Radiolaria, planktonic foraminifera, and stratigraphy of Turonian-lower Coniacian in the Biyuk-Karasu section, Crimea
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Radiolaria
Section (typography)
The rarity of radiolaria in rocks of Upper Cretaceous age is a remarkable fact, and one for which it is not easy to account, seeing that they are not uncommon in Lower Cretaceous rocks on the Continent, and that they have been found in beds of Jurassic age in France, Hanover, and Bavaria. One would moreover have expected the physical conditions of the Upper Cretaceous period to have been more favourable to their existence than those of Lower Cretaceous or Jurassic times. It will be seen, from the descriptions which follow, that one cause of their rarity is undoubtedly the facility with which the siliceous skeletons of Polycystina disappear, when they are embedded in rocks which contain a large proportion of carbonate of lime. Our knowledge of Upper Cretaceous radiolaria comes chiefly from Germany. In 1876 Prof. Zittel described six species, occurring in a Greensand of Senonian age in Westphalia and Brunswick. In 1888 Dr. Rüst described some well-preserved forms which he had detected in phosphatic nodules from the Gault of Saxony, Hanover, and Southern France, and in material filling the body-chambers of ammonites from the same formation. He also described Dictyomitra anglica from flints in the Upper Chalk of England ( op. cit. p. 211 & pl. xxviii. fig. 16) and Dictyospyris chlamydea , same occurrence ( op. cit. p. 204). Besides those in the English flints mentioned by Riist there are only two records of the occurrence of radiolaria in English Cretaceous deposits.Prof. W. J. Sollas, in 1873, describing the coprolites
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Larger foraminifera were collected from various Paleocene and Eocene localities in western Cuba. Included was a mea- sured section at San Francisco de Paula in Ciudad de la Habana Province in the Apolo and Capdevila Formations. This section spans the Paleocene/Eocene boundary and has been the focus of intensive biostratigraphic work. In this study, the stratigraphic occurrences of the larger foraminifera were correlated to biozonations based on planktonic foraminifera, calcareous nannofossils, radiolaria, and smaller benthic foraminifera already identified at San Francisco de Paula. Most of the above localities consist of synorogenic sedimentary rocks and the larger foraminifera collected from these sites have in fact been transported to deep water. In order to obtain some in situ larger foraminfera, additional upper Paleocene and lower Eocene samples were obtained from 10 wells in episutural basins from throughout Cuba. In all, eleven species of larger foraminifera were identified from the upper Paleocene and lower Eocene of Cuba. These are: Ranikothalia catenula (Cushman and Jarvis) (=Operculina catenula 1932), Discocyclina barkeri Vaughan and Cole, Discocyclina anconensis Barker, Discocyclina weaveri Vaughan, Eoconuloides lopeztrigoi (Palmer) (=Amphistegina lopeztrigoi 1934), Eoconu- loides wellsi Cole and Bermudez, Eofabiania cushmani (Vaughan) (=Discocyclina cushmani 1929), Athecocyclina stephensoni (Vaughan) (=Discocyclina stephensoni 1929), Pseudophargmina cedarkeysensis, Cole, Hexagonocyclina cristensis (Vaughan) (=Orbitoclypeus? cristensis 1924), and Cushmania americana (Cushman) (=Conulites americana 1919). The larger foraminifera from Paleocene age samples contain an assemblage recognized throughout the Caribbean and Gulf Coastal Plain as the Ranikothalia catenula fauna. Eocene samples contain an assemblage of larger foraminifera refered to here as the Eoconuloides wellsi fauna. Based onI data collected at the San Francisco de Paula section, the change from the Ranikothalia catenula fauna to the Eoconuloides wellsi fauna appears to post-date the benthic faunal turnover associated with the bathyal realm.
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A systematic study was carried out on the relatively rich and abundant Paleocene to late Oligocene radiolarian fauna from DSDP Site 329 (Leg 36), located on the Falkland Plateau. Among the 78 taxa identified in the studied interval, a new species (Siphocampe ewingensis n. sp.) and a new combination (Eucyrtidium amygdala (Shilov 1995) n. comb. are proprosed. The high-latitude radiolarian interval zones Eucyrtidium antiquum, Lychnocanoma conica and Clinorhabdus robusta, Oligocene in age, were identified in the upper part of the interval. The lowermost studied sample, within core 33, was assigned to an interval of high-latitude radiolarian zones (RP2-RP5; Paleocene in age), mainly due to the co-occurrence of Amphisphaera kina and Protoxiphotractus wilsoni. These biostratigraphic results improve resolution in the early and late Oligocene, whichwas previously undifferentiated asOligocene, based on calcareous nannofossil biostratigraphy.
Radiolaria
Paleogene
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