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Early Pliocene calcareous and siliceous microfossils of the Sawai Bay Formation, Car Nicobar Island, northern Indian Ocean

Chakraborty Arindam, Ghosh Amit K., Mccartney Kevin, Saxena Stuti, Dey Rikee, Roy Lopamudra

Acta Geologica Polonica

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2021

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Vol. 71, no. 2

175--198

EN

The present contribution provides a study of calcareous nannofossils and siliceous microfossils from the Sawai Bay Formation on Car Nicobar Island, northern Indian Ocean. Two stratigraphically short sediment intervals near Sawai Bay have been examined. Qualitative and quantitative microfossil analyses show the Sawai Bay ‘A’ Section to be devoid of siliceous microfossils, while 24 well-preserved calcareous nannofossil taxa are identified. The Sawai Bay ‘B’ Section yields 18 calcareous nannofossil, 33 radiolarian and 25 diatom taxa. The calcareous nannofossil index taxa (Ceratolithus armatus Müller, 1974a and C. cristatus Kamptner, 1950) indicate both sections to be from zones NN12 (CN10b) and NN13 (CN10c) of early Pliocene (Zanclean) age. The radiolarian taxa, i.e., Didymocyrtis avita Riedel, 1953, Euchitonia spp., Siphocampe lineata (Ehrenberg) Nigrini, 1977, Stichocorys peregrina Riedel, 1953, Semantis spp. and Stylochlamydium sp. are common in the Sawai Bay ‘B’ Section, which is assigned to Zone RN9. Most of the diatom taxa are represented by rep-resentatives of the genera Actinocyclus Ehrenberg, 1837, Azpeitia Peragallo in Tèmpere and Peragallo, 1912, Coscinodiscus Ehrenberg, 1839a, Grammatophora Ehrenberg, 1841 and Triceratium Ehrenberg, 1839b, with the benthic diatom species Triceratium favus Ehrenberg, 1839b being predominant (~35% of the total diatom count). Siliceous microfossils are also represented by silicoflagellates dominated by Dictyocha spp. and sponge spicules dominated by astrophorids.

2

Biostratigraphy, geochemistry and sedimentology of Middle to Late Jurassic strata in the Strážovce section (Strážovské vrchy Mts), Krížna Nappe of the Central Carpathians, Slovakia

Michalík J., Bąk M., Lintnerová O., Méres Š

Volumina Jurassica

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2017

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Vol. 15, no 1

161--178

EN

The Jurassic / Lower Cretaceous sequence of the Strážovce section has been deposited in the central, axial part of the Zliechov Basin. Its most characteristic part – the Ždiar Formation consists of bedded siliceous radiolarian limestones and radiolarites. The radiolar¬ian assemblage typical of the North Tethyan Bioprovince lived during mid Oxfordian – Early Kimmeridgian in a warm upper part of the well stratified water column, partially near to the thermocline. Radiolarian abundance decreases upwards. Productivity decrease is quanti¬fied by the share of biogenic SiO2 as well as by high EFSi values during sedimentation of both the Ždiar and Jasenina formations. The geochemical data indicate relatively stable volume of the siliciclastic component of the rocks and a felsic character comparable to the Average Shale. The chemically homogeneous sedimentary signal indicates values of both CPA and EF ≤ 1 of Ti, Zr, Fe, Na, K, Rb, V and U. The values of EF > 1 signal enrichment of elements with affinity to carbonate minerals (Sr, Mn, P, Y, and Mg). Metal enrichment (Cu, Zn and Ni) indicates metal mobilization from other sources or due to carbonate diagenesis. In comparison to the Average Shale, decreased ΣREE´s and negative Cech and Euch anomalies could be regarded as a typical deep sea water signal. The differentiated REE record of higher calcareous beds of the Jasenina Fm. suggests basinal dysoxic conditions. The “bell-shape” of curves (normalized to shale) indicate that REEs were slightly affected by carbonate diagenesis. The Oxfordian / Kimmeridgian siliceous sedimentation in the Zliechov Basin was influenced probably more by monsoon-controlled input of land derived weathered material than by hydrothermal fluids from the bottom rifts.

3

The Jurassic-Cretaceous boundary in Boreal Russia : radiolarian and calcareous dinoflagellate potential biomarkers

Vishnevskaya V. S.

