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1.
A. Yu. Gladenkov 《Stratigraphy and Geological Correlation》2006,14(1):73-90
Fossil diatoms from the Milky River Formation of the Sandy Ridge section, Alaska Peninsula are analyzed. Data on stratigraphic distribution of diatoms and silicoflagellates are presented. Based on presence of stratigraphically important forms (Neodenticula kamtschatica, Thalassiosira oestrupii, Cosmiodiscus insignis), the assemblages studied are correlated with the North Pacific Cenozoic diatom zones. An assemblage similar to that of subzone “b” of the Neodenticula kamtschatica Zone (Barron and Gladenkov, 1995) indicates the latest Miocene-initial early Pliocene (5.5-4.8 Ma) age of its host deposits. Additional species of biostratigraphic importance (Thalassiosira temperei, Th. latimarginata, and others) refine ages of different parts of the section. In particular, age of stratigraphically lowest beds bearing Astarte (mollusks valuable for establishing the Bering Strait opening) were dated at 5.5-5.4 Ma. Some paleogeographic inferences are made from analysis of composition of the diatom assemblages. 相似文献
2.
T. V. Oreshkina E. A. Lygina O. A. Vozhzhova A. V. Ivanov 《Stratigraphy and Geological Correlation》2013,21(2):222-236
A representative assemblage of diatoms and silicoflagellates found in a excellent state of preservation is described from terrigenous cherty deposits of the Upper Cretaceous, which are exposed in a quarry near the Kologrivovka village in Saratov Region. The assemblage is correlative with diatoms of the Costopyxis antiqua Zone of the lower Campanian and with silicoflagellates of the Cornua trifurcata Zone, the upper one in the lower Campanian. According to the taxonomic composition, dominated by diatom genera Cortinocornus, Costopyxis, Hemiaulus, Paralia, Pseudopodosira, and Stephanopyxis, the assemblage was typical of a highly productive neritic zone with an active hydrological regime. A perceptible content of silicoflagellates among the diatoms suggests the normal salinity of the sedimentation basin. The comparable sedimentation settings in marginal parts of the Early Campanian epicontinental basin on the south of the East European platform can also be inferred based on the data from the lithological analysis. 相似文献
3.
《Cretaceous Research》1988,9(4):321-336
The type section of the marly Daliyya Formation in Daliyat el Karmil, northern Israel, has been examined for planktonic foraminifera and ostracods. The coexisting assemblages of the upper part of the Helvetoglobotruncana helvetica total range zone (= Marginotruncana sigali interval zone) and of the Cythereis rawashensis kenaanensis assemblage zone indicate that this succession is middle Turonian in age. The depth of deposition varied from neritic (100–200 m) to shallow (≈50 m) with a short littoral episode. The palaeobathymetric oscillations agree rather well with global sea-level changes. Included in this paper are taxonomic remarks on some of the foraminifera and ostracods. 相似文献
4.
西藏拉萨地块设兴组孢粉化石新发现及其地层学意义 总被引：3，自引：0，他引：3
拉萨地体的典中－那玛剖面设兴组上部新发现孢粉组合，其特征为：孢粉化石多为第三纪常见分子，未发现早白垩世和晚白垩世特征分子。因此样品产出的层位不可能属于白垩纪的沉积。孢粉组合以落叶，阔叶植物为主体，主要为桦科的桤木粉（Alnipollenites)，桦粉（Betulaepollenites)，枥粉（Carpiniptes），山毛榉科的栎粉（Quercodites)胡桃科的胡桃粉（Juglanspollentites)，榆科的榆粉（Ulmipollenites)，椴科的椴粉（Tiliapollenites)等 相似文献
5.
A total of 85 samples, collected from the UBGH1-9 core taken from the Ulleung Basin, East Sea, Korea, were analyzed using diatom assemblages. 111 diatom species belonging to 46 genera were identified, and three diatom assemblage zones were established on the basis of occurrence and distribution pattern of diatoms. Diatom assemblage zone I(134.10–174 m) is characterized by a relatively high abundance of marine species, while the increased number of the brackish species is recorded in diatom assemblage zone II(75–125 m). The assemblage zones IIIa became drastic drop of valve abundances and brackish planktons, whereas it became increase during the IIIb. High Td values which indicate an influence of warm current are recorded both in diatom assemblage zone I and III, and low Td values in diatom assemblage zone II. Analysis of diatom assemblages indicating that the depositional condition moved from oceanic to littoral-neritic environments and that paleotemperature underwent a shift from warm to cold condition at the middle interval, and from cold to warm condition in the upper interval of the UBGH1-9 core. This suggests that the lower(130–162 m) and upper intervals(0–20 m) of the UBGH1-9 core were deposited in the warm current condition(Tsushima Warm Current). 相似文献
6.
