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1.
This study of the upper Maastrichtian to Danian sedimentary succession from the northern part of the Romanian Eastern Carpathians (Varniţa section) aims to establish an integrated biostratigraphy based on calcareous nannofossils, organic-walled dinoflagellate cysts (dinocysts) and foraminiferal assemblages, and to reconstruct the depositional environments of the interval. The stratigraphic record across the studied section is incomplete, considering that an approximately 16 m thick strata interval from the top of the Maastrichtian to lowermost Danian cannot be analyzed due to a landslide covering the outcrop. The upper Maastrichtian is marked by a succession of biostratigraphic events, such as the First Appearance Datum (FAD) of the nannoplankton taxon Nephrolithus frequens and FAD of the dinocyst species Deflandrea galeata and Disphaerogena carposphaeropsis, and the Last Appearance Datum (LAD) of Isabelidinium cooksoniae in the lower part of the section. These bioevents are followed by the LAD of the Dinogymnium spp. and Palynodinium grallator dinocyst markers in the top of the Maastrichtian deposits analyzed. In terms of foraminiferal biostratigraphy, the upper Maastrichtian Abathomphalus mayaroensis Zone is documented in the lower part of the studied section. Some bioevents, such as the bloom of the calcareous dinoflagellate genus Thoracosphaera and the FAD of the organic-walled dinocysts Damassadinium californicum, Senoniasphaera inornata, Xenicodinium lubricum and X. reticulatum suggest an early Danian age for the middle part of the section. From the Danian deposits in the Varniţa section, we describe a new organic-walled dinocyst species, Pentadinium darmirae sp. nov., which is until now the only species of the Pentadinium genus discovered in the Paleocene. The occurrence of the global Danian dinocyst marker Senoniasphaera inornata in the top of the section, suggests an age not younger than middle Danian (62.6 Ma) for the analyzed deposits.The palynofacies constituents, as well as the agglutinated foraminiferal morphogroups, used to reconstruct the depositional environments, show that the late Maastrichtian sediments were deposited in an outer shelf to distal (bathyal) environment, followed by a marine transgression during the Danian.  相似文献   

2.
Ostracode assemblages of the Poty quarry, Pernambuco-Paraíba Basin, northeastern Brazil, record an abrupt faunal change near the Cretaceous-Paleogene (K-Pg) boundary. Paleoecological and stable isotope analyses of ostracode carapaces were used to interpret the paleoenvironmental changes that took place from the Late Maastrichtian to the Early Danian. Ostracode distribution demonstrates substantial changes at and around the boundary with the last occurrences of most species and appearance of new ones. Stable isotope analyses carried out for four ostracode species distributed along the entire succession exhibit oscillations in the isotopic composition before the K-Pg boundary, thus suggesting that environmental changes may have begun slightly prior the boundary event itself. These changes may have triggered the extinctions that culminated at the K-Pg boundary, marked by positive δ18O and negative δ13C excursions. The K-Pg boundary is marked by cooling of bottom seawaters and a decrease in productivity, as well as the beginning of an extensive marine regression.  相似文献   

