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1.
Radiolarians from the Upper Triassic of the allochthonous Mamonia Assemblage of southern Cyprus are considered. The Phasoula Formation, composed of basic volcanics, with lenses and interbeds of micritic limestones and cherts, contains (1) a Lower Norian assemblage with Capnodoce crystallina-Trialatus robustus, which also includes Capnodoce anapetes De Wever, Capnuchosphaera deweveri Kozur et Mostler, C. theloides De Wever, Deflandrecyrtium curvatum Kozur et Mostler, Icrioma cruciformis Tekin, Kahlerosphaera norica Kozur et Mock, Kinyrosphaera helicata Bragin, Mostlericyrtium sitepesiformis Tekin, Palaeosaturnalis latiannulatus Kozur et Mostler, Spongostylus tortilis Kozur et Mostler, Xiphotheca rugosa Bragin, and Zhamojdasphaera proceruspinosa Lahm; (2) a Middle Norian assemblage with Capnodoce sarisa accompanied by Loffa mulleri Pessagno, Nabolella trispinosa Bragin, and Praexehasaturnalis tenuispinosus (Donofrio et Mostler); and (3) an Upper Norian assemblage with Livarella densiporata-Lysemelas olbia accompanied by Pentactinocarpus sevaticus Kozur et Mostler, Praemesosaturnalis multidentatus (Kozur et Mostler), and others. This assemblage also occurs in clastic turbidites of the Vlambouros Formation. In the sections of southern Cyprus, radiolarian zones are recognized that correspond to the zones previously established in the Far East of Russia, which include Capnodoce crystallina (Lower and Middle Norian) and Lysemelas olbia (lower part of the Upper Norian). Radiolarians belonging to three orders, 24 families, 59 genera, and 101 species are described; of them 2 genera, 9 species, and 1 subspecies were previously described by the author; 14 new species and 1 new subspecies are established. The diagnoses of many genera and species are emended, the stratigraphic and geographical ranges of the majority of taxa are substantially expanded.  相似文献   

2.
A diverse and well-preserved latest Permian radiolarian fauna was obtained from bedded siliceous rocks and siliceous mudstones of the Dongpan Section, southwest Guangxi, China. All encountered specimens of the order Spumellaria and a few specimens of the order Entactinaria were selected for the taxonomic study of this paper. Thirty-three species, 15 of which are new species, were identified. They belong to 15 genera, three of which (Paracopicyntra, Copiconulus, and Yujingella) are new. The most interesting result of our study is that eight typical Middle Triassic spumellarian genera (Paroertlispongus Kozur and Mostler, Tetrapaurinella Kozur and Mostler, Paurinella Kozur and Mostler, Lithelius Haeckel, Archaeospongoprunum Pessagno, Tamonella Dumitrica, Kozur and Mostler, Bistarkum Yeh, and Tetraspongodiscus Kozur and Mostler) were discovered in the upper Changhsingian strata studied herein. Therefore, the most important and characteristic spumellarian families of the Middle Triassic were already present in the Late Permian of South China.  相似文献   