Geological Quarterly

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2017

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Vol. 61, No. 3

641--654

EN

The International Berriasian Working Group (ISCS) suggested primary and secondary marker “datums” to fix the basal Berriasian boundary and thus to detine the Jurassic-Cretaceous boundary (Wimbledon et al., 2011, 2013). Two primary markers Calpionella, as well as calcareous nannoplankton, are practically unknown in the Boreal Realm. Testing and calibration of these markers, as well as of fossils of radiolarians and other signals, in the most complete sections, were declared as an important task for the near future. In the Tethys, the Jurassic-Cretaceous boundary based on radiolarians falls inside zone UAZ 13 of Baumgartner et al. (1995), whereas in the palaeo-Pacific it corresponds to the boundary between zones 4 and 5 of Pessagno et al. (2009), and in boreal Siberia it probably falls between the biohorizons of Parvicingula haeckeli and P. khabakovi. The radiolarian events at the Jurassic-Cretaceous boundary in the boreal successions of Russia can be proposed to be used as an additional biomarker to help develop new integrated boundary criteria. Thus, as the first appearance of the zonal species Calpionella alpina, which defines the Jurassic and Cretaceous boundary, coincides with the first occurrence of the calcareous dinocyst zonal species Stomiosphaerina proxima (Reháková, 2000), it is logical to propose a calcareous dinoflagellate, widely represented in the Upper Jurassic-Lower Cretaceous Bazhenovo Formation of Siberia, as a secondary marker.

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Radiolarians of the uppermost Oxfordian (Hypselum Zone) of the Wieluń Upland (central Poland)

Smoleń J.

Volumina Jurassica

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2016

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Vol. 14, no. 1

51–-64

EN

Radiolarian assemblages from the uppermost Oxfordian (Hypselum Zone) deposits of two sections (Katarowa Góra and Bobrowniki) in the Wieluń Upland (central Poland) are studied for the first time. The overall composition of the assemblages is characterized by low taxonomic diversity, with many individuals of spherical morphotypes, with dominance of the family Williriedellidae and Gongylothoracidae, among the nassellarians. The radiolarians show features mostly of the Northern Tethyan fauna. Additionally, more cosmopolitan forms consisting of spumellarians and of cold water representatives of the family Parvicingulidae appear in the middle and upper parts of the Hypselum Zone. This change in the character of the radiolarian assemblages suggests Boreal influences into the Submediterranean basin related to activity of sea currents, which have been stimulated by climatic changes during the latest Oxfordian.

5

Remarks on the Tithonian-Berriasian ammonite biostratigraphy of west central Argentina

Riccardi A. C.

Volumina Jurassica

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2015

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Vol. 13, no. 2

23--52

EN

Status and correlation of Andean ammonite biozones are reviewed. Available calpionellid, nannofossil, and radiolarian data, as well as radioisotopic ages, are also considered, especially when directly related to ammonite zones. There is no attempt to deal with the definition of the Jurassic–Cretaceous limit. Correlation of the V. mendozanum Zone with the Semiforme Zone is ratified, but it is open to question if its lower part should be correlated with the upper part of the Darwini Zone. The Pseudolissoceras zitteli Zone is characterized by an assemblage also recorded from Mexico, Cuba and the Betic Ranges of Spain, indicative of the Semiforme–Fallauxi standard zones. The Aulacosphinctes proximus Zone, which is correlated with the Ponti Standard Zone, appears to be closely related to the overlying Windhauseniceras internispinosum Zone, although its biostratigraphic status needs to be reconsidered. On the basis of ammonites, radiolarians and calpionellids the Windhauseniceras internispinosum Assemblage Zone is approximately equivalent to the Suarites bituberculatum Zone of Mexico, the Paralytohoplites caribbeanus Zone of Cuba and the Simplisphinctes/Microcanthum Zone of the Standard Zonation. The C. alternans Zone could be correlated with the uppermost Microcanthum and “Durangites” zones, although in west central Argentina it could be mostly restricted to levels equivalent to the “Durangites Zone”. The Substeueroceras koeneni Zone ranges into the Occitanica Zone, Subalpina and Privasensis subzones, the A. noduliferum Zone could be equivalent to the Dalmasi Subzone, Occitanica Zone, to lower part of the Boissieri Zone, and the S. damesi Zone could range through the upper part of the Boissieri Zone to the lower part of the Pertransiens Zone. Division of the Substeueroceras koeneni Zone and a precise correlation between the Andean ammonite zones and the international standard require new systematic and stratigraphic studies.

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Integrated stratigraphy of the Middle–Upper Jurassic of the Krížna Nappe, Tatra Mountains

Jach R., Djerić N., Goričan Š., Řeháková D.

