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Berriasian bio- and magnetostratigraphy and magnetic susceptibility of the Barlya section (Western Balkan Unit, Bulgaria) – preliminary results

Grabowski J., Lakova I., Schnabl P., Sobień K., Petrova S.

Volumina Jurassica

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2014

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Vol. 12, no. 1

185--194

EN

Integrated bio- and magnetostratigraphic data from the Lower to Upper Berriasian of the pelagic succession at Barlya (Western Balkan, Bulgaria) are presented. The investigated interval, 24 m thick, covers the top of the Calpionella elliptica, Calpionellopsis simplex and Calpionellopsis oblonga subzones. Magnetozones from the upper part of M17r up to M16n were identified. The boundary between the Elliptica and Simplex subzones correlates with the lower part of M16r, while the boundary between the Simplex and Oblonga subzones is situated in the lower part of M16n. The magnetic susceptibility reveals an increasing trend from the middle part of M16r which accounts for the increasing supply of fine clastic sediments to the basin.

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Towards a standard Tithonian to Valanginian calpionellid zonation of the Tethyan Realm

Lakova I., Petrova S.

Acta Geologica Polonica

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2013

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Vol. 63, no. 2

201--221

EN

A calpionellid zonal scheme is proposed for the Tithonian through Valanginian pelagic carbonates of the Western Balkan Unit, based on the vertical ranges of 57 chitinoidellid and calpionellid species recognized. This zonal scheme consists of calpionellid zones that are widely accepted in the Mediterranean Realm, such as the zones of Chitinoidella, Praetintinnopsella, Crassicollaria, Calpionella, Calpionellopsis, Calpionellites and Tintinnopsella. Subzonal divisions are comparable to those in the Carpathians. Direct correlations between ammonite and calpionellid ranges suggest that the base of the Upper Tithonian corresponds to the FO of Chitinoidella boneti; that of the Upper Berriasian to the FO of the genus Calpionellopsis; and the base and top of the Lower Valanginian to the FO and LO of the genus Calpionellites respectively. Correlations of the calpionellid zonation in the study area with zonations in other areas are discussed.

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New conodont and palynological data from the Lower Palaeozoic in Northern Camdag, NW Anatolia, Turkey

Boncheva I., Goncuoglu M., Leslie S., Saydam G., Gedik I., Sachanski V., Konigshof P., Lakova I.

Acta Geologica Polonica

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2009

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Vol. 59, no. 2

157-171

EN

Two main thrust slices in the Camdag area (NW Anatolia), were informally named the Southern and Northern Camdag units. New micropaleontological and palynological data about the Ordovician, Silurian and Devonian in the Northern Camdag have allowed a better understanding of the Early Palaeozoic evolution of this critical area between the Istanbul Terrane in the west and the Zonguldak Terrane in the east. The Middle Ordovician age obtained from the conodont-bearing limestone band within the Aydos Formation in this study is in agreement with the data from the Zonguldag Terrane. Acritarch evidence suggests a Late Ordovician age of the upper part of Aydos Formation. This paper concerns the Northern unit. Three members are distinguished in the Findikli Formation and dated biostratigraphically. The lower member (Black Shale Member) of the Findikli Formation is absent from the Kabalak Dere section, but was assigned elsewhere to the Llandovery on the basis of graptolites. The middle member (Shale-Siltstone Member) is dated as Wenlock and Ludlow on the basis of acritarchs. The upper member (Shale-Limestones Member) spans a continuous upper Silurian - Lower Devonian succession. The overlaying Ferizli Formation is assigned to the Middle Devonian on the basis of conodonts. The new stratigraphic data indicate that the Southern Camdag unit corresponds to the Istanbul Terrane and the Northern Camdag unit to the Zonguldak Terrane. The tectonic contact between the Northern and the Southern units is a steep south-verging thrust-fault.

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Facies transition and biostratigraphic correlation of the Upper Silurian and Lower Devonian in West Bulgaria

Boncheva I., Sachanski V., Lakova I., Yaneva M.