3.
Triassic radiolarians from Kotel’nyi Island (New Siberian Islands, Arctic Region) are studied. Radiolarians occur in the Middle and Upper Triassic beds, which are well dated by ammonoids, nautiloids, and bivalves. In the Middle Triassic beds, which are composed of dark gray and black clays and claystones with interbeds of combustible schist, siltstone, clayey limestone, and many phosphatic concretions, the following two assemblages are recognized: (1) a Late Anisian assemblage, including Glomeropyle clavatum Bragin, sp. nov., G. boreale Bragin, G. manihepuaensis Aita, G. insulanum Bragin, sp. nov., Triassospongosphaera multispinosa (Kozur et Mostler), Tetraspongodiscus hibernus Bragin, sp. nov., T. borealis Bragin, sp. nov., Eptingium abditum Bragin, sp. nov., E. manfredi Dumitrica, Spongostephanidium japonicum (Nakaseko et Nishimura), and Ladinocampe vicentinensis Kozur et Mostler; (2) Late Ladinian assemblage, with Muelleritortis firma (Gorican), M. kotelnyensis Bragin, sp. nov., Tiborella nivea Bragin, sp. nov., Pseudostylosphaera goestlingensis (Kozur et Mostler), P. omolonica Bragin, Triassospongosphaera multispinosa (Kozur et Mostler), Sarla cincinnata Bragin, sp. nov., S. obscura Bragin, sp. nov., S. prava Bragin, sp. nov., and Eonapora stiriaca Bragin, sp. nov. The Upper Triassic beds, composed of gray and black clays and claystones with lenses of clayey limestones, with sideritic and phosphatic-calciferous concretions have yielded (1) an Early Carnian assemblage, with Pentactinocarpus colum Bragin, sp. nov., Glomeropyle cuneum Bragin, sp. nov., G. algidum Bragin, sp. nov., G. aculeatum Bragin, sp. nov., Kahlerosphaera isopleura Bragin, sp. nov., Stauracanthocircus folium Bragin, sp. nov., Tetraspongodiscus uncatus Bragin, sp. nov., Poulpus costatus (Kozur et Mostler), Eonapora robusta Kozur et Mostler, Planispinocyrtis kotelnyensis Bragin, sp. nov., Annulotriassocampe baldii (Kozur), and Pseudoeucyrtis annosus Bragin, sp. nov.; (2) a Middle-Late Carnian assemblage with Pseudostylosphaera glabella Bragin, sp. nov., P. gracilis Kozur et Mock, P. voluta Bragin, sp. nov., P. gelida Bragin, sp. nov., Kahlerosphaera unca Bragin, sp. nov., K. aspinosa Kozur et Mock, K. fuscinula Bragin, sp. nov., K. acris Bragin, sp. nov., Capnuchosphaera kuzmichevi Bragin, sp. nov., C. triassica De Wever, C. angusta Bragin, sp. nov., Sarla intorta Bragin, sp. nov., S. compressa Bragin, sp. nov., S. aequipeda Bragin, sp. nov., Betraccium irregulare Bragin, B. kotelnyensis Bragin, sp. nov., Spongotortilispinus carnicus Kozur et Mostler, S. subtilis Bragin, sp. nov., Dumitricasphaera simplex Tekin, D. aberrata Bragin, sp. nov., D. arbustiva Bragin, sp. nov., Zhamojdasphaera epipeda Bragin, sp. nov., Z. proceruspinosa Kozur et Mostler, Vinassaspongus subsphaericus Kozur et Mostler, Palaeosaturnalis triassicus Kozur et Mostler, Paronaella concreta Bragin, sp. nov., P. aquilonia Bragin, sp. nov., Tetraspongodiscus cincinnalis Bragin, sp. nov., Annulotriassocampe baldii (Kozur), Canoptum zetangense Wang et Yang, Whalenella speciosa (Blome), Syringocapsa turgida Blome, Droltus gelidus Bragin, sp. nov., and D. niveus Bragin, sp. nov.; (3) an Early Norian assemblage with Pseudostylosphaera glabella Bragin, sp. nov., P. gelida Bragin, sp. nov., P. voluta Bragin, sp. nov., Kahlerosphaera retunsa Bragin, sp. nov., Capnuchosphaera deweveri Kozur et Mostler, Sarla globosa Bragin, sp. nov., Palaeosaturnalis mocki Kozur et Mostler, Paronaella aquilonia Bragin, sp. nov., Syringocapsa turgida Blome, and Droltus gelidus Bragin, sp. nov.; (4) a Middle Norian assemblage with Sarla globosa Bragin, sp. nov., Sarla sp., Syringocapsa turgida Blome, Canoptum sp., and Laxtorum? sp. The fact that these assemblages include taxa that are recorded more southerly, including paleotropical localities, and support dating based on mollusks, enables the use of these data for Boreal-Tethyan correlation. The greatest similarity to Tethyan associations is observed in the Late Carnian and Early Norian, that is, the periods of the greatest penetration of thermophilic mollusks into this basin. A total of 69 radiolarian species of 3 orders, 18 families, and 29 genera are described; 44 species are newly described; the stratigraphic and geographical ranges of the majority of taxa are improved considerably.  相似文献   