Kapesa Lokho D. S. N. Raju R. J. Azmi 《Journal of the Geological Society of India》2011,77(3):252-260
Planktic and benthic foraminifera including uvigerinids are documented from the Upper Bhuban Formation, exposed at Thingdawl
village, Kolasib district, Mizoram. The foraminiferal assemblage is poorly preserved and consists of index fossils useful
for precise biochronology and interpretation of the depositional environment. A total of ten benthic and six planktic foraminiferal
species are described. Six species belong to the genus Uvigerina, four to Ammonia, one species each of Globorotalia, Globigerinoides, Clavatorella, Praeorbulina and two species of the genus Orbulina. Based on lithological and foraminiferal assemblage, middle neritic to upper part of outer neritic paleobathymetry is inferred
for the deposition of this part of the Upper Bhuban Formation. The foraminiferal assemblage suggests late Early Miocene to
early Middle Miocene, (∼16 Ma) equivalent to planktic foraminiferal zones N8-N9 for the Upper Bhuban Formation. 相似文献
7.
G. N. Aleksandrova T. V. Oreshkina P. V. Smirnov A. O. Konstantinov O. B. Kuzmina 《Stratigraphy and Geological Correlation》2017,25(4):419-444
An integrated micropaleontological study of deposits enriched in biogenic silica was conducted on material drilled in the Zyryanka and Uspenka fields of the southwestern Tyumen oblast (Western Siberia). The data obtained on palynology and diatoms allowed the assignment of the Zyryanka Field to the Turtas Formation (lower part of the Chattian Stage of the Oligocene) and the deposits of the Uspenka Field to be dated as Pleistocene. The absence in the Zyryanka Field diatom assemblage of in situ marine taxa and the mass occurrence of freshwater species, gemmuloscleres of freshwater sponges, and zygospores of Zygnematales algae suggest that a nonmarine basin existed in the early Turtas time. A considerable proportion of redeposited diatoms and dinocysts in the Quaternary deposits of the Uspenka Field suggest strong erosional processes during the time of deposition. 相似文献
8.
L. G. Bragina Yu. V. Agarkov N. Yu. Bragin 《Stratigraphy and Geological Correlation》2007,15(3):310-320
Diverse radiolarians (over 70 species) are detected in cherty rocks above the bituminous shale horizon, the marker of anoxic event OAE-2 recorded across the Cenomanian-Turonian boundary in the upper part of the Ananuri Formation of flyschoid deposits, the Lazarevskoe area of the western Caucasus. The radiolarian assemblages studied are comparable in composition with radiolarians from concurrent Cenomanian-Turonian boundary strata in other Mediterranean regions (e.g., in the Crimea and Turkey). The lower radiolarian assemblage includes index species Dactyliosphaera silviae of synonymous Cenomanian zone. Alievium superbum present in the upper assemblage is index species of the relevant Turonian zone. Within the studied flyschoid sequence, sediments indicative of the above event (bituminous shales and cherts) are confined to upper elements of flysch rhythms. 相似文献
9.
A. Yu. Gladenkov 《Stratigraphy and Geological Correlation》2013,21(1):96-106
Diatom algae from the Eocene sediments of the marine Cenozoic section in the Il’pinskii Peninsula, northeastern Kamchatka, are studied. The taxonomic composition of the diatom assemblage is characterized, including rare representatives of oceanic plankton. Correlation with planktonic foraminifer associations found in the section indicates a Middle Eocene (Lutetian) age for the diatoms. These are the first records of Eocene diatoms from the northwestern Pacific rim for which such a correlation has been achieved. 相似文献
10.
《Russian Geology and Geophysics》2007,48(4):361-370
We report results of an integrated study of volcanosedimentary rocks of the Middle-Late Miocene Dzhilinda Formation consisting of the prevolcanic sedimentary Lower Dzhilinda and volcanosedimentary Upper Dzhilinda subformations. The section was studied in three wells drilled near Lake Mukhal (Khoigot paleovalley, Vitim upland). The Dzhilinda sediments contain ubiquitous Alveolophora jouseana (Moiss.) Moiss. typical of Miocene environments. Deposition occurred in two main stages represented by different water (diatoms) and land (spores and pollen) plant communities. The upsection successive changes in diatom species are attendant with changes in pollen and spore assemblages. The K-Ar ages of lavas indicate that the mostly sedimentary lower section of the Dzhilinda Formation deposited between 12 and 14 Ma and the more volcanic upper section, with a lacustrine lens at base, formed at about 10.8–9.5 Ma. The isotope dating of volcanic rocks agrees with the ages inferred from the diatom and spore-pollen analyses. The prevolcanic Lower Dzhilinda subformation deposited during the Middle Miocene climate optimum. The stratigraphy, lithology and facies of sediments suggest that the Dzhilinda deposition was associated with the development of a deep freshwater lake in the conditions of active tectonism and volcanism. 相似文献
11.
