STRATIGRAPHY OF THE UPPER CRETACEOUS SEDIMENTS WITH OCEANIC RED BEDS (CORBs), UKRAINIAN CARPATHIANS
Authors: Hnylko S.R. , Hnylko O.M. , Suprun I.S. , Navarivska K.O. , Heneralova L.V. 
Published: October 2023

Cretaceous deposits containing pelagic red beds (CORBs – Cretaceous Oceanic Red Beds) are developed in the Ukrainian Carpathians. CORBs have a global distribution, they are sharply depleted in organic matter and their formation is associated with periods of cooling and intensive circulation of cold, oxygen-enriched deep-sea currents that oxidize organic carbon. CORBs in the Ukrainian Carpathians are common in the Upper Cretaceous, while the Lower Cretaceous sediments, especially in the Outer (Flysch) Carpathians, are often enriched in organic matter (in particular the black shales of the Shypot and Spas formations). Such change in sediments enriched and depleted in organic matter may be associated with regular climate changes.
In the Inner Carpathians, in the both the Peniny Klippen Belt and the Marmarosh Klippen Zone, CORBs are represented by thick (100-200 m) mostly red-colored marls and shales that make up the Turonian – Maastrichtian Puchov Formation. A fragment of the Puchov Formation of the Turonian age is presented in the Marmarosh Massif. Stratigraphically, the lowest CORBs represented by layers of pink marls are noted in the upper part (Middle-Upper Cenomanian) of the Tysalo Formation in the Peniny Klippen Belt. Deposits containing CORBs in the Peniny Klippen Belt are intensively deformed, in some places they are transformed into thin shale rocks or friction mud and are part of the tectonic mélange, while in the Marmarosh Klippen Zone they lie monoclinally and are weakly deformed.
In the Outer Carpathians, CORBs are represented by: Turonian–Paleocene variegated shales and marls of the Holyatyn Beds (Subsilesian Nappe); Turonian–Coniacian red-colored and variegated shales belonging to the lower member of the Yalovets Formation (Dukla, Chornohora, Svydovets, and Krasnoshora nappes); and pack of Turonian variegated marls included in the Sukhiv Formation (Burkut nappe). CORBs represented by red-brown interlayers, occur both in the uppermust Albian– lower Cenomanian (Eiffellithus turriseiffeli Zone) of the Sukhiv Formation, and in the Santonian upper member of the Yalovets Formation. CORBs in the Outer Carpathians are deformed to a greater or lesser extent, plastic marls of the Sukhiv Formation are especially strongly deformed, which makes it much more difficult to establish their stratigraphic sequence.
The age of the deposits of the Ukrainian Carpathians, which contain CORBs, has been clarified. The studied sediments are correlated with the Geologic Time Scale (2020) on the basis of nannoplankton and planktonic foraminifera.
The biozonal scale based on nannoplankton of A.M. Romaniv is compared in the range BC27/UC0 (upper Albian – lower Cenomanian) – UC20 (upper Maastrichtian) according to the first appearance of zonal species according to the scale of J. Barnett (1998). Accordantly, the Eiffellithus turriseiffeli Zone (uppermost Albian–Lower Senomanian); Gartnerago obliquum Zone (Middle Senomanian–lowermost Turonian); Eiffellithus eximius-Marthasterites furcatus Zone (Lower Turonian–lowermost Upper Coniacian); Micula staurophora-Tetralithus obscurus-Broinsonia parca Zone (Upper Coniacian- lowermost Middle Campanian); Tetralithus aculeus Zone (Middle Campanian); Tetralithus? trifidus (Middle Campanian– lowermost Upper Campanian); Nephrolithus frequens (Upper Campanian–Upper Maastrichtian) are distinguished.
The biozonal division of the Upper Cretaceous of the Carpathians according to planktonic foraminifera after N.I. Maslakova was modified and compared with the biochronozones of a typical section of the Tethys region (Coccioni, Premoli Silva, 2015). In the studied sediments, the following zones are distinguished: Thalmanninella reicheli (middle part of the Lower Cenomanian), Rotalipora cushmani (middle part of the Lower Cenomanian–Upper Cenomanian), Helvetoglobotruncana helvetica (lower part of Turonian), Dicarinella concavata (top of Turonian–lowermost Santonian), Contusotruncana fornicata (most of Santonian), Globotruncanita elevata (lower part of the Campanian), Contusotruncana morozovae (middle part of the Campanian), Globotruncanita stuarti (top of the Campanian–lower part of the Maastrichtian), Abathomphalus mayaroensis (upper part of the Maastrichtian); beds with Thalmanninella globotruncanoides (lower part of the Lower Cenomanian), assemblage with Marginotruncana schneegansi, Marginotruncana sigali, Marginotruncana renzi (upper part of Turonian).
Benthic foraminifera Uvigerinammina jankoi Zone (Turonian); Spiroplectinella costata Zone (Coniacian–Lower Santonian); Caudammina gigantea Zone (Upper Santonian–Lower Campanian); Rzehakina inclusa Zone (Upper Campanian– Maastrichtian); Rzehakina fissistomata Zone (Paleocene) were identified accordantly to zonal schemes of L.D. Ponomaryova and B. Olszewska.
The lower boundary of the CORBs in the Ukrainian Carpathians is correlated with the Senomanian-Turonian boundary on the basis of appearance of planktonic foraminifers of Helvetoglobotruncana helvetica Zone and benthic foraminifers of Uvigerinammina jankoi Zone in the base of both Puchov Formation (Pieniny Klippen Belt) and Holyatun Beds (Subsilesian Nappe), as well as in the lowermost part of the Yalovets Formation (Dukla, Chornohora, Svydovets and Krasnoshora nappes).