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121.
An extensive study of the ammonoid fauna occurring in the lagoonal facies of a Middle Triassic isolated carbonate platform (Latemar platform, Dolomites, Italy) has been undertaken, and ammonoids from selected coeval successions (Punta Zonia, Marmolada, Rio Sacuz) have been illustrated. Ammonoids from Latemar have been collected in 20 distinct horizons (storm deposits) within the ca. 500 m thick lagoonal succession of the platform, thus providing a biostratigraphy of a series which is unusually expanded for this time interval, close to the Anisian-Ladinian boundary. Contrary to general opinion, some ammonoids of the Latemar and other coeval carbonate platforms of the Dolomites (Marmolada, Cernera), in particular Aplococeras avisianum, Lecanites misanii, Celtites spp., and Paranevadites sp., are also present in nearby basinal series. The same taxa have been found in North American localities deposited at the opposite margin of Panthalassa. The homotaxis of these ammonoids in North America and Latemar allow to establish a global scale correlation between the Southern Alps and North America with the highest resolution to date possible. In the context of this study, Aplococeras transiens n. sp. and Esinoceras nerinae n. sp are established. 相似文献
122.
Ladislav Slavík 《Geobios》2004,37(4):454
Six Pragian-Emsian boundary sections in the Barrandian area, western of Prague, provided evidence of well detectable entries of Latericriodus fauna probably at the earliest Emsian beds (particularly Latericriodus bilatericrescens gracilis Bultynck). The chance to find icriodontid conodonts increases with latest part of Praha Fm., which is apparently of Emsian age, whereas polygnathids are sparsely preserved to absent. The high icriodontid/polygnathid ratio links together all these Barrandian sections, although their open-sea depositional environments range widely from deep troughs with rapid calciturbidite accumulation (Pod Barrandovem section) to relatively starving slope environments on elevations (Na Po?árech sections). The reports on polygnathid occurrences around the Pragian-Emsian boundary beds of the Barrandian area are much biased by poor reproducibility of the results (the conodonts cannot be found again) as well as by different levels where they were randomly found and/or by major taxonomic problems with the “kitabicus” and “dehiscens” definitions and their stratigraphic use. Apart from the GSSP in the Zinzilban Gorge (Uzbekistan) and its “kitabicus” boundary, the newly introduced “gracilis” biostratigraphic-marker concept preserves the major volume of the Pragian and respects also approximately the base of the traditional Emsian. These “gracilis” entries are clustered around the dark-colored “graptolite-bearing interval” beds, which largely form a prominent lithological marker within the latest, light gray-colored Dvorce-Prokop Limestone of the Barrandian area. This “gracilis” biostratigraphic marker has a promising correlation potential relative to Spanish and Moroccan sections. 相似文献
123.
B.P. Lutz S.E. Ishman D.F. McNeill J.S. Klaus A.F. Budd 《Marine Micropaleontology》2008,69(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
124.
The biostratigraphy (larger foraminifers, dasycladaleans), microfacies, sedimentology, and geochemistry (δ
13C, strontium-isotope stratigraphy) of a continuous, 148-m-thick section of shallow-water platform carbonates that contain
the Cretaceous/Paleogene (K/P) boundary were analyzed. The boundary is constrained within a 7-m-thick interval, between the
last occurrence of Maastrichtian larger benthic foraminifers and the first occurrence of Danian benthic foraminifers. Although
this interval is intensively dolomitized, there is no sedimentological evidence of a major hiatus at the K/P boundary. The
correlation of bulk rock δ
13C values with stable isotope data from DSDP Site 384 (NW Atlantic Ocean) supports this interpretation and indicates a Selandian
age for the top of the section. The Qalhat section is a unique example of a carbonate platform that has recorded persisting
open marine environmental conditions across the K/P boundary (Maastrichtian–Selandian), as indicated by the abundance of rudists,
larger benthic foraminifers (Maastrichtian), calcareous algae and scleractinian corals. 相似文献
125.
126.
The Cenomanian–Lower Turonian succession exposed in west central Sinai is carefully studied for their ostracode content. The Raha and Abu Qada Formations were studied in 4 sections. Their ostracode content includes the recognition of 70 species belonging to 34 genera. One species is considered as new (Spinoleberis grosdidieri n. sp.). The vertical distribution of the ostracodes in the sections enables the detection of four local biostratigraphic zones with a Barren Interzone in between. In terms of paleobathymetry, each studied sequence reveals deposition on a shallow reefal carbonate platform of less than 100 m depth. The flourishing of cytherellids in repeated intervals refers to kenoxic events within the Cenomanian section. These events are enhanced just below the Cenomanian–Turonian boundary referring to the Oceanic Anoxic Event 2. The wide paleobiogeographic distribution of the recorded Cenomanian ostracodes reveals that there was a direct connection throughout the Southern Tethyan Realm countries. Also, there was a migration path between the Southern Tethyan bioprovince and the West African bioprovince during the Cenomanian via the Trans-Saharan Seaway and along the Atlantic coast of West Africa. 相似文献
127.