4.
A poorly preserved, but diversified radiolarian fauna was recovered from thin-bedded cherts occurring in the southeast of Daofu, Sichuan Province, southwestern China. Twenty-two radiolarian species belonging to 10 genera are identified and three new species (Paroertlispongus daofuensis n. sp., Falcispongus heinzi n. sp., Falcispongus pauliani n. sp.) are described. Falcispongus heinzi represents a transitional species between genera Oertlispongus inaequispinosus Dumitrica, Kozur and Mostler and Falcispongus Dumitrica. The fauna is divided into two assemblages, namely Muelleritortis cochleata and Oertlispongus inaequispinosus assemblages, which can be well correlated with the Ladinian radiolarian zones from Europe. The fauna indicates that basaltic rocks occurring in the Xianshuihe Belt were formed mainly during the Middle Triassic. Our results thus extend the previously known geological age of the Xianshuihe Belt to the Middle and Late Triassic interval.  相似文献   

5.
本文描述的海参骨片化石采自西藏申扎县木纠错西的多布日一带,主要有Theelia planorbicula Mostler,Theelia uariabilis alouakensis Kzour et Mock等晚三叠世诺利期标准分子。充分显示了海参骨片化石的重要的生物地层意义。该动物群的发现首次确定了西藏自治区北部冈底斯一腾冲地层区永珠蛇绿岩带以南晚三叠世海相地层的存在,并为中特提斯海的演化历史,古地理轮廓的确定,以及青藏高原的形成演变历史提供了新的资料。  相似文献   

6.
Two radiolarian assemblages were recovered from upper Norian strata of the Kotel’nyi Island (Russia); the first assemblage, from the Monotis zabaikalica Subzone (lower part of Upper Norian), is represented by Betraccium inornatum Blome, Dumitricaella (?) parva Sugiyama, Ferresium titulense Blome and 24 other species; the second assemblage, from the Monotis subcircularis Subzone (upper part of Upper Norian), is represented by Crucella sp. cf. C. angulosa Carter, Kahlerosphaera acris Bragin, K. sp. cf. K. parvispinosa Kozur & Mostler, Pseudohagiastrum crassum (Carter) and 11 other species. Both assemblages have common taxa with Upper Norian and Rhaetian radiolarian assemblages of British Columbia and they display clear Boreal features: low taxonomic diversity, abundance of taxa known from high-latitude regions, absence or rare presence of taxa known from low-latitude areas. The presence of early representatives of nassellarian genera Droltus and Parahsuum is very distinctive. Six new species are described: Pseudohagiastrum spinosum nov. sp., Cantalum boreale nov. sp., Plafkerium carteri nov. sp., Droltus guttaeformis nov. sp., Laxtorum blomei nov. sp., L. glacialis nov. sp.  相似文献   