Annales Societatis Geologorum Poloniae

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2014

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Vol. 84, No. 1

1--33

EN

Middle-Upper Jurassic pelagic carbonates and radiolarites were studied in the Krížna Nappe of the Tatra Mountains (Central Western Carpathians, southern Poland and northern Slovakia). A carbon isotope stra- tigraphy of these deposits was combined with biostratigraphy, based on radiolarians, calcareous dinoflagellates and calpionellids. In the High Tatra and Belianske Tatra Mountains, the Bajocian and part of the Bathonian are represented by a thick succession of spotted limestones and grey nodular limestones, while in the Western Tatra Mountains by relatively thin Bositra-crinoidal limestones. These deposits are referable to a deeper basin and a pelagic carbonate platform, respectively. The various carbonate facies are followed by deep-water biosiliceous facies, namely radiolarites and radiolarian-bearing limestones of Late Bathonian-early Late Kimmeridgian age. These facies pass into Upper Kimmeridgian-Lower Tithonian pelagic carbonates with abundant Saccocoma sp. The bulk-carbonate isotope composition of the carbonate-siliceous deposits shows positive and negative S C excursions and shifts in the Early Bajocian, Late Bajocian, Early Bathonian, Late Bathonian, Late Callovian, Middle Oxfordian and Late Kimmeridgian. Additionally, the S13C curves studied show a pronounced increasing trend in the Callovian and a steadily decreasing trend in the Oxfordian-Early Tithonian. These correlate with the trends known from the Tethyan region. The onset of Late Bathonian radiolarite sedimenlalion is marked by a decreasing trend in S13C. Increased S13C values in the Late Callovian, Middle Oxfordian and Late Kimmeridgian (Moluccana Zone) correspond with enhanced radiolarian production. A significant increase in CaCO3 content is recorded just above the Late Callovian S13C excursion, which coincides with a transition from green to variegated radiolarites.

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Towards the definition of the Triassic/Jurassic systems boundary

Bloos G.

Volumina Jurassica

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2006

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Vol. 4, no. 1

277-277

EN

This contribution summarizes the main stratigraphic results of the T/J Boundary WG since its establishment in 1988 and of the IGCP Project 458 (2001-2005); state at end of March 2006. The T/J transition in general. It begins with the main end-Triassic extinction event which is related to the negative carbon isotope excursion 13Corg. Above follows a range of strongly impoverished Triassic survivors whose duration is different in different fossil groups. Above begins the succession of Jurassic forms, sometimes at first together with last Triassic forms. Up to now (March 2006) four candidate GSSPs have been proposed: St. Audrie's Bay (Somerset, UK), Muller Canyon (Nevada, USA), Chilingote (Utcubamba Valley, Peru), and Kunga Island (British Columbia, Canada). Further important sections are known; one, situated in the Alps, will be proposed as a fifth candidate. Three possibilities to define the T/J boundary are proposed: 1. within the succession of early psiloceratids (England, Nevada); 2. at the base of the psiloceratid succession (England, Nevada, Peru); 3. at the radiolarian turnover in the T/J transitional interval (Canada). Proposal 1. It is essentially the traditional boundary since the 19 th century, indicated by the first wide-spread occurrence of psiloceratids. Since no psiloceratid species is cosmopolitan, global correlation is possible only by regional species and thus essentially tentative. The proposed correlation Psiloceras planorbis - Ps. calliphyllum - Ps. pacificum is supported by the partly proved, partly probable occurrence of the genus Neophyllites below. Since there is no difference in the associated fossil content below and above the boundary, no proxies are known which could indicate the position of the boundary where ammonites are lacking. In this case only earlier levels are available. Proposal 2. With this proposal all psiloceratids would become Jurassic. The difficulty to distinguish between Triassic and Jurassic psiloceratids would be avoided. A global correlation by ammonites would be more difficult than in "proposal 1" because such early forms are extremely rare, belong to regionally restricted species and are not proved to be coeval. First appearances of Jurassic forms in other fossil groups, particularly in palynomorphs, could be regional proxies for correlations, also with sections where ammonites are lacking. Proposal 3. New investigations suggest that the radiolarian turnover could be a global event and potentially a suitable system boundary. However, successions of sufficiently preserved radiolarians are extremely rare and they are, moreover, poor in other fossils.Therefore, the correlation with other fossil groups is diffcult and, consequently, the exact stratigraphic position of the turnover is not yet known. No proxies of other fossil groups are known to recognize the turnover in sections without radiolarians. The strong impact on the evolution of radiolarians suggests that the radiolarian turnover is close to the main end-Triassic extinction event. In this case the turnover could be situated still in latest Triassic as defined e.g. by surviving Misikella posthernsteini in Britain.