3.
The stratigraphy, sedimentology and syn-depositional tectonic events (SdTEs) of the Upper Cretaceous/Paleogene (K–P) succession at four localities in north Eastern Desert (NED) of Egypt have been studied. These localities are distributed from south-southwest to north-northeast at Gebel Millaha, at North Wadi Qena, at Wadi El Dakhal, and at Saint Paul Monastery. Lithostratigraphically, four rock units have been recorded: Sudr Formation (Campanian–Maastrichtian); Dakhla Formation (Danian–Selandian); Tarawan Formation (Selandian–Thanetian) and Esna Formation (Thanetian–Ypresian). These rock units are not completely represented all over the study area because some of them are absent at certain sites and others have variable thicknesses. Biostratigrapgically, 18 planktonic foraminiferal zones have been recorded. These are in stratigraphic order: Globotruncana ventricosa Zone (Campanian); Gansserina gansseri, Contusotruncana contusa, Recimguembelina fructicosa, Pseudohastigerina hariaensis, Pseudohastigerina palpebra and Plummerita hantkenenoides zones (Maastrichtian); Praemurica incostans, Praemurica uncinata, Morozovella angulata and Praemurica carinata/Igorina albeari zones (Danian); Igorina albeari, Globanomanlina pseudomenradii/Parasubbotina variospira, Acarinina subsphaerica, Acarinina soldadoensis/Globanomanlina pseudomenardii and Morozovella velascoensis zones (Selandian/Thantian); and Acarinina sibaiyaensis, Pseudohastigerina wilcoxensis/Morozovella velascoensis zones (earliest Ypresian). Sedimentologically, four sedimentary facies belts forming southwest gently-dipping slope to basin transect have been detected. They include tidal flats, outer shelf, slumped continental slope and open marine hemipelagic facies. This transect can be subdivided into a stable basin plain plus outer shelf in the extreme southwestern parts; and an unstable slope shelf platform in the northeastern parts. The unstable slope shelf platform is characterized by open marine hemipelagic, fine-grained limestones and fine siliciclastic shales (Sudr, Dakhla, Tarawan and Esna formations). The northeastern parts are marked by little contents of planktonic foraminifera and dolomitized, slumped carbonates, intercalated with basinal facies. Tectonically, four remarkable syn-depositional tectonic events (SdTEs) controlled the evolution of the studied succession. These events took place strongly within the Campanian–Ypresian time interval and were still active till Late Eocene. These events took place at: the Santonian/Campanian (S/C) boundary; the Campanian/Maastrichtian (C/M) boundary; the Cretaceous/Paleogene (K/P) boundary; and the Middle Paleocene–Early Eocene interval. These tectonic events are four pronounced phases in the tectonic history of the Syrian Arc System (SAS), the collision of the Afro-Arabian and Eurasian plates as well as the closure of the Tethys Sea.  相似文献   

4.
In the Izeh section (Zagros Basin, SW Iran), about two third of the planktonic foraminiferal species, representing less than 20% of the individuals, present in the Maastrichtian polytaxic assemblages, became suddenly extinct at the K/Pg boundary. This mass species extinction testifies end-Cretaceous catastrophic bioevent. The Cretaceous species remain became apparently extinct gradually during the earliest Danian. In fact the unkeeled globotruncanids (Globotruncanella and Rugoglobigerina) as well as the small heterohelicids (Heterohelix and Pseudoguembelina) were also affected by extinction and they were reworked in the basal Danian. Except guembelitriids which persisted longer time. The sudden species extinctions were selective, eliminating geographically restricted large, complex, and deeper dwelling forms (i.e., globotruncanids and large heterohelicids). Contrary, few cosmopolitan small, simple surface-subsurface dwellers (i.e., guembelitriids among small heterohelicids and hedbergellids) crossed the K/Pg boundary and survived the catastrophic event. This selective bioevent is related to the end-Cretaceous bolide and produced ejecta impact inducing major environmental changes as decrease in temperature, collapse of nutriment, and flow breakdown in the water mass stratification. Our geochemical results (δ13C negative shift, δ 18O positive shift, and trace elements anomalies) are consistent with the cooling due to the collision winter triggering collapse of nutriment. Especially the δ 18O values across the upper Maastrichtian and the K-Pg transition in Izeh section although they are lower; they report similar fluctuations to those in El Kef section. Thus these lower values may be indicative of somewhat warmer water at the sea floor. Besides, like as elsewhere, in Izeh, this Cretaceous end catastrophic bioevent is followed by a delayed gradual recovery. Thus, immediately after the K/Pg boundary was created a nearly empty niche in which persisted few Cretaceous survivors with dwarf individuals. These survivors despite they suffered very stressful environmental conditions, they constituted the root stock of globigerinids from which the Cenozoic planktonic foraminiferal species evolved and developed carnivorous food diet.  相似文献   