7.
The Cenomanian Smail Marl Formation in the Bellezma and Aures mountains of northeastern Algeria is well exposed and rich in macroinvertebrates, including cephalopods. Twenty-five ammonite species and two nautiloid species from the Thénièt El Manchar, Djebel Metrassi and Djebel Bouarif sections are described and seven assemblage zones proposed as provisional working units: Mantelliceras mantelli–Sharpeiceras laticlavium Assemblage Zone (lower Cenomanian), Mantelliceras dixoni Assemblage Zone (uppermost lower Cenomanian), Cunningtoniceras inerme Assemblage Zone (lower middle Cenomanian), Acanthoceras rhotomagense and Acanthoceras cf. rhotomagense Assemblage Zone (middle middle Cenomanian), Acanthoceras amphibolum Assemblage Zone (upper middle Cenomanian), Acanthoceras jukesbrownei Assemblage Zone (uppermost middle Cenomanian), and Neolobites vibrayeanus Assemblage Zone (lower upper Cenomanian). The lower Cenomanian Mantelliceras mantelli–Sharpeiceras laticlavium Zone is subdivided into the Submantelliceras aumalense, Sharpeiceras schlueteri and Mantelliceras saxbii subzones. The base of the middle Cenomanian is marked by the disappearance of species of Mantelliceras and the appearance of the scleractinian coral Aspidiscus cristatus (Lamarck, 1801), associated with Cunningtoniceras inerme (Pervinquière, 1907). The middle Cenomanian contains abundant A. cristatus and species of Acanthoceras, i.e., A. cf. rhotomagense (Defrance in Brongniart, 1822), A. jukesbrownei (Spath, 1926) and A. amphibolum Morrow, 1935. An ammonite zonal scheme is then applied to the Cenomanian exposed in the Bellezma-Aures mountains located on the southern Tethys margin in Algeria.  相似文献   

8.
Some temporary outcrops at Villers-le-Tourneur/Neuvizy (Ardennes, France), made possible the observation and biostratigraphical dating of Uppermost Callovian to Early Middle Oxfordian poorly known formations. Especially, the “Oolite Ferrugineuse de Villers-le-Tourneur–Neuvizy” is a quite thick marly unit, yielding some silicified fossils well known since the XIXth century. With details, the Formation displays the succession of several faunal associations, characterizing the main subzones of the Cordatum Zone (Late Lower Oxfordian) and the Plicatilis Zone (Early Middle Oxfordian). Amongst many other species, Cardioceras cordatum (Sowerby, 1812) corresponds to a rare taxon or morphotype, yielded by the bottom part of the Formation. Then, the ultimate Lower Oxfordian faunal association is dominated by ammonites related to C. persecans. These Early Oxfordian are widely dominated by the family Cardioceratidae, commonly associated with Aspidoceratidae; such a structure is related to the “subboreal associations”, typically represented in Great Britain. Immediately after the Middle Oxfordian boundary, some “subtethysian” ammonites (mainly Perisphinctidae), occur in a larger number without being dominant, that emphasizing the northern location of the Ardennes margin. Then locally, two faunal associations succeed, which are characterized by C. cordatiforme (with Euaspidoceras perarmatum), and C. densiplicatum, respectively. Both are typical associations of the Vertebrale Subzone (Early Middle Oxfordian).  相似文献   

