Key problems of stratigraphy in the Eastern Crimea Peninsula: some insights from new dating and structural data

Abstract

The tectonic evolution of the Eastern Black Sea Basin has previously been explained based on offshore and onshore data, some of the latter from the Crimean Mountains (CM). However, changes in the stratigraphy of the CM have recently been proposed: the Late Triassic–Early Jurassic Tauric Group was assigned as younger (Albian). To clarify the stratigraphy and the tectonic evolution of this area, we sampled the eastern CM for micropalaeontological datings (nannoplankton). The results demonstrate an Early Cretaceous age for the Tauric Group in the eastern CM. The samples contained substantial amounts of volcanic ash, indicating a period of magmatic activity along all the eastern CM. Our field observations allowed us to propose a new structural map and cross-sections, using which three main tectonic units were distinguished. We define a phase of extension during the Early Cretaceous and one of shortening during the Paleocene–Early Eocene, before the main Middle Eocene limestone unconformity. These two phases are related to: (1) the opening of the Eastern Black Sea Basin along NNW–SSE-trending normal faults and the associated magmatism; and (2) north–south shortening that could be comparable with the inversion in Dobrogea and/or with north–south shortening linked to the collision of continental blocks in the Pontides and Taurides domains.

The position and age of flysch deposits in the Crimean Mountains (Southern Ukraine).

“…A thin-sec tion of the same sam ple also re veals the pres ence of Up per Ju ras sic foraminifera. Ad di tion ally, from the same lo cal ity (Bere hove/Kas tro pol, sam ple 40 lo cated at 225 m, az i muth 75 from WP 39), Sheremet et al (2016a) re ported the pres ence of Hauterivian-Early Barremian cal car e ous nannoplankton. Early Cre ta ceous (Up per Valanginian-Lower Barremian) cal car e ous nannoplankton has also been doc u mented in a sam ple from Yalta (Sheremet et al, 2016a:, sam ple 42).…”

“…The age of this for ma tion is Lower Cre ta ceous, not youn ger than Valanginian (Sheremet et al, 2016a). (Figs.…”

“…How ever, these re sults have not been cor re lated with any lithostratigraphic units shown in geo log i cal maps (Pivovarov and Derenyuk, 1984;Bilecki, 2006a, b;Yudin, 2009) and, more over, sam ples col lected from the un ques tion able TFF de pos its have been usu ally bar ren. In an other pub li ca tion, Sheremet et al (2016a) give ad di tional micropalaeontological data (e.g., from Berehove and Yalta) and pro vide a new in ter pre ta tion of the struc tural evo lu tion of the CM (Fig. 3).…”

“…This age has been chal lenged by Popadyuk and Smirnov (1991), who con cluded Early Cre ta ceous age. This sparked a lively dis cus sion (e.g., Popadyuk et al, 2010Popadyuk et al, , 2013aPopadyuk et al, , b, 2014Oszczypko et al, 2012b, c) un til Sheremet et al (2014Sheremet et al ( , 2016a, on the ba sis of cal car e ous nannoplanton anal y ses of flysch-like de pos its in the east ern sec tor of the CM, in cluded both the Tauric For ma tion and the Lower Cre ta ceous flysch de pos its of the east ern sec tor of the Cri mea into the Tauric Group.…”

“…These stud ies showed that the moun tain range ex pe ri enced a ther mal over print af ter the Late Cim mer ian orog eny: at least 4 km of burial by the Early Cre ta ceous/Late Eocene plat form was fol lowed by Mid dle Plio cene up lift, flu vial ero sion and large -scale land slides. Sheremet et al (2014Sheremet et al ( , 2016a, based on new micropalaeontological data, pro posed Up per Tri as sic to Mid dle Juras sic and Lower Early Cre ta ceous ages of the Tauric Group in the east ern CM, as so ci ated with mag matic ac tiv ity. In this area, they also sug gested the Early Cre ta ceous phase of ex ten sion and short en ing pe ri ods dur ing the Paleocene -Early Eocene, be fore the main Mid dle Eocene un con formity.…”