5.
An integrated study of palynology, Mössbauer spectroscopy, mineralogy and osmium isotopes has led to the detection of the first K-Pg boundary clay layer in a Southern Hemisphere terrestrial setting. The K-Pg boundary layer was independently identified at centimetre resolution by all the above mentioned methods at the marine K-Pg boundary site of mid-Waipara and the terrestrial site of Compressor Creek (Greymouth coal field), New Zealand. Mössbauer spectroscopy shows an anomaly of Fe-containing particles in both K-Pg boundary sections: jarosite at mid-Waipara and goethite at Compressor Creek. This anomaly coincides with a turnover in vegetation indicated by an interval dominated by fern spores and extinction of key pollen species in both sections. In addition to the terrestrial floristic changes, the mid-Waipara section reveals a turnover in the dinoflagellate assemblages and the appearance of global earliest Danian index species. Geochemical data reveal relatively small iridium enrichments in the boundary layers of 321 pg/g at mid-Waipara and 176 pg/g at Compressor Creek. Unradiogenic 187Os/188Os values of the boundary clay reveal the presence of a significant extraterrestrial component. We interpret the accumulation of Fe nano-phases at the boundary as originating from both the impactor and the crystalline basement target rock. The goethite and jarosite are interpreted as secondary phases formed by weathering and diagenesis. The primary phases were probably controlled by the initial composition of the vapor plume and condensation kinetics rather than condensation thermodynamics. This investigation indicates that identification of Fe in nano-phases by Mössbauer spectroscopy is an accurate and cost-effective method for identifying impact event horizons and it efficiently complements widely used biostratigraphic and geochemical methods.  相似文献   

6.
The Upper Cretaceous succession outcropping in the Anamas–Akseki Autochton, consists of approximately 500 m thick purely platform carbonate sediments. It begins with Cenomanian limestones intercalated with limestone breccias (Unit-1) containing mainly Pseudorhapydionina dubia, Pseudonummoloculina heimi, Spiroloculina cretacea (Assemblage I) and unconformably overlies the Lower Cretaceous (Barremian–Aptian) limestones with Vercorsella laurentii, Praechrysalidina infracretacea and Salpingoporella hasi. The Cenomanian limestones include foraminiferal packstone–wackestone, peloidal packstone–wackestone and mudstone microfacies deposited in restricted platform conditions. The Cenomanian succession is truncated by an unconformity characterised by locale bauxite deposits. Immediately above the unconformable surface, dolomitic limestones and rudistid limestones (Unit-2) are assigned to the upper Campanian based on the benthic foraminiferal assemblage (Assemblage II) comprising mainly Murciella gr. cuvillieri, Pseudocyclammina sphaeroidea, Accordiella conica, Scandonea samnitica and Fleuryana adriatica (smaller-sized populations). The upper Campanian limestones composed of dominantly foraminiferal-microbial packstone–wackestone microfacies deposited in shallow water environment with low energy, restricted circulation. The following limestones of the Unit-2 is characterised by sporadic intercalation of “open shelf” Orbitoides, Omphalocyclus, Siderolites assemblage (Assemblage III), assigned to the Maastrichtian, in addition to pre-existing “restricted platform” species. In the upper part of this biozone, the Rhapydionina liburnica/Fleuryana adriatica concurrent range subzone (Assemblage IIIb) is distinguished by the presence of Valvulina aff. triangularis, Loftusia minor as well as the nominal species. The Maastrichtian limestones with sporadically open marine influence consist of bioclastic (rudist-bearing) packstone–floatstone, foraminiferal packstone–wackestone with rudist fragments and peloidal/intraclastic packstone–wackestone microfacies deposited in shallow subtidal–subtidal (lagoonal) environments. The Upper Cretaceous succession passes upwardly into 70 m thick limestones and clayey limestones (Unit-3) which do not contain rudists and pre-existing foraminiferal assemblage with one exception Valvulina aff. triangularis. Variable amounts of ostracoda, discorbids, miliolids, dasycladacean algae and Stomatorbina sp. (Assemblage IV) occur into mud-rich microfacies suggesting restricted conditions with low water energy. A probable Danian age is proposed for the Unit-3 based on the occurrence of Valvulina aff. triangularis and Stomatorbina sp. which were previously recorded from Danian of peri-Tethyan platforms.  相似文献   