9.
In Saxony (southeast Germany), the global early Late Cretaceous transgression is reflected by the onlap of shallow-marine siliciclastics of the lower Upper Cenomanian Oberhäslich Formation (Calycoceras naviculare Zone) onto the eastern Erzgebirge, the central part of the emergent Mid-European Island. Based on detailed logging of sections south of Dresden and the study of extensive collection material, the depositional environment and macroinvertebrate assemblages of the Oberhäslich Formation have been reconstructed. This unit, with a mean thickness of 10–15 m, usually shows a fining-upward trend that may become reversed towards the top, was laid down in a single 3rd-order sea-level cycle and is capped by an unconformity at the base of the overlying upper Upper Cenomanian Dölzschen Formation (sequence boundary Cenomanian 5; junction of the Calycoceras naviculare and Metoicoceras geslinianum zones). The macroinvertebrate assemblage of the Oberhäslich Formation, collected mainly from bioturbated, fine- or rarely medium-grained, quartz-rich sandstones, is fairly diverse, comprising nearly 50 taxa, predominantly bivalves (94.3%). Most conspicuous and abundant are relatively large forms such as Rhynchostreon (R.) suborbiculatum (25%) and Inoceramus pictus spp. (21%), eponymous taxa of the Rhynchostreon suborbiculatum/Inoceramus pictus assemblage. Non-bivalve benthic invertebrates are rare and represented by rather poorly preserved irregular and regular echinoids, siliceous sponges, a few gastropods, crustacean remains and a single starfish. Common Thalassinoides and Ophiomorpha burrows indicate that crustaceans were an important part of the infauna. Pervasive bioturbation resulted in a post-depositional homogenization of the sediments while all body fossils are preserved as (composite) internal moulds. The guild structure of the Rhynchostreon suborbiculatum/Inoceramus pictus assemblage shows a predominance of epifaunal and semi-infaunal suspension feeders (95.3%), suggesting eutrophic and unstable “green-water conditions” of an inner-shelf setting. Deposit-feeding biota are rare. The common occurrence of articulated bivalves and storm-induced shell beds indicate episodic rapid burial, most probably by tempestites. A current-influenced, well-oxygenated and nutrient-rich environment slightly below fair-weather base is inferred for the fine-grained sandy, fossiliferous sediments of the Oberhäslich Formation.  相似文献   

10.
In this contribution, two stratigraphic sections are described through the Lower Cretaceous shallow-water platform sediments (Taft formation) from the northern Tethys, which are located in the Yazd Block, Central Iran. Benthic foraminifera are used to propose a biostratigraphy for these successions. They are grouped around several assemblage zones, and several genera and species are reported from the Yazd Block basin for the first time (e.g., Arenobulimina cochleata, Ameltae, Belorusiella sp., Bolivinopsis cf. labeosa, Decussoloculina barbui, Martinotiella jucunda, Myncina bulgarica, Novalesia cornucopia, Sabaudia briacensis, Simplorbitolina manasi). Their presence can provide a better understanding for the paleogeographic reconstruction of the Tethyan seaways. Furthermore, they represent candidates as potential index fossils in the Lower Cretaceous stratigraphy of the Yazd Block. The new biostratigraphic data allow to date the Lower Cretaceous successions between the probable Valanginian and the late Aptian. Based on the absence of early Barremian indicators and also late Aptian markers, two hiatuses are recognized through the Taft formation. This formation also displays a diachrony in ages at its base and top, which suggests the effect of long-term subsidence in the Yazd Block during the Early Cretaceous, following the Cimmerian phase of orogeny.  相似文献   

11.
The Ouarsenis Massif belongs to the Algerian Tell domain, which is considered as the eastern part of the Maghrebian Tethys former margin. The Berriasian-Valanginian Oued Fodda Formation outcropping in the Kef Aïn El Hadjela section, at the foot of the great peak of the Ouarsenis Massif, is composed of marls and laminated and bioturbated limestone alternations. The marl facies reveals diverse microfauna, including crinoids. These latter are represented by: Isocrinida [isocrinids Balanocrinus cf. gillieroni (de Loriol), Percevalicrinus aldingeri Klikushin, Isocrinus? lissajouxi (de Loriol)], Cyrtocrinida [cyrtocrinids (Phyllocrinus sp., Hemibrachiocrinus sp.)], and Roveacrinida gen. indet. sp. indet. [roveacrinids]. All these, with exception of roveacrinids and phyllocrinids, are noted for the first time from Algeria and African continent (southern margin of Tethys in the Maghreb). Knowledge on Cretaceous crinoids formerly described from Algeria is presented. It is also shown that crinoid assemblage and associated invertebrates are typical for relatively shallow, distal depositional setting situated below storm wave base.  相似文献   

