Early Sarmatian paleoenvironments in the easternmost Pannonian Basin (Borod Depression, Romania) revealed by the micropaleontological data

Abstract

Abstract:The Sarmatian sedimentary record of the Borod Depression (eastern Pannonian Basin) consists of a marine sequence with continental influence. The investigated section, located near Vârciorog, was biostratigraphically and paleoenvironmentally analysed. The micro-and macrofossil assemblages include dasycladaceans, characeans, foraminifera, molluscs, polychaetes, ostracods, crabs, bryozoans, fish and vertebrate remains, which are characteristic for a shallow marine setting with local transitions to continental facies. The microfossil assemblages are characteristic for the Elphidium reginum Zone and Mohrensternia Zone of the early Sarmatian (Serravallian). The succession of populations correlates with the sedimentological trend, allowing the separation of several genetic units. The relative sea-level changes and the progradational trend from the top of the section suggest active tectonics in the hinterland (Apuseni Mountains). The shallow seas surrounding the emerging islands (Apuseni Mountains) provided the connections between the Pannonian and Transylvanian basins during the early Sarmatian.Key words: Sarmatian (late Middle Miocene), Borod Depression (NW-Romania), paleoenvironments, paleogeography, sequence stratigraphy, molluscs, bryozoans, foraminifera, ostracods. most representative. Here, we document the micropaleontological record and discuss the detected paleoenvironmental changes in order to restore a part of the paleogeographical evolution at the eastern border of the Pannonian Basin. Material and methodsForty-three samples were collected from fine-grained siliciclastic intervals along the ~9 m thick section, at distances between 5 to 20 cm (Fig. 2). All the samples were processed by standard micropaleontological methods. The microfossils were recovered from the 63 µm sieve fraction after washing 250 g of dried sediment from each sample. Identification of taxa was followed by quantitative analyses of foraminifera based on percentage distribution of different groups (Fig. 4). Representative taxa are documented by stereomicroscope and the scanning electron microscope (SEM) photographs inserted in Figures 5 to 10. ResultsThe microfossil assemblages were interpreted from the biostratigraphic and paleoecological points of view, trying to point out their relationship to the relative sea-level changes

Palaeoecology and sedimentology of the Miocene marine and terrestrial deposits in the “Medieval Quarry” on Devínska Kobyla Hill (Vienna Basin)

“…The 86 Sr/ 87 Sr ra tio from the up per most part of the Sandberg sec tion also in di cates a Sarmatian age of 12.7 Ma (Fordinál et al, 2014). The age of the Sarmatian trans gres sion and re lated fau nal as sem blage turn over (BSE) in the Cen tral Paratethys have been treated by Harzhauser and Piller (2004a, b), Filipescu (2004), Gebhardt et al (2009), Tóth et al (2010, Koubová and Hudáèková (2010) and Filipescu et al (2014), using var i ous ap proaches.…”

The functional significance of the spinose keel structure of benthic foraminifera: inferences from <i>Miliolina cristata</i> Millett, 1898 (Miliolida) from northeast Romania

“…The higher species richness and the abundance of miliolids, which are conspicuously rare in brackish lagoons (Murray, 1968(Murray, , 2006, represented by the genus Cycloforina in assemblages II and IV, indicate increased salinity. Thus, the sediment represented by these foraminiferal assemblages was probably deposited under shallow-water conditions with normal-marine salinity with possible slight fluctuations (compare Filipescu et al, 2014;Roozpeykar and Maghfouri Moghaddam, 2015). Assemblage V, represented only by planktonic species (Globigerina bulloides d'Orbigny and Globorotalia miocenica Palmer), displays normal-marine salinity (Hemleben et al, 1989).…”

The evolution of the Carpathian Foredeep Basin during the latest Badenian and Sarmatian (Middle Miocene): inferences from micropalaeontological data

“…By conrast, the Sarmatian of the Cen tral Paratethys is com monly viewed as more re stricted with mostly brack ish con di tions (Papp, 1954(Papp, , 1956Papp et al, 1974). How ever, some au thors (Filipescu et al, 1999(Filipescu et al, , 2014Piller and Harzhauser, 2005;Corneé et al, 2009) sug gest the ex is tence of nor mal sa lin ity dur ing the Sarmatian.…”

“…In gen eral, Am mo nia beccarii is com monly re garded as an op portu nis tic spe cies which can tol er ate sa lini ties from 10-30‰ (Murray, 2006), be ing able to adapt to hyposaline con di tions (Murray, 1968). Its pre dom i nance or the low di ver sity as so ci ation marked by the dom i na tion of this spe cies usu ally in di cate shal low and brack ish en vi ron ments (Cimerman and Langer, 1991;Hay ward and Hollis, 1994;Filipescu et al, 2014). In the brack ish Ho lo cene de pos its of the NW Black Sea, as in the coastal re gions, where the sa lin ity is 7-8‰, Am mo nia beccarii is the dom i nant spe cies, pro duc ing monospecific as sem blages (Briceag and Ion, 2014).…”

“…Still very shal low but, al most nor mal ma rine sa lin ity con di tions are as so ci ated with As sem blage I, recorded in the Ro ma nian and Moldavian parts stud ied of the ECFB, which is char ac ter ized by the pres ence of elphidiids [espe cially the large-keeled Elphidium spe cies (E. reginum and E. aculeatum)], char ac ter iz ing depths from 0-50 m (Murray, 2006;Gedl et al, 2016). More over, this as sem blage may in di cate gen er ally oligotrophic con di tions and a rich sea-grass veg e tation sub strate (Langer, 1993;Tóth and Görög, 2008;Koubová and Hudáèková, 2010;Zilinska et al, 2010;Filipescu et al, 2014). Shal low, euphotic con di tions of a nor mal ma rine sa lin ity en vi ron ment (Murray, 2006;Peryt and Jasio nowski, 2012) are also cor re lated with foraminifer As sem blage VI, iden ti fied in the FH 3 P 1 Rãdãuïi, Dorneºti and Ripiceni sec tions.…”