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The Jurassic biosiliceous sediments from the Sicanian basin in Western Sicily: new data

Chiari M., Di Stefano P., Parisi G.

Volumina Jurassica

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2006

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Vol. 4, no. 1

153-154

EN

Detailed stratigraphic analyses on Jurassic radiolarites from centralwestern Sicily provide new data on the onset of the biosiliceous sedimentation in the Sicanian Basin. Studies were performed in two structural units of the Maghrebian chain that crop out south of Corleone, i.e. the Monte Barraců and the Campofiorito units. The radiolaritic unit at Monte Barraců consists of radiolarian-bearing cherty calcilutites alternating with cherts and levels of siliceous marls. The lower zone is green-grey coloured, while the upper one is red. This unit covers uppermost Triassic – Lower Jurassic cherty calcilutites through a large-scale stepped unconformity of submarine origin. The upper boundary (affected, in places, by synsedimentary deformations) is transitional to a thin unit of red wackestones with Saccocoma grading upwards to pink to whitish calpionellid cherty wackestones. The radiolarians from samples collected in the radiolaritic unit (lower zone) indicate a Late Bajocian to latest Bajocian – Early Bathonian age (UAZ. 4-5) for the presence of Ares cylindricus flexuosus (Takemura) and Parahsuum(?) magnum Takemura. The transitional zone between green and red radiolarites contains a radiolarian assemblage which indicates a Middle-Late Oxfordian age (UAZ. 9) for the presence of Emiluvia pentaporata Steiger & Steiger and Saitoum levium De Wever. Samples collected in the uppermost zone yielded Podocapsa amphitreptera Foreman and Hexasaturnalis minor (Baumgartner) that indicate a Middle-Late Oxfordian to Late Kimmeridgian – Early Tithonian age (UAZ. 9-11). In the Campofiorito section the radiolaritic unit covers a 20 m thick unit of basaltic pillow lavas and hyaloclastites, resting in turn on Lower Jurassic cherty calcilutites and marls. The lithologies of the radiolaritic unit are well comparable to the Monte Barraců ones. In this section samples from the basal zone could be dated as Early-Middle Bajocian to Middle Bathonian (UAZ. 3-6) for the coexistence of Paronaella kotura Baumgartner with Unuma echinatus Ichikawa and Yao. In the upper part of the section a poor preservation of radiolarians in the studied samples prevents further biostratigraphic evaluations. The new data fit well the biostratigraphic evaluations already available from the adjacent structural units of Monte Genuardo and Giuliana. They indicate that the onset of the biosiliceous sedimentation, in a large sector of the Sicanian Basin, can be “bracketed” between Late Bajocian and Early-Mid Bathonian times.

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Lower Jurassic radiolarians from the Mt. Camicia – Gran Sasso (Central Apennines, Italy)

Bertinelli A., Marcucci M.

Volumina Jurassica

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2006

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Vol. 4, no. 1

146-147

EN

Mt. Camicia area belongs to the Gran Sasso Range (Central Apennines, Italy). Well-preserved Middle and Late Hettangian radiolarians have been discovered S-E of Mt. Camicia, in limestone beds that contain also Hetangian ammonites (Bertinelli et al. 2004). These beds are part of a carbonate succession, Late Triassic to Early Liassic in age, which crops out in the eastern part of the Gran Sasso Range. This succession includes euxinic deposits (bituminous dolostones) and other deposits with pelagic characteristics (mudstones and calcarenites). All these deposits developed in a shelf basin bounded by a carbonate platform in which, in the same time interval, were originated the well-known formations of Dolomia Principale and Calcare Massiccio. We describe here the radiolarian assemblages collected together with ammonites in three levels in the ammonite bearing beds, belonging to a section on the eastern side of the “Vallone di Vradda” at Mt. Camicia. The ammonites in the lowest level indicate a Middle Hettangian age, those from the two upper levels indicate Late Hettangian. In this paper we define six new radiolarian species [(?)Anaticapitula parvireticulata, (?)Bipedis venturii, Farcus leonseveroi, Parahsuum vraddense, Squinabolella multispinata, (?)Trexus sphaericus], and describe twenty-seven other species, which we do not establish formally. In the Western Tethys successions the Hettangian radiolarians are rare and have been found together with ammonites only in the Mt. Camicia section (Bertinelli et al. 2004). The ammonite-radiolarian association from the Mt. Camicia area permits to correlate radiolarians with ammonite zonation.