Geological Quarterly

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2007

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Vol. 51, No 4

407-418

EN

Upper Silurian and Lower Devonian shelf deposits in West Bulgaria are exposed in three main Alpine tectonic units: the West Balkan Unit, the Lyubash Monocline and the Morava Unit. The West Balkan and Lyubash units consist of siliciclastic deposits: black graptolitic shales, banded pale shales and black siltstones. The Ludlow, Pridoli, Lochkovian, Pragian and Emsian were recognized on the basis of graptolite and tentaculite faunas. In the Morava Unit, the Ludlow black shales are progressively replaced by clayey limestones and nodular and micritic limestones in the Pridoli and Early Devonian. Newly obtained conodonts show the presence of the siluricus, eosteinhornensis, woschmidti, postwoschmidti, delta-pesavis, sulcatus, dehiscens and gronbergi zones. Petrographic study of the Morava Unit shows an increasing carbonate content and shallowing conditions upwards. The biostratigraphical correlation and facies interpretation reveal the coeval existence of two different depositional environments within the same shelf basin as well as a gradual shift in proximal direction.

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Callovian to Berriasian pelagic carbonates in the Western Fore-Balkan, Bulgaria: microfacies, ammonite and microfossil zonations

Ivanova D., Koleva-Rekalova E., Lakova I., Metodiev L.

Volumina Jurassica

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2006

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Vol. 4, no. 1

175-177

EN

The Callovian to Berriasian pelagic carbonates in the Western Fore-Balkan crop out as a part of the Middle Jurassic – Lower Cretaceous peri-platform marine sediments deposited on the northern Tethyan continental margin. This pelagic record consists of marl-limestone alternation (Bov Formation), grey micritic limestones with reddish nodular limestones (Javorets Formation), Ammonitico Rosso type red nodular limestones (Gintsi Formation) and Biancone-type grey micritic regularly bedded limestones (Glozhene Formation) (Sapunov 1976). The total thickness of this succession exceeds 400 m. Rich ammonite faunas recorded from the Bov, Javorets and Gintsi Formations enabled ammonite zonation and age assignment: Macrocephalites spp., Hecticoceras spp. and Kosmoceras spp. zones (Callovian), P. athletoides, C. renggeri, P. (D.) episcopallis, P. (D.) antecedens and G. riazi zones (Oxfordian), H. beckeri zone (Upper Kimmeridgian) and H. hybonotum, S. schwertschlageri and V. rothpletzi zones (Tithonian). The stratigraphic distribution and relative abundance of pelagic microplankton organisms (thin-shelled bivalves, planktonic foraminifers, radiolarians, calcareous dinocysts, pelagic echinoderms and calpionellids) have been used for biostratigraphy and/or recognition of microbiofacies. Within the Oxfordian- Berriasian interval the calcareous dinocyst zones: C. fibrata, C. borzai, C. tithonica, P. malmica, C. tenuis, C. fortis, St. proxima and St. wanneri are recorded. The Middle Tithonian to Berriasian interval is characterized by the successive calpionellid zones: Chitinoidella, Praetintinnopsella, Crassicollaria, Calpionella and Calpionellopsis (Lakova et al. 1999). Five microbiofacies within the pelagic carbonates are superposed: mudstone and wackestone with filaments of pelagic bivalves (Callovian), Globuligerina wackestone and radiolarian wackestone [Oxfordian-Kimmeridgian(?)], Saccocoma wackestones (Kimmeridgian – Lower Tithonian) Globochaete mudstone (Middle Tithonian) and calpionellid mudstone (Upper Tithonian and Berriasian) (Fig. 1). The estimated average rate of sedimentation within the Callovian-Berriasian pelagic succession in the Western Fore-Balkan varying from 9 to 26 mm/10 3 years is characteristic for the transition from relatively condensed to stratigraphically expanded sections in the Upper Jurassic of the Tethyan region. This rate is lower during the Callovian to Kimmeridgian and increased significantly in the Tithonian and Berriasian. Probable explanations are partial carbonate dissolution of the red nodular limestones in the Late Jurassic and the increased bioproductivity of nannoplankton in the Berriasian.