12.
Palynological complexes from the coaliferous Talyndzhan and Dublikan formations of the Bureya sedimentary basin are analyzed. The palynological assemblage from the upper part of the Talyndzhan Formation is characterized by dominant gymnosperms largely close to Pinaceae and Ginkgocycadophytus. The content of ferns is insignificant against the background of their relatively high taxonomic diversity. The assemblage is marked by the last occurrence of Staplinisporites pocockii, Camptotriletes cerebriformis, C. nitida, and Cingulatisporites sanguinolentus spores typical of the Late Jurassic palynofloras. The palynological assemblage from the Dublikan Formation is dominated by Pteridophyts representing mainly by Cyathidites and Duplexisporites. In addition to the conifer, the role of Classopollis increased among the gymnosperms in this assemblage. It also includes the first-appearing Stereisporites bujargiensis, Neoraistrickia rotundiformis, Contignisporites dorsostriatus, Duplexisporites pseudotuberculatus, D. rotundatus, Appendicisporites tricostatus, and Concavissimisporites asper. These sporomorphs are characteristic of the Berriasian palynofloras. Thus, the Jurassic-Cretaceous boundary is most likely located between the Talyndzhan and Dublikan formations. 相似文献
13.
14.
Conodonts from the deposits of the Mosolovian Regional Stage (Middle Devonian) of the Voronezh Anteclise are studied on the basis of the data from six boreholes. Three assemblages are recognized. The index species of the lowermost assemblage is Icriodus formosus Naz. The index species of the middle assemblage are I. formosus Naz. and Pseudobipennatus ziegleri Kon. et Kim, as well as I. arkonensis Stauff. and I. jejunus Naz. This assemblage is the most diverse and is recognized in all boreholes. The deposits containing this assemblage correspond to the maximum of the Nara transgression. The upper assemblage is also recognized in all the studied boreholes. Its index species is Ps. ziegleri Kon. et Kim. The Mosolovian Regional Stage is assigned to the kockelianus Zone. The distribution diagrams of species in the most diverse middle assemblage support the hypothesis that, in the southeastern regions of the Voronezh anteclise, the depth was greater than in its western part. The characteristic conodont species are shown in the plates. 相似文献
15.
Sebastiaan W. Rampen Stefan Schouten Ellen C. Hopmans Ben Abbas Anna A.M. Noordeloos Jan A.J. Geenevasen J. Michael Moldowan Peter Denisevich Jaap S. Sinninghe Damsté 《Organic Geochemistry》2009,40(2):219-228
23-Methyl sterols have been reported to be synthesized by a few marine algae, but unambiguous identification of 23-methyl steroids in sediments and petroleum is lacking. We report the presence of 23-methylcholesta-5,22E-dien-3β-ol in 14 out of 106 diatom cultures, thereby showing that diatoms, together with dinoflagellates, may be an important environmental source for such steroids. Synthesis of authentic 23-methylcholestanes showed that their mass spectra are identical to those of 24-methylcholestanes, but that they elute earlier on apolar stationary phases during gas chromatography (GC) analysis. Co-injection of the authentic standards with sediment extracts revealed the presence of these compounds in the Skole unit of the Oligocene Menelite Formation, the Miocene Monterey Formation and the Messinian Vena del Gesso Formation. In addition, we tentatively identified 23,24-dimethyl-27-norcholestanes in some of these sediments. Molecular clock calculations suggest that diatoms are a possible source for 23-methyl steroids in sediments and petroleum from the late Jurassic onwards. 相似文献
16.
The investigation of the exposed middle Miocene strata from Wadi Sudr yielded well-preserved ostracod carapaces. Detailed taxonomic and paleontological studies led to the recognition of 36 ostracod species belonging to 25 genera, 4 species of them were considered new which fully described. Three assemblage biozones were recorded as follows: Actinocythereis spinosa–Actinocythereis hystrix zone, Chrysocythere cataphracta muricata-Cytheretta africana zone, and Disopontocypris schweijeri-Bythocypris tripolensis zone. The recorded biozones were calibrated with the previously studied middle Miocene planktonic foraminiferal biozones on the same samples and also correlated with the Miocene ostracod biozones from the neighboring countries. Our ostracod assemblages present in the lower and upper parts of the studied section (section II) indicated an inner neritic marine environment of moderate energy of currents and rapid sedimentation, while the assemblages in the middle part showed more deeper (outer neritic) environments with low energy of currents and low rate of sedimentation. The palaeobiogeographic distribution of the studied ostracods showed high affinity with the ostracod assemblages of the southern Mediterranean and moderate to low affinities with that of the northern and eastern Mediterranean respectively. The highly ornamented ostracod species with structures on the carapace were recorded from both Northern and Southern Mediterranean, while the smooth ones were found in the Southern Mediterranean only. The highly ornamented species are more widely distributed in both Southern and Northern Mediterranean than the smooth species. This may indicate that the ornamented species are more able to migrate than the smooth ones. 相似文献
17.
