Lower Maastrichtian inoceramid bivalves from the Oslen Krivodol section (Western Fore-Balkan, Bulgaria)

Abstract

Inoceramid data were used to characterize the lower Maastrichtian strata in the Western Fore-Balkan (Bulgaria), based on the newly discovered Oslen Krivodol section. The upper part of the Kunino Formation yielded a well-defined inoceramid-bearing level. A number of characteristic taxa make up the inoceramid assemblage, including Cataceramus palliseri (Douglas, 1942), C. subcircularis (Meek, 1876), C. barabini (Morton, 1834), C. glendivensis Walaszczyk, Cobban and Harries, 2001 and Endocostea typica Whitfield, 1880. Additionally, Trochoceramus spp. and “Inoceramus” sp. were also found. It is, therefore, assumed that both the Endocostea typica Zone and an undetermined (probably lower) part of the Trochoceramus radiosus inoceramid Zone are present in the section. It is also assumed that there is a mixing of faunas due to low sedimentation rates and local submarine washout.

Dinoflagellate cyst biostratigraphy of the upper Campanian–lower Maastrichtian interval in the Oslen-Krivodol section, Northwest Bulgaria: preliminary results

“…Strontium isotope stratigraphy indicated the CMB at a value of 0.707728±0.000004, at 3.15 m above the base of the section (Wagreich et al, 2023). The collected inoceramid taxa are characteristic of the lower Maastrichtian interval (Dochev et al, 2023).…”

“…The succeeding Kunino Formation (over 4.5 m) is represented by thin-to medium bedded limestones, clayey and nodular limestones, overlied by the nodular limestones, typically rich in flint nodules of the Mezdra Formation (not logged) (Fig. 1b) (Dochev et al, 2023). In our ongoing research, these sediments are studied for calcareous nannofossils, dinoflagellate cysts and inoceramid bivalves, and belemnite rostra are used for strontium isotope stratigraphy.…”