7.
Seven planktic foraminiferal zones are distinguished in the Maastrichtian-Paleocene succession at the north Farafra Oasis. These are the Rugoglobigerina hexacamerata (CF8b), Gansserina gansseri, and Contusotruncana contusa zones in the Maastrichtian topped by a well-known unconformity across the Cretaceous/Paleogene (K/Pg) boundary. The Danian is subdivided into two biozones: Globanomalina compressa/Praemurica inconstans-Praemurica uncinata Subzone (P1c) and Praemurica uncinata–Morozovella angulata (P2) Zone. The Late Paleocene is divided into two zones: Morozovella angulata-Globanomalina pseudomenardii (P3) and Globanomalina pseudomenardii (P4). A minor hiatus between the Danian/Selandian and Selandian/Thanetian boundaries are also recorded. These time gaps across the stage boundaries may be related to the tectonic events that affected the sedimentation regime throughout the Upper Cretaceous–Lower Paleogene interval in the Farafra Oasis.  相似文献   

8.
Calcareous nannoplankton biostratigraphy has been performed on five sedimentary sections through the marine Akveren Formation from the Bartin region of northern Turkey, on the southern Black Sea coast. This new biostratigraphy provides an age for the formation of the Early Campanian (nannofossil zone UC15aTP) to Early Selandian (nannofossil zone NP5), and highlights the presence of the Campanian/Maastrichtian, Cretaceous/Tertiary (K/T), and Danian/Selandian boundaries in this intermediate palaeolatitude location. Micula murus was identified below the K/T boundary, but Micula prinsii and Nephrolithus frequens were not, which implies that the K/T boundary interval is not complete in the study area. These dates are in agreement with previous micropaleontological studies.  相似文献   

9.
Benthic foraminifers from borehole sections recovered by drilling in the Yamal Peninsula, West Siberia, characterize the Ceratobulimina cretacea Beds (the upper Campanian-lower Maastrichtian) and the Spiroplectammina variabilis-Gaudryina rugosa spinulosa and Spiroplectammina kasanzevi-Bulimina rosenkrantzi regional zones of the lower and upper Maastrichtian, respectively. The Danian Stage is missing from the sections, which include marine deposits of the Selandian Stage attributed to the Ceratolamarckina tuberculata Beds. Foraminiferal assemblages of the beds include the Siberian endemic species associated with Paleocene foraminifers of the Midway-type fauna of subglobal distribution range. Occurrence of the latter suggests that warm-water surface currents from the North Atlantic reached southern areas of the Kara Sea.  相似文献   

10.
Although the European dinosaur succession during the latest Cretaceous and its relationship with the Cretaceous-Paleogene (K-Pg) mass extinction has been the focus of recent work, other continental vertebrates, such as crocodylomorphs, have received less attention. The European continental record of crocodylomorphs in general, and of eusuchians in particular, is relatively dense through the Maastrichtian until the K-Pg boundary. Traditionally it has been argued that continental crocodylomorphs were minimally impacted by the K-Pg extinction, but they were substantially affected in Europe with the disappearance of endemic eusuchians such as Hylaeochampsidae, Allodaposuchus and their close relatives, and non-eusuchians such as Doratodon or Theriosuchus. Despite extensive sampling in Danian continental deposits, only scarce fragmentary crocodylomorph remains have been cited. It is not until the late Paleocene and Eocene that a recovery in continental crocodylomorphs is observed. The presence of taxa such as planocraniids, the alligatoroids Diplocynodon and Hassiacosuchus, and stem crocodyloids during this period provide the first reliable continental records of Crocodylia in Europe and is best explained by post-extinction immigration from Asia or North America. By contrast, marine forms such as Thoracosaurus are found on both sides of the K-Pg boundary in Europe. The adaptation of these marine animals to different environments, from shallow seas to more transitional or fluvial environments, could be the key to their success and survival across the K-Pg boundary, as seen in other marine crocodylomorph clades such as Dyrosauridae.  相似文献   