广西那艺泥盆系五指山组下段地层研究 总被引：3，自引：0，他引：3
从广西那艺五指山组下段识别出三个晚泥盆世牙形石标准带，自上而下为：混杂上ｃｒｅｐｉｄａ带，混杂中ｃｒｅｐｉｄａ带至ｔｒｉａｎｇｕｌａｒｉｓ带，下ｔｒｉａｎｇｕｌａｒｉｓ带。该段含不少再沉积化石，岩性以灰质拟角砾岩为主夹瘤状灰岩，从而确定其为碳酸盐浊积岩，浊积的时代为法门期ｔｒｉａｎｇｕｌａｒｉｓ带至上ｃｒｅｐｉｄａ带。该段属陆壳上的盆地相，靠近台地斜坡，至少存在两种类型的浊积岩。另外，本剖面尚发现大量微球粒。 相似文献
18.
Upper Cretaceous sediments of the Kanguk Formation exposed in Eidsbotn and Viks Fiord grabens on Devon Island, Nunavut, Canadian High Arctic, yielded 91 fossil marine diatom species and varieties (including indeterminate taxa), representing 41 genera. Excellent preservation of the assemblages was aided by shallow burial, protection in downfaulted linear grabens, and the presence of abundant volcanic material. Planktonic species and resting spores comprise nearly 70% of the diatom assemblage, and provided abundant food resources for the Late Cretaceous Arctic ecosystem. Deposition of the approximately 225 m-thick stratigraphic sequence was predominantly in a shallow marine neritic setting, with an upward progression to interbedded terrestrial deposits of the Expedition Fiord Formation, reflecting a regression and eventual persistence of terrestrial facies into the Early Cenozoic. The Kanguk Formation is widespread across the Canadian Arctic, and diatom biostratigraphy indicates a Santonian–Campanian age for the sequences reported herein, based on the presence of Gladius antiquus in the lowermost strata and occurrence of Costopyxis antiqua throughout the succession. However, Amblypyrgus sp. A and Archepyrgus sp. aff. A. melosiroides, encountered in the lower part of the succession, are known exclusively from the Lower Cretaceous. This may suggest a slightly older age. New information on shallow shelf diatom assemblages from this study is compared to reports on two other Late Cretacous Arctic diatom assemblages. These three sites represent an environmental transect from shallow to distal shelf settings and into the oceanic realm. 相似文献
19.
N. Yu. Bragin 《Stratigraphy and Geological Correlation》2014,22(2):175-189
New data on Middle Triassic radiolarians from the central part of Kotel’nyi Island are discussed. The Triassic section is represented by clays and mudstones with diverse macro- and microfossils, which confirm the presence of lower Anisian, upper Anisian, and upper Ladinian sediments on the island. The lower Anisian Substage 10–15 m thick is composed of clays with ammonoid species Karangatites evolutus. The upper Anisian Substage 20 m thick consists of clays with phosphate concretions and bivalves Daonella sp. cf. D. moussoni Merian, D. americana Smith, ammonoid form Indigirophyllites sp. ex gr. I. spetsbergensis (Oeberg), and radiolarian assemblage with Glomeropyle boreale Bragin. The upper Ladinian Substage 25–30 m thick is composed of clays with phosphate concretions and bivalves including Daonella frami Kittl., ammonoid species Indigirophyllites sp. ex gr. I. oimekonensis Popow, and radiolarian assemblage with Muelleritortis firma (Gorican). The middle Anisian and lower Ladinian substages are missing, which may be explained by the incompleteness of the section. The Middle Triassic section of Kotel’nyi Island is first stratified on the basis of radiolarians, which are supplemented by the data on cephalopods and bivalves. Glomeropyle saccum Bragin, sp. nov. is described. 相似文献
20.
福建永安吉山剖面的再研究 总被引：2，自引：0，他引：2
<正> 1943年陈恺在福建进行地质调查时,将不整合于火山岩之上,赤石群之下的一套河湖相砂页岩统称为坂头系,后人改称为坂头组。标准剖面位于永安市西北约10km之坂头村。1945年斯行健研究了其中所含植物化石,有Ruffordia goepperti,Onychio-psis?sp.,Cladophlebis cf.dunkeri,Sagenopteris yunganensis,S.? dictyozamoides, 相似文献