5 zones, NN11 zone and NN13-NN15zones are well developed, relatively persistent laterally and also widely distributed. They are the importantmarkers for the stratigraphical subdivision and correlation of the Upper Tertiary between the various basins inthe north part of the South China Sea. Based on the calcareous nannofossils and the sedimentsry features coup-led with the foraminifer zonation in certain basins, the present paper discusses the sedimentary characteristicsof the marine Tertiary and as well as the distribution and development of the sedimentary hiatus in the region.The calcareous nannofossil markers for the Upper / Lower Tertiary and the Quaternary / Tertiary boundaries,and the characteristics and geological significance of the reworked calcareous nannofossils are also discussed inthe paper. 相似文献
19.
20.
S. V. Zyabrev 《Russian Journal of Pacific Geology》2011,5(4):313-335
The East Sakhalin accretionary wedge is a part of the Cretaceous-Paleogene accretionary system, which developed on the eastern
Asian margin in response to subduction of the Pacific oceanic plates. Its formation was related to the evolution of the Early
Cretaceous Kem-Samarga island volcanic arc and Late Cretaceous-Paleogene East Sikhote Alin continental-margin volcanic belt.
The structure, litho-, and biostratigraphy of the accretionary wedge were investigated in the central part of the East Sakhalin
Mountains along two profiles approximately 40 km long crossing the Nabil and Rymnik zones. The general structure of the examined
part of the accretionary wedge represents a system of numerous east-vergent tectonic slices. These tectonic slices. tens to
hundreds of meters thick. are composed of various siliciclastic rocks, which were formed at the convergent plate boundary,
and subordinate oceanic pelagic cherts and basalts, and hemipelagic siliceous and tuffaceous-siliceous mudstones. The siliciclastic
deposits include trench-fill mudstones and turbidites and draping sediments. The structure of the accretionary wedge was presumably
formed owing to off-scraping and tectonic underplating. The off-scraped and tectonically underplated fragments were probably
tectonically juxtaposed along out-of-sequence thrusts with draping deposits. The radiolarian fauna was used to constrain the
ages of rocks and time of the accretion episodes in different parts of the accretionary wedge. The defined radiolarian assemblages
were correlated with the radiolarian scale for the Tethyan region using the method of unitary associations. In the Nabil zone,
the age of pelagic sediments is estimated to have lasted from the Late Jurassic to Early Cretaceous (Barremian); that of hemipelagic
sediments, from the early Aptian to middle Albian; and trench-fill and draping deposits of the accretionary complex date back
to the middle-late Albian. In the Rymnik zone, the respective ages of cherts, hemipelagic sediments, and trench facies with
draping deposits have been determined as Late Jurassic to Early Cretaceous (middle Albian), middle Aptian-middle Cenomanian,
and middle-late Cenomanian. East of the rear toward the frontal parts of the accretionary wedge, stratigraphic boundaries
between sediments of different lithology become successively younger. Timing of accretion episodes is based on the age of
trench-fill and draping sediments of the accretionary wedge. The accretion occurred in a period lasting from the terminal
Aptian to the middle Albian in the western part of the Nabil zone and in the middle Cenomanian in the eastern part of the
Rymnik zone. The western part of the Nabil zone accreted synchronously with the Kiselevka-Manoma accretionary wedge located
westerward on the continent. These accretionary wedges presumably formed along a single convergent plate margin, with the
Sakhalin accretionary system located to the south of the Kiselevka-Manoma terrane in the Albian. 相似文献