11.
Postcranial material of a crocodylomorph from the Danian of Oulad Abdoun Basin (Morocco) is described. Several characters, in particular the shape of its dorsal osteoderms, allows its attribution to Pholidosauridae. Up till now, the latest known pholidosaurid was Terminonaris, from the Early Turonian of North America, so, the Moroccan pholidosaurid extends the stratigraphic range of the group to more than 20 million years younger, and shows that the pholidosaurids survived the K-Pg crisis. The reevaluation and the phylogenetic analysis of Dakotasuchus kingi, Woodbinesuchus byersmauricei, and Sabinosuchus coahuilensis, previously considered as goniopholidids and dyrosaurid, respectively, revealed rather that they are pholidosaurids. This analysis also suggests that at least two independent pholidosaurid lineages reached the Maastrichtian, among which one crossed the K-Pg boundary. This study proposes the first analysis of tethysuchian diversity from the Late Jurassic to the Early Paleogene. Two diversity peaks are observed during the Oxfordian and Cenomanian, two stages of high paleotemperatures evaluated with the δ18O. The tethysuchian diversity strongly decreases after the Cenomanian, a decline that may be correlated with the “Ocean Anoxic Event” (OAE 2), which caused the strong marine faunal turnover during the Cenomanian-Turonian time interval. The large Turonian-Coniacian oceanic regression could also be a factor in the tethysuchian decline. After that, tethysuchian diversity remains low until the Maastrichtian-lower Paleocene marine tethysuchian dyrosaurid diversification, correlated with the Late Cretaceous-Paleocene transgression. At least one pholidosaurid lineage crossed the K-Pg boundary, confirming the weak impact of this crisis on the crocodylomorphs. Pholidosaurids seem to go extinct at the beginning of the Paleocene, possibly due to the strong radiation of dyrosaurids in marine environments and crocodylians in fresh-water during this time period.  相似文献   

12.
The Lechówka section comprises the most complete Cretaceous–Paleogene (K-Pg) boundary succession in Poland and is among 29 sites worldwide with the youngest ammonite record. Here, cephalopods (ammonites and nautilids), organic-walled dinoflagellates (dinocysts) and foraminifera from the uppermost Maastrichtian interval are studied. In terms of ammonite biostratigraphy, the upper Maastrichtian Hoploscaphites constrictus crassus Zone is documented up to a level 120 cm below the K-Pg boundary. There is no direct, ammonite-based evidence of the highest Maastrichtian H. constrictus johnjagti Zone. However, the predominance of the dinocyst marker taxon Palynodinium grallator suggests the presence of the equivalent of the uppermost Maastrichtian Thalassiphora pelagica Subzone, which is correlatable with the H. c. johnjagti ammonite Zone. The planktonic foraminiferal assemblage is coeval with that from the H. c. johnjagti Zone as well. These data indicate that the top of the Maastrichtian at Lechówka is complete within the limits of biostratigraphic resolution, albeit slightly condensed. The dinocyst and foraminiferal assemblages are dominated by taxa that are characteristic of high-energy, marginal marine environments. A reduction in test size among the calcareous epifaunal benthic foraminifera is observed at a level 50 cm below the K-Pg boundary, which is possibly related to environmental stress associated with Deccan volcanism.  相似文献   

13.
The Late Cretaceous (Maastrichtian) to early Paleocene (Thanetian) shallow water (<100 m) agglutinated foraminifera from a section at Dakhla Oasis (Western Desert, Egypt) were analyzed for their assemblage, species and genera distribution, diversity, depositional environment, community structure and palaeobathymetry with respect to regional tectonics, climate and global eustasy. Data suggest an equitable benthic environment with low species dominance deposited in a brackish littoral and/or marsh setting. Sea level curves using characteristic benthic foraminiferal species, genera and assemblages corroborate quantitatively generated estimate and statistical analysis. Data suggests that in the absence of or of an impoverished benthic foraminiferal fauna, a high resolution agglutinated foraminiferal dataset can be as good a predictor of the benthic community structure and environment, as its calcareous counterpart, at least for shallow settings (<100 m). Present data also provides a good window in better understanding the distribution and interrelationship between the three dominant genera, Haplophragmoides, Trochammina and Ammobaculites. Faunal changes at boundaries (Cretaceous/Paleogene, Danian/Selandian and Selandian/Thanetian) are also evaluated.  相似文献   