12.
A biostratigraphic and systematic study based on belemnites collected along with ammonites was performed on four sections in the Subalpine Basin (SE France): Lac du Castillon and La Baume (Castellane area), Galabrun and Grand Lara (Gap area). The specimens, originating from hemi-pelagic marl-limestone alternations in the lower part of the “Calcaires à Zoophycos” Formation, are dated from Middle Aalenian (Murchisonae Zone) to Lower Bajocian (Humphriesianum Zone). Five belemnite taxa (Megateuthis elliptica, Holcobelus munieri, Htrauthi, Pachybelemnopsis roettingensis, Hibolithes sp.) have been identified, and two more taxa are reported in an open nomenclature (Belemnitida incertae sedis sp. 1 and sp. 2). The biostratigraphic range of the belemnite fauna is established. The new findings contribute to a more detailed understanding of the paleobiogeography of holcobelid belemnites that flourished at the northern margin of the Tethys Ocean and formed a distinct sub-Mediterranean fauna. The association herein described is similar to the fauna of the Calabro-Peloritani Arc (Calabria, Italy), a further hint for the supposed paleogeographic position of the latter during the Middle Jurassic.  相似文献   

13.
The family Palaeolithocycliidae Kozur and Mostler was formerly thought to be ranging from Devonian to Carboniferous. However, a lot of radiolarians assignable to this family were discovered in the late Changhsingian (Latest Permian) of South China. Six species, including Palaeolithocyclia pilata n. sp., Palaeolithocyclia platta n. sp., Paramphibrachium woni n. sp., Klaengspongus spinosus Sashida, Klaengspongus formosus n. sp. and Klaengspongus umbilicatus n. sp., have been identified. In this paper, these species are illustrated and described.  相似文献   

14.
《Comptes Rendus Palevol》2008,7(8):601-606
A partial skull and articulated postcranial elements of Megantereon whitei have been recorded during the 1950s from a karst deposit in the Monte Argentario area (Grosseto). These fossils recently became available for study. The bones are quite well preserved, included in a hard reddish matrix with calcareous clasts. The fossil is part of a faunal assemblage referred to the Late Villafranchian (Early Pleistocene). M. whitei from Monte Argentario is characterised by elongated upper canines, stronger than those of the Upper Valdarno (Tuscany) specimens and similar to the Pirro Nord (Apulia) fossil. The manus is robust, the first phalanges are quite long in comparison to the metacarpals. The Early Pleistocene European M. whitei represents an African element that took part in the faunal dispersal from Africa to Europe that occurred at the Plio-Pleistocene transition.  相似文献   

15.
Summary Stratigraphic and microfacies investigations carried out on the Oligocene sequence exposed at Gabal Bu Husah, northwest of Marada Oasis, south of the Sirte Basin, Libya, showed that the Oligocene sequence conformably overlies the Late Eocene Thamat Formation and unconformably underlies the Early to Middle Miocene Marada Formation (Qarat Jahannam Member). The lithostratigraphic studies of the Oligocene sequence revealed the presence of two rock units, from base to top: 1- Umm Ad Dahiy Formation (Early Oligocene, Rupelian) and 2- Bu Hashish Formation (Late Oligocene, Chattian). The Oligocene sequence yields a rich foraminiferal assemblage with fifty-one benthonic and large formaminiferal species. The foraminiferal analysis allowed to subdivide the sequence into three local foraminiferal assemblage zones, arranged stratigraphically from base to top: 1)Elphidium minutum zone comprising the Umm Ad Dahiy Formation. 2)Miogypsinoides complanatus/Nonion granosus assemblage zone covering the lower two thirds of the Bu Hashish Formation. 3) Zone with abundantNummulites spp., including the upper part of the Bu Hashish Formation. The paleoenvironmental significance of the recorded species is described and discussed. The microfacies studies led to the recognition of eleven microfacies types. These microfacies indicate that the lower part of the Umm Ad Dahiy Formation was deposited in a shallow warm marine environment, but the conditions changed to fluviomarine in the uppermost part. The Bu Hashish Formation was deposited in a shallow-marine, inner-shelf environment (as indicated by the operculinid limestone) but a probable hiatus in its middle part is indicated by the presence of a nummulitic coquina and gypsum beds formed in a lagoonal environment. After returning to a shallow marine environment at the end of Oligocene the marine sedimentation ended.  相似文献   

