Biostratigraphy and magnetostratigraphy of the uppermost Tithonian–Lower Berriasian in the Theodosia area of Crimea (southern Ukraine)

Abstract

We present evidence for the uppermost Jurassic–lowest Cretaceous interval in Crimea, coastal southern Ukraine. Three facies zones are distinguished in the upper Dvuyakornaya and the Mayak formations of the eastern Crimean Peninsula: basinal, slope and toe-of-slope zones. In this interval we identify the lowest Berriasian Jacobi and Grandis subzones of authors, in expanded form, exceeding 160 metres in thickness. We present new magnetostratigraphic interpretations, and identify two normal and two reversed polarity intervals, assigned to M19n, M18r, M18n and M17r, with M19n2n, M19n1r and M19n1n identified in the uppermost Dvuyakornaya Formation. In the Mayak Formation we record the top of M19n.1n, with M18r, M18n and a thick M17r above. In these two formations component calpionellid species have been identified which characterise the Alpina, Ferasini and Elliptica subzones (Calpionella Zone). In M19n, the FADs of the calcareous nannofossils Hexalithus strictus, Cruciellipsis cuvillieri, Nannoconus wintereri, N. steinmannii minor and N. kamptneri minor are found, which is consistent with other Tethyan regions. N. steinmannii steinmannii and N. kamptneri kamptneri first appear in M18r at Ili Burnu. Specimens of the apparently Tithonian foraminiferan index Anchispirocyclina lusitanica are found, but in the Berriasian lower Mayak Formation.