14.
Geochemical and isotopic analyses of the Cretaceous–Paleogene (K/Pg) boundary deposits were conducted at the Caravaca section (External Subbetic, southeast of Spain) in order to evaluate the recovery of the macrobenthic tracemaker community and the bioturbational disturbance. Samples from the infilling material of several lower Danian dark-colored trace fossils (Chondrites, Planolites, Thalassinoides and Zoophycos) located in the uppermost 8-cm of the light upper Maastrichtian strata, as well as samples from the host sedimentary rock of these trace fossils, were analyzed and compared with data from the lower Danian deposits. The values of element ratios indicative of extraterrestrial contamination (Cr/Al, Co/Al and Ni/Al) are higher in the infilling trace fossil material than in the upper Maastrichtian and lower Danian deposits, which suggests a contribution of the ejecta layer. Regarding the isotope composition, the δ13C values are lower in the infilling material than in the Maastrichtian host sedimentary rocks surrounding the traces, while the δ18O are higher in the infilling material. The geochemical and isotopic compositions of the infilling material evidence the unconsolidated character of the sediment, including the red boundary layer. Softground conditions confirm a relatively rapid recovery by the macrobenthic tracemaker community, starting a few millimeters above the K/Pg boundary layer. The mixture of the infilling material of the trace fossils moreover reveals a significant macrobenthic tracemaker activity affecting K–Pg boundary transition sediments that may have significantly altered original signatures.  相似文献   

15.
A new biostratigraphic correlation for Late Cretaceous and Palaeocene strata of the Côte d’Ivoire–Ghana continental margin has been developed from the identification of significant dinoflagellate cyst events in ODP Hole 959D. The Late Cretaceous stage boundaries are mostly consistent with previous studies. However, the Maastrichtian/Danian boundary is placed much lower than previously recognized on the basis of the first occurrences of Carpatella cornuta and Damassadinium californicum. The base of the Selandian is recognized from the last occurrence of Cerodinium diebelii and the first occurrence of Adnatosphaeridium multispinosum. The base of the Thanetian is recognized from the first occurrence of Areoligera gippingensis. The rarity of the age-marker taxa is the main reason for different age determinations among studies of the same section.  相似文献   

16.
The biostratigraphy and the response of calcareous nannofossils to the End Cretaceous warming are investigated in the lower boundary of Kalat formation through the record of species richness, diversity, distribution patterns, and statistical treatments. The Kalat formation comprised of coarse-grained detritus limestone with subordinate sandstone intercalations. In the studied sections, the number of ten samples were taken and prepared with smear slide. In Dobaradar, section 22 species; in Kalat, section 25 species; and in Chahchaheh, section 32 species have been determined. Based on nannoplanktons and as a result of biostratigraphic studies, the nannofossil standard zones (CC25–CC26) were identified in all of sections. According to these zones in all of sections, the age of the studied thickness is Late Maastrichtian–Late Late Maastrichtian. In these sections, the presence of Micula murus at the end of Neyzar formation and the presence of this species at the lower part of Kalat formation indicate that the investigated boundary is Late Maastrichtian in age. The paleoecological results point to warm climate. The presence of warm water indicators (M. murus and Micula prinsii) and the absence of cool water indicators (Ahmuellerella octoradiata, Kamptnerius magnificus, and Nephrolithus frequens) suggest warm surface water conditions in these areas. In the lower boundary of Kalat formation, base on Lithraphidites spp. and Watznaueria barnesae, lowered fertility condition with low productivity at the end of the Maastrichtian were suggested, and the studied area was deposited in shallow marine environment in relatively low latitude.  相似文献   