16.
A rock sample obtained from the Caliza Masiva of the San Emiliano Formation (Bashkirian–early Moscovian) in the Mina Profunda area (NE Villamanín) of the Bodón Nappe (Cantabrian Zone, NW Spain) has yielded numerous brachiopods and fish remains not frequently represented in the fossil record. The brachiopod assemblage comprises 13 taxa and is characterized by phosphatic (Langella, Orbiculoidea) as well as exceptionally preserved silicified calcitic elements (a small chonetid, Composita, Crurithyris, Lambdarina, and two minute terebratulids) as the main faunal components. Of special importance is the record of the microbrachiopod Lambdarina winklerprinsi nov. sp., which reduces the large Viséan–Upper Permian gap in the stratigraphic record of this genus. Conodont elements recovered from the same insoluble residue are indicative of the upper Bashkirian Idiognathoides sulcatus parvus Zone. The accompanying fish remains consist of chondrichthyan teeth and scales, an acanthodian scale and osteichthyan tooth-bearing bones, isolated teeth and isolated scales, representing the first Pennsylvanian ichthyoliths analyzed from the Cantabrian Zone. The limestone beds with selective silicification in the San Emiliano Formation provide an exceptional opportunity to improve our knowledge on the patterns of life diversity over geological time.  相似文献   

17.
《Palaeoworld》2014,23(3-4):314-320
Four recently collected mammal specimens from the Upper Cretaceous (Santonian–?Campanian) Bostobe Formation in the northeastern Aral Sea Region, Kazakhstan are attributed to Asioryctitheria indet. (an edentulous dentary fragment) and the zhelestid Parazhelestes sp. cf. P. mynbulakensis (a maxillary fragment with a double-rooted canine, an M1, and a dentary fragment including m3). These new records double the known mammal fauna from this formation, which previously included the zhelestid Zhalmouzia bazhanovi and Zhelestidae indet. The taxonomic and ecological structure of the mammal assemblage from the Bostobe Formation can, on present evidence, be considered close to the other eutherian dominated Late Cretaceous mammal assemblages of Central Asia. This region is important in particular in the search for Late Cretaceous ancestors of crown-group eutherian mammal clades (Placentalia).  相似文献   

18.
《Marine Micropaleontology》2009,70(3-4):282-296
An assemblage of planktonic foraminifera is described from 125 samples taken from the Cercado, Gurabo, and Mao Formations in the Cibao Valley, northern Dominican Republic. The primary objectives of this study are to establish a biochronologic model for the late Neogene of the Dominican Republic and to examine sea surface conditions within the Cibao Basin during this interval. The Cercado Formation is loosely confined to Zones N17 and N18 (∼ 7.0–5.9 Ma). The Gurabo Formation spans Zones N18 and N19 (∼ 5.9–4.5 Ma). The Mao Formation is placed in Zone N19 (∼ 4.5–3.6 Ma). Changes in the relative abundances of indicator species are used to reconstruct sea surface conditions within the basin. Increasing relative abundances of Globigerinoides sacculifer and Globigerinoides ruber, in conjunction with a decreasing relative abundance of Globigerina bulloides, suggests the onset of increasing sea surface temperature and salinity in conjunction with diminishing primary productivity at ∼ 6.0 Ma. Abrupt increases in the relative abundances of G. sacculifer and G. ruber at ∼ 4.8 Ma suggest a major increase in sea surface temperature and salinity in the early Pliocene. The most likely mechanism for these changes is isolation of the Caribbean Ocean through progressive restriction of Pacific–Caribbean transfer via the Central American Seaway. Periods of high productivity associated with upwelling events are recorded in the upper Cercado Formation (∼ 6.1 Ma) and in the middle Mao Formation (∼ 4.2 Ma) by spikes in G. bulloides and Neogloboquadrina spp. respectively. The timing of major increases in sea surface salinity and temperature as well as decreasing productivity (∼ 4.8 Ma) and periods of upwelling (∼ 6.1and 4.2 Ma) in the Cibao Basin generally corroborate previously suggested Caribbean oceanographic changes related to the uplift of Panama. Changes in sea surface conditions depicted by paleobiogeographic distributions in the Cibao Basin suggest that shoaling along the Isthmus of Panama had implications in a shallow Caribbean basin as early as 6.0 Ma. Major paleobiologic changes between ∼ 4.8 and 4.2 Ma likely represent the period of final closure of the CAS and a nearly complete disconnection between Pacific and Caribbean water masses. This study illustrates the use of planktonic foraminifera in establishing some paleoceanographic conditions (salinity, temperature, productivity, and upwelling) within a shallow water basin, outlining the connection between regional and localized oceanographic changes.  相似文献   