The ostracod fauna collected from the Cherahil formation that crops out at the Jebel Serj section (central Tunisia) contains 24 species belonging to 12 genera. These ostracods are associated with 9 genera of benthic Foraminifera (including 4 Nummulites species) and 7 genera of planktonic Foraminifera. The biostratigraphic study of ostracod assemblages results to the recognition of 6 biozones which are correlated with Lutetian-Priabonian. The Shannon Weaver, Margalef and equitability indices point to internal platform netritic conditions, with minor fluctuations in depth and oxygenation. The palaeobiogeographic distribution of ostracod species found in the study area of Central of Tunisia establishes a good connexion with the basins developed in Northern Africa (Tunisia, Algeria, Libya and Mauritania) and the Middle East (Egypt and Jordan). 相似文献
128.
《Revue de Micropaléontologie》2015,58(3):217-237
The Tournaisian beds of the Kahanag section in central Alborz (northern Iran) are described. This Tournaisian is probably complete and continuous from MFZ1 to MFZ8 biozones; nevertheless, (1) the base is only lithostratigraphically characterized, (2) the biozones MFZ1 to MFZ5 cannot be differentiated, and (3) in topmost beds, Eoparastaffella simplex indicative of the basal Viséan have not yet found. This Tournaisian is subdivided into a local lower Tourmaisian (MFZ1-MFZ5) showing a poor assemblage of monolocular and bilocular foraminifers, and a local upper Tournaisian where the biozones MFZ 6 and 7 are precisely defined. In Kahanag, MFZ 6 is characterized by the FO of Eotextularia diversa; MFZ 7 is the range-zone of Darjella monilis; and the base of MFZ8 is marked by the appearance of Eoparastaffellina. The biozone MFZ 8 is particularly developed in Kahanag, and represents almost one third of the field-section; therefore, a local subdivision is proposed, especially in order to characterize an upper MFZ8 subbiozone. Additionally, some algae of the section are accurately described; especially a trio which might be characteristic of the latest Tournaisian in Iran, (1) the unilayered “Koninckopora” mentioned for the first time in Iran; (2) a new genus of dasycladaleans Kahanagella n. gen.; and (3) a new genus of palaeoberesellaceans, Oblikamaena n. gen. More classical Algospongia (incertae sedis algae) are briefly mentioned Issinella, Crassikamaena, Kamaena, Palaeoberesella, Exvotarisella, Pseudostacheoides, Sinustacheoides and Stacheoides. Regionally, the new genus Kahanagella might be an important palaeobiogeographic marker because it was also discovered in the Tabas Block, while it seems absent in the adjacent, well-known areas (Taurus, southern Urals, Kazakhstan). Perhaps, Kahanagella might permit to reconstruct the initial geography of the latest Tournaisian Iranian platforms. Oblikamaena elbursica n. gen. n. sp. is an endemic taxon for the moment but might become also palaeobiogeographically interesting. Finally, the whole foraminiferal and algal Tournaisian assemblage permits to propose a reconstruction of the initial palaeoposition of the Iranian terranes prior to the progressive assemby of the Cimmerian terranes. 相似文献
129.
Carlo Corradini Maria G. Corriga Peep Männik Hans Peter Schönlaub 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2015,48(1):56-71
The Cellon section, located in the Carnic Alps, is a reference section for the Silurian of the world. The conodont association of the section is revised according to the most recent taxonomy and the biostratigraphy updated in the basis of the recently published zonation schemes. Seventy taxa (species and sub‐species) belonging to 23 genera have been identified, allowing the discrimination of 15 biozones from the upper Llandovery to the end of the P?ídolí . However, some of the uppermost Llandovery and Wenlock biozones, corresponding to black shale intervals, have not been documented. 相似文献
130.
《Geobios》2020
Bouleiceras is a very rare genus among the rich assemblages of ammonoids from the lower Toarcian of the Iberian Range. So far, only two dozen specimens have been recorded in numerous field campaigns carried out since 1965 by different authors. The interest of this taxon lies in its peculiar paleogeographical distribution in comparison with most other ammonoids of the same age. A review of these specimens is carried out, including those obtained in previous works and others recently collected in selected localities. Based mainly on the differences in the shape of the ventral section and the suture line, seven species have been identified; two of which are new: Bouleiceras ibericum nov. sp. and Bouleiceras? betetensis nov. sp. All the reviewed specimens are recorded in the Semicelatum Subzone of the Tenuicostatum Zone and the Elegantulum Subzone of the Serpentinum Zone from the Central Sector and the Levantine Sector of the Iberian Range. The global distribution of the genus is summarized from the known data, and its possible dispersal routes are analyzed, as well as the factors that could have conditioned them. 相似文献