10

Jurassic radiolarians from reworked manganese nodules in an oceanic mélange, Argolis Peninsula (Greece)

Chiari M., Baumgartner P., Bernoulli D., Bortolotti V., Marcucci M., Photiades A., Principi G.

Volumina Jurassica

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2006

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Vol. 4, no. 1

40-40

EN

In the eastern Argolis area, the lowermost paleotectonic unit, the Didhimi-Trapezona Basal Series includes Upper Triassic to middle Liassic shallow-water carbonates (Pantokrator Limestone) which formed the western Pelagonian margin bordering an oceanic domain. Drowning of the margin is documented by condensed pelagic limestones of Toarcian to Middle Jurassic age, followed up-section by Upper Jurassic radiolarian cherts that grade into siliceous mudstones with interbedded sandstones rich in volcanic fragments (Dhimaina Fm) documenting the erosion of ophiolites. Up-section the Potami Fm, includes, besides clasts of boninitic affinity, olistholiths of Middle Jurassic siliceous mudstones and shales. The sedimentary structures in the Potami Formation document gravitational emplacement from a nearby source, i.e., from the ophiolites that became obducted onto the Pelagonian margin in Late Jurassic time. During Tertiary, this ophiolite nappe and its basement were involved again in thrusting and nappe formation. Along the road from Angelokastron to Sofiko, 2 km east of Angelokaston a small quarry exposes pervasively sheared, dark reddish-brown, radiolarian-bearing cherty shales occurring in the footwall of a thrust bringing them into contact with the Pantokrator Limestone. Across the shales, manganese nodules, 5 to 15 cm in diameter and with a nucleus of radiolarian chert, are irregularly scattered. Several manganese nodules and several chert samples from the siliceous shale matrix were collected for radiolarian biochronological analyses. One nucleus of a manganese nodule yielded a well-preserved Liassic radiolarian assemblage with Pseudoheliodiscus alpinus Kozur & Mostler, Thurstonia magnaglobus Whalen & Carter, Paronaella ravanensis Whalen & Carter and Praehexasaturnalis poultoni Whalen & Carter. This assemblage indicates a Hettangian age. In contrast, several chert nodules from the siliceous shale matrix, yielded Middle Jurassic radiolarian assemblages. Sample GR 62F from a red chert, collected in the siliceous matrix, yielded: Palinandromeda sognoensis Baumgartner and Parahsuum(?) natorense El Kadiri; this assemblage indicates an Early-Middle Aalenian to Early-Middle Bajocian age (UAZ. 1-3). Sample GR 61 from a red chert, collected in the siliceous matrix, yielded: Striatojaponicapsa plicarum ssp. A , Tricolocapsa(?) fusiformis Yao with Eucyrtidiellum unumaense dentatum Baumgartner, Stylocapsa oblongula Kocher and Zhamoidellum ventricosum Dumitrica; this assemblage indicates a Middle Bathonian age (UAZ. 6). We suggest that the Liassic manganese nodules with their cherty cores, certainly more consolidated than their original matrix, became exhumed on the slope of an intra-oceanic accretionary wedge, were redeposited at its toe and embedded in a Middle Jurassic siliceous mudstone matrix, probably on the floor of the Early-Middle Jurassic Vardar Ocean. During the westward advancement of the east-directed Vardar subduction, the mudstones were incorporated into the prism and were finally emplaced as olistholiths on the Pelagonian margin during the Kimmeridgian, shortly before the Vardar obduction onto the Pelagonian margin.

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Integrated stratigraphy (radiolarians and calcareous nannofossils) of the Middle to Upper Jurassic Alpine radiolarites (Lombardian Basin, Italy):constraints to a genetic interpretation

Chiari M., Cobianchi M., Picotti V.

