Upper Jurassic – Lower Cretaceous limestones from the easternmost Getic Carbonate Platform (Southern Carpathians, Romania). Microfacies, microfossils and depositional environments

Carbonate deposits from the easternmost part of the Getic Carbonate Platform form good quality outcrops in the Postăvaru and Piatra Mare Massifs (Patrulius 1976). The average thickness of the carbonate succession reaches 400 m in these areas (Patrulius 1976). In the Postăvaru Massif, the Mesozoic succession consists of Upper Jurassic−Lower Cretaceous carbonate deposits which are covered by upper Albian−Cenomanian Conglomerates (Săndulescu 1964). In the Piatra Mare Massif, the carbonate succession comprises Callovian−Berriasian olistoliths which are embedded in the general mass of the upper Aptian Conglomerates (Săndulescu et al. 1972).

  We collected approximately 600 limestone samples from various sections, in the Postăvaru and Piatra Mare Massifs.

The following sections are located in the Postăvaru Massif: Valea Dragă, Drumul Albastru, Larga Mare, Vârful Postăvaru, Muchia Cheii-Trei Fetițe, Trei Fetițe-Poiana Secuilor, Trei Fetițe-Cabana Postăvaru.

Detailed sampling was performed in the Piatra Mare Massif, in the following sections: Bunloc Est, Bunloc Vest, Cariera Bunloc, Cheile Baciului, Cabana Piatra Mare, Valea Gârcinului, Șura de Piatră, Șura de Piatră-Vârful Piatra Mare, Piatra Scrisă, Coada Pietrei Mari, Șirul Stâncilor, Peștera de Gheață, Prăpastia Ursului and Tamina.

The following facies associations were identified: bioclastic intraclastic grainstone/rudstone, coral-microbial boundstone, packstone to floatstone with pelagic microfossils, bioclastic packstone-grainstone, peloidal oncoidic packstone-grainstone, bioclastic grainstone with black pebbles, wackestone with cyanobacteria nodules, fenestral wackestone, non-fossiliferous mudstone.

 

The micropaleontological association contains dasycladalean algae [Salpingoporella pygmea (Gümbel), Petrascula bursiformis Etallon, Aloisalthella sulcata (Alth), encrusting organisms [Bacinella type structures, Crescentiella morronensis (Crescenti), Koskinobulina socialis Cherchi & Schröder, Radiomura cautica Senowbari-Daryan & Schäfer, Perturbatacrusta leini Schlagintweit & Gawlick, Taumathoporella parvovesiculifera (Raineri)], foraminifera [Bramkampella arabica Redmond, Coscinoconus alpinus (Leupold), Coscinoconus delphinensis (Arnaud-Vanneau et al.), Coscinoconus sagittarius (Arnaud-Vanneau et al.), Frentzenella involuta (Mantsurova), Protopeneroplis striata Weynschenk, Protopeneroplis ultragranulata Gorbatchik] and pelagic microorganisms (Calpionella alpina Lorenz).

The identified microfacies types indicate that carbonate material was deposited in two distinct depositional settings. The first one includes slope to basin areas while the second one comprises inner platform depositional environments. The presence of abundant C. alpina and various representatives of the genus Coscinoconus (C. delphinensis, C. sagittarius) indicates that deposition continued in the area at least until the lower Berriasian.  

Acknowledgements

This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0456, within PNCDI III

 References  

Patrulius D (1976) Upper Jurassic−Lower Cretaceous carbonate rocks in the eastern part of the Getic Carbonate Platform and the adjacent flysch troughs. In: Patrulius D, Drăgănescu A, Baltreș A, Popescu B, Rădan S (eds) Carbonate Rocks and Evaporites-Guidebook. International Colloquium on Carbonate Rocks and Evaporites, Guidebook Series 15, Institute of Geology and Geophysics, Bucharest, pp 71-82

Săndulescu, M., 1964. Geological structure of the Postăvarul-Runcu Massif (Brașov Mountains) (in Romanian). Anuarul Comitetului Geologic, 34 (2): 382–422.

Săndulescu M, Patrulius D, Ștefănescu M (1972 a) Geological Map of Romania, scale 1:50 000, Brașov Sheet, 111 a (in Romanian). Institutul Geologic, București