Lectostratotype of maikopian group – Belaya River section upstream of Maikop town (Western Ciscaucasia) in the Oligocene part

Abstract

Belaya River Section of Maikop deposits is the closest to the Maikop town, typical for Western and Central Ciscaucasus, well outcropped and studied and should be considered as a type section for the Maikop Group. Here it is possible to observe a continuous transition from the underlying light marls of Belaya Glina Formation to the dark clays of Pshekha Formation at the base of the Maikop succession. Pshekha Fm is characterized by nannoplankton NP21 and NP22 zones, dinocysts Phthanoperidinium amoenum (D13) and Wetzeliella symmetrica zones, mollusk association with Pterolucina batalpashinica at the bottom and rich fish fauna. The succession shows a normal polarity chron C13n for the base of