Volumina Jurassica

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2006

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Vol. 4, no. 1

152-153

EN

New biostratigraphic data obtained by integrating radiolarian and calcareous nannofossil stratigraphy document a depositional history for the Middle to Upper Jurassic radiolarites of the Southern Alps characterized by strong fluctuations in the sedimentation rates, associated with shifts from turbiditic to hemipelagic sedimentary processes. The radiolarites were studied in four sections located in different settings of the Lombardian Basin, a rifted basin of the northern Adriatic Plate, where this interval is known as Selcifero Lombardo Formation. The latter consists of two members, the Radiolarite and the Rosso ad Aptici, respectively, and passes, gradually, upwards to the Maiolica Formation. The sections studied were sampled in detail to obtain data on their lithology (using facies and microfacies analyses and calcimetry) and their nanno- and microfossils content (especially radiolarians, and calpionellids). An almost complete record of radiolarians was detected throughout the Selcifero Lombardo Formation, so that the Radiolarian Zonation (UAZones) for the Middle to Upper Jurassic interval, partially integrated with calcareous nannofossils and calpionellid biostratigraphic data, was successfully applied. Accordingly, the Radiolarite unit correlates with the Lower Bathonian (UAZ. 5) to the Kimmeridgian (UAZ. 11) interval, and the Rosso ad Aptici member displays an age spanning from Kimmeridgian to the base of Upper Tithonian (from the UAZ. 10-11 to nannofossil NJK zone). The base of the Maiolica Formation is assigned to Upper Tithonian, in agreement with the previous authors. We interpret the radiolarites as pelagic sediments relatively enriched in radiolarian during a long time span of basin starvation, due to the near absence of periplatform exportation. Because the very low sedimentation rates equally imply low radiolarian productivity, it is not necessary to claim for high water fertility during Middle to Late Jurassic, even if this latter condition likely played a role in development of the carbonate platforms.

12

Early Hettangian ammonites and radiolarians from the Queen Charlotte Islands (British Columbia, Canada) and their bearing on the definition of the Triassic/Jurassic boundary

Longridge L., Carter E., Smith P., Tipper H.

Volumina Jurassica

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2006

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Vol. 4, no. 1

290-290

EN

The extinction that marks the Triassic/Jurassic boundary (T/J boundary) is one of the so-called "big five" that punctuate the Phanerozoic. Two sequences spanning the boundary occur in the Queen Charlotte Islands (QCI) of British Columbia; one is located at Kennecott Point on Graham Island (section I), the other on the southeastern shore of Kunga Island (section III). A second section at Kennecott Point contains fossils of Early Hettangian age only (section II). Eleven ammonite taxa are present in the Lower Hettangian sections of the QCI. Ammonite faunas indicate an Early Hettangian age for the upper portion of section I and permit correlation of the upper portion of section II with the middle Lower Hettangian Minutum Zone. Section III contains moderately diverse Early Hettangian ammonites that allow correlation of the lower portion of the section with the Minutum and Pacificum zones and the upper portion with the upper Lower Hettangian Polymorphum Zone. Lower Hettangian radiolarians from the Canoptum merum Zone are present in all three sections; a few Upper Rhaetian holdovers from the Globolaxtorum tozeri Zone are also present in sections I and II. The T/J boundary radiolarian faunas correlate closely with those in the Inuyama area of Japan indicating that radiolarians were globally distributed at that time. Although ammonite preservation is poor, radiolarian preservation is excellent and the turnover combined with continuous deposition and lack of facies changes over this interval marks the most distinct boundary level currently recognized worldwide. Section I has also produced a carbon isotope curve which records a prolonged negative excursion spanning the T/J boundary while section III has provided a U-Pb date of 199.6±0.3 Ma which constrains the boundary. The latter section has already been proposed as a potential basal Hettangian Global Stratotype Section and Point (GSSP). Although all three QCI sections lack ammonites from the basal Hettangian Spelae ammonite Zone, sections I and III have both yielded earliest Hettangian radiolarian collections which contain Rhaetian holdovers suggesting an approximate correlation of the lower portion of these sections with the Spelae Zone. A section in New York Canyon, Nevada has also been proposed as a potential GSSP. This section provides a virtually complete ammonoid succession but lacks geochronology and microfossils. In essence, the sections at Kunga Island and New York Canyon are complementary. Close correlations between the two sections are possible using ammonite faunas as well as the negative carbon isotope anomalies which span the T/J boundary in Nevada and at Kennecott Point. We suggest the section from Nevada be designated as holostratotype (and datum) for the basal Hettangian and the QCI section be designated as a parastratotype to improve recognition of this interval.

13

Aalenian carbon-isotope stratigraphy: a tool for the ammonite radiolarian and nannofossil zonation calibrations in the Western Tethys

Sandoval J., Aguado R., Bartolini A., Bill M., Bruchez S., O'Dogherty L., Perilli N.