19.
《Palaeoworld》2016,25(1):95-103
Rodents from the Nuhetingboerhe-Huheboerhe area in the Erlian Basin, Inner Mongolia, differ stratigraphically: primitive ctenodactyloids such as Chenomys and Yuanomys are dominant in the upper part of the Nomogen Formation; Tamquammys dominates in the Arshanto Formation; Asiomys, Pappocricetodon, and Yuomys appear in the lower part of the Irdin Manha Formation and Tamquammys is rarer in this formation than in the Arshanto Formation. The assemblage of the upper part of the Nomogen Formation is similar to that of the Lingcha Formation of Hunan, the Wutu Formation of Shandong, the Yuhuangding Formation of Hubei, and the Bumban Member of the Nara-Bulak Formation of Mongolia. The assemblage in the upper part of the Arshanto Formation is correlated with that from the locality Andarak 2 in Kyrgyzstan. The assemblage from the lower part of the Irdin Manha Formation resembles that of the lower part of the Hetaoyuan Formation of Henan.On the basis of the comparison of the rodent assemblages, I consider that the age of upper part of the Nomogen Formation corresponds to the Bumbanian land mammal age. The Bumbanian, Arshantan, and Irdinmanhan land mammal ages are correlated respectively to the early Ypresian, the middle–late Ypresian, and the early Lutetian of the Geological Time Scale. The Bumbanian and Irdinmanhan land mammal ages are also correlated to the early Wasatchian and the early Uintan (or the later Bridgerian) of the North American Land Mammal Ages.  相似文献   

20.
《Palaeoworld》2020,29(2):325-352
The Mechetlino Quarry section is a potential candidate for the Global Section Stratotype and Point (GSSP) for the base of the Global Kungurian Stage on the International Stratigraphic Chart. In 2017, the Mechetlino Quarry section became the part of the First Geopark in Russia, therefore excavation work was carried out to clear it, a road was laid, and infrastructure was developed. Recent evidence to justify the base Kungurian boundary in the Mechetlino section was obtained. Additional conodonts confirmed the data of V.V. Chernykh on the Artinskian–Kungurian transition. Besides Neostreptognathodus pnevi Kozur and Movshovitsch, the second marker (N. lectulus Chernykh) of the base-Kungurian was established. The Artinskian–Kungurian transition of the Mechetlino Quarry section is characterized by the richest associations of small foraminifers, ammonoids, and other groups. The occurrence of mass Clausiuraloceras above the Kungurian boundary, which changed the representative Artinskian association, was identified. Small foraminifers of the Artinskian–Kungurian transition are numerous and include sufficient species to provide a correlation with Western Tethys, Svalbard and Australia. Data on isotopic ratios of δ13C and δ18O, δ13Corg values and the magnetic susceptibility were obtained for the first time.  相似文献   

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