17.
New carbon (δ13C) isotope records calibrated by planktonic bioevents provide general support for a late Campanian age assignment of the Shiranish Formation (Fm.) and its boundaries in the Dokan section (NE Iraq). The Shiranish Fm. is characterised at the base by a mid-Campanian unconformity as can be interpreted by absences of nannofossil zones CC20-21. The Shiranish Fm. then spans nannofossil biozones CC22-CC23a (UC15d-eTP to UC16aTP). Results obtained on carbon isotopes suggest that diagenesis affected and compromised a few carbonate samples in the uppermost 50 m of the section. However, once these samples are discarded, pristine trends suggest that the top of the section records a negative carbon isotope excursion that is interpreted as CMBa-c events that straddle the Campanian–Maastrichtian boundary. This interpretation is supported by the lowermost occurrence of planktic foraminifers Rugoglobigerina scotti and Contusotruncana contusa some 30 m above the base of the negative excursion and 10 m below a positive excursion identified as the Maastrichtian M1+ event. Discrepancies in the stratigraphic range of several planktic foraminifer bioevents are highlighted and advocate for the need of many more integrated records of planktic foraminifer and nannofossil biostratigraphy alongside carbon isotope stratigraphy in the eastern Tethys in order to improve regional and global schemes.  相似文献   

18.
A rich dinoflagellate cyst assemblage has been recovered from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the South Iranian Basin. Key dinoflagellates recorded in the section studied provide a means of correlation with zonation schemes for Australasia and north-west Europe. These include Eucladinium kaikourense, Nelsoniella aceras, Odontochitina spp., Cannosphaeropsis utinensis, Palaeocystodinium denticulatum and Dinogymnium spp. The assemblage points to a late Santonian–late Maastrichtian age for the Gurpi Formation. Dinoflagellate and planktonic foraminiferal evidence indicates the presence of a hiatus spanning the uppermost Maastrichtian to at least the lowermost Danian at the base of a glaucony-rich layer separating the Gurpi Formation from the overlying Pabdeh Formation. Palynofacies and lithofacies profiles suggest that the sediments were deposited in an open, relatively deep marine outer ramp environment belonging to ramp facies 8 and 9.  相似文献   

19.
The Maastrichtian regressive sequence of the Hekimhan-Malatya area in Eastern Turkey consists of dolomitic limestones, limestones and calcareous mudstones which are dominated by rudists and Loftusia (foraminifera) assemblages. Several Loftusia species indicating middle to late Maastrichtian age such as Loftusia anatolica Meriç, L. baykali Meriç, L. coxi Henson, L. harrisoni Cox, L. minor Cox and L. morgani Douvillé have been recorded. Other benthic foraminifers present include Orbitoides medius d’ Archiac, Omphalocyclus macroporus (Lamarck), Laffitteina conica Drooger, Laffitteina mengaudi (Astre) and Laffitteina oeztuerki Inan. The rudists are abundant in the dolomitic limestones in the study area. The genus Miseia Patrulius is dominant and represented by Miseia bilacunosa Özer and Miseia hekimhanensis Karacabey-Öztemür. The Loftusia species and the Rudists assemblage indicates middle to late Maastrichtian age for the formation. The paleobiogeographic distribution of the assemblage has been discussed taking this find into account.  相似文献   

20.
Integration of calcareous nannofossil data, δ13C and δ18O values, and carbonate contents of the lower Paleocene–upper Paleocene sequence that crops out at the Misheiti section, East Central Sinai, Egypt, were used to denote the Danian/Selandian (D/S) and Selandian/Thanetian (S/T) stage boundaries. The study interval belongs to the Dakhla and Tarawan formations. Four calcareous nannofossil zones (NP4, NP5, NP6, and NP7/8) were recognized. The base of the Selandian Stage is tentatively placed at the lowest occurrences (LOs) of taxa ascribable to the second radiation of fasciculiths (i.e., Lithoptychius janii). This level is marked by a sudden drop of δ13C and δ18O values and carbonate content. No distinctive lithological changes were observed across the D/S boundary at the study section. A hiatus at the NP5/NP6 zonal boundary is indicated by the condensation of zones NP5 and NP6.The base of the Thanetian is placed at the base of Zone NP7/8 at the lithological change observed in correspondence to the boundary between the Dakhla and Tarawan formations. The δ13C and δ18O values abruptly decrease slightly above the base of Zone NP7/8. No consistent variations in the carbonate contents were recorded within Zone NP6 or across the NP6/NP7/8 zonal boundary.  相似文献   

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