Volumina Jurassica

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2006

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Vol. 4, no. 1

212-213

EN

Here we report a detailed carbon-isotope stratigraphy for the Aalenian (Middle Jurassic) pelagic carbonates in the Betic Cordillera (southern Spain), which represents an ideal region to directly tie the stable carbon-isotope curves to ammonite zones and subzones, and thereby for the first time achieve an accurate chronostratigraphic calibration. For this purpose we have selected two sections (Agua Larga in the province of Granada and Cerro de Mahoma in the province of Murcia) which represent basinal deposits of the southern Iberian palaeomargin. In these sections ammonite are common and relatively wellpreserved. Biostratigraphic analyses enable the recognition of the uppermost Toarcian (Aalensis Zone), the complete Aalenian (Opalinum, Murchisonae, Bradfordensis and Concavum zones) and the lowermost Bajocian (Discites Zone). Calcareous nannofossils and radiolarians (at discrete beds of the Upper Aalenian - Lower Bajocian) are also common in these Median Subbetic hemipelagic sections. The Subbetic Aalenian is characterized by a monotonous and rhythmical alternance of marlstones and marls in continuous sedimentation throughout the analysed interval. We present a ?13C curve very detailed (bed by bed) for the uppermost Toarcian - lowermost Bajocian interval. The curve shows a relative minimum (around 1‰) in the Upper Toarcian, a weak positive shift (around 2‰) in Lower Aalenian (Comptum Subzone), a decreasing values (newly around 1‰) in the Middle Aalenian (Bradfordensis Zone), a positive peak of 2.7‰ in the Upper Aalenian (Concavum Zone and Subzone) and a new relative minimum (1.5-1.7‰) at Aalenian/Bajocian boundary. A good correlation among the isotope curve and the different biostratigraphic zonations is accurately presented. We explore the powerfulness of this well-calibrated ?13C curve as a tool for stratigraphic correlation. In this sense, the biochronostratigraphic position of the radiolarian UAzones 1-2 (mainly based on Italian sections with scarce record of ammonites, Baumgartner et al. 1995) are here redefined by means of the isotope reference curve of the Subbetic. We present the results of a biostratigraphic study of nannofossils assemblages throughout the studied interval. In addition, on the base of a semiquantitative study, we have selected the most abundant taxa (>10%) from the whole assemblage to perform a multivariate analysis (principal components): Biscutum dubium, B. intermedium, Crepidolithus crassus, Carinolithus superbus, Discorhabdus striatus, Schizosphaerella spp., Watznaueria contracta and the genus Lotharingius. This multivariate analysis reveals a strong correlation between the abundances of oligotrophic (C. crassus and Schizosphaerella spp.) and eutrophic (B. dubium and B. intermedium) taxa and the fluctuation of the C degree curve.

14

Mid-Cretaceous spicule-rich turbidites in the Silesian Nappe of the Polish Outer Carpathians : radiolarian and foraminiferal biostratigraphy

Bąk M., Bąk K., Ciurej A.

Geological Quarterly

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2005

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Vol. 49, No. 3

275--290

EN

Spicule-rich turbidites are widespread in mid-Cretaceous deep-water flysch of the Subsilesian and Silesian units in the Polish Outer Carpathians. The spicule-richmaterial with an admixture of numerous radiolarian and foraminiferal particles was supplied, together with siliciclastic material, from shallow environments, mostly from the northern margin of the Carpathian Basin. We present new data on the age of these deposits in the Silesian Nappe, where they are distinguished as the Mikuszowice Cherts. This unit is composed of mediumand thick-bedded siliciclastic to calcareous turbidites including bluish cherts in their middle and upper parts and of thin non-calcareous hemipelagic shales.We have studied radiolaria and foraminifera from hemipelagic sediments and spicule-rich turbidites, from two continuous sections in the Barnasiówka Range (BeskidWyspowyMts.) that included theMikuszowice Cherts (31 m thick) and their transition into the surrounding units. The age of the Mikuszowice Cherts was determined taking into account the following radiolarian datum events: (1) the occurrence of Praeconocaryomma lipmanae in the entire unit, (2) the FO (first occurrence) of Hemicryptocapsa tuberosa in the upper part of the unit, (3) the FO of Amphipyndax stocki close to the upper boundary of the unit, (4) the FO of Hemicryptocapsa prepolyhedra in the lowermost part of the overlying Barnasiówka Radiolarian Shale Formation. These datum events appear successively in theWestern Tethys successions within the Rotalipora cushmani planktonic foraminiferal Zone, which corresponds to the middle and upper Cenomanian (except for its uppermost part). The foraminiferal assemblages, in which such taxa as Rotalipora cf. cushmani, R. cf. greenhornensis, whiteinellids and Uvigerinammina praejankoi successively appear, confirm the mid-late Cenomanian age of the spicule-rich turbidites in the Silesian Nappe.

15

Ammonite-supported microfossil and nannoconid stratigraphy of the Tithonian-Hauterivian limestones in selected sections of the Branisko Succession, Pieniny Klippen Belt (Poland)

Pszczółkowski A., Myczyński R.

Studia Geologica Polonica

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2004

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Vol. 123

133-197

EN

The studied sections of the Tithonian-Hauterivian deposits of the Branisko Succession in the Polish part of the Pieniny Klippen Belt (Figs 1-7) yielded micro-, nanno- and macrofossils, which allowed to elaborate more detailed stratigraphy of these strata, especially in the lowermost Cretaceous interval of the Pieniny Limestone Formation. The calpionellids, radiolarians and other microfossils (mainly calcareous dinoflagellate cysts) were studied in thin sections, whereas the calcareous nannofossils were analysed under SEM. The Berriasian-Hauterivian ammonites are described and illustrated. In the Kapuśnica I section, the Upszar Limestone Member of the Czorsztyn Limestone Formation seems to be exclusively of Tithonian age. At present, the Upper Tithonian deposits of the Crassi- collaria Standard Zone are missing in the studied section. In the Łysonka Klippe, the Lower Berriasian limestones are subdivided on the basis of the Nannoconus assemblages. The ammonites of the Jacobi Zone occur in the limestones of the N. steinmannii steinmannii Zone. In the Kapuśnica I section, the sedimentation rate of the limestones assigned to the Elliptica Subzone was about 1.3 m/Ma. The Oblonga Subzone (sensu lato) coincides with the marly deposition episode in this section; the Łysonka Marl Bed is assigned to the lower interval of this subzone. However, the overall sedimentation rate during the Late Berriasian Oblonga Subzone was low (about ~1.7 m/Ma). Presence of the ammonite Tirnovella otopeta Zone was documented in the Kapuśnica II and Łysonka sections. In the Kapuśnica II section, the minimum value of sedimentation rate of the radiolarian-calpionellid limestones assigned to the Lower Valanginian Calpionellites Zone is about 4.1 m/Ma. The Tintinno- psella Zone of the uppermost Lower Valanginian-Hauterivian is represented by a limestone succe- ssion about 51 m thick. In the Łysonka section, the Upper Valanginian limestones of this zone are probably older than those exposed in the Zaskale section. In the latter section, some ammonites are indicative for the Upper Valanginian Criosarasinella furcillata Zone. In the upper part of the Kapuśnica II section, the limestones of the Tintinnopsella Zone yielded Olcostephanus sp. and Neolissoceras desmoceratoides (Wiedmann) found 4.5 m below the top of this section. These ammonites indicate the Early Hauterivian age of the sparsely fossiliferous limestones. The Upper Hauterivian deposits may be represented in the topmost limestones of the Kapuśnica II section.

16

Badenian radiolaria in the Polish part of the Carpathian Foredeep

Barwicz-Piskorz W.

Biuletyn Państwowego Instytutu Geologicznego

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1999

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nr 387

90--91

17

Mikrofauna oksfordu w północno-wschodnim obrzeżeniu Górnośląskiego Zagłębia Węglowego

Smoleń J.

Biuletyn Państwowego Instytutu Geologicznego

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1998

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nr 378

207-223

PL

W wapieniach gąbkowych i marglistych oksfordu dolnego oraz wapieniach cienkopłytowych niższej części oksfordu środkowego, wyróżnionych w rejonie Częstochowa-Zawiercie stwierdzono występowanie licznej mikrofauny. Oznaczono zespół otwornic z indeksowymi gatunkami Spirillina tenuissima Gumbel i Paalzowella feifeli seibaldi Lutae. Na przełomie poziomów Cardioceras bukowskii i C. excavatum wyróżniono horyzont z radiolariami, które miejscem występują w dużym nagromadzeniu, a ich występowanie świadczy o silniejszym wpływie morza Tetydy w tym okresie.

EN

In the sponge and marly limestones of the Lower Oxfordian and in the thin-platy limestones of the lower part of the Middle Oxfordian, distinguished in the Częstochowa-Zawiercie region, the presence of abundant microfauna was stated. The foraminifer assemblage was determined, with the index species Spirillina tenuissima Gumbel and Paalzowella feifeli seiboldi Lutze. In turn of the Cardioceras bukowskii and C. excavatum zones one distinguished the horizon with radiolarians, which locally occur as large accumulations and their presence evidences a stronger influence of the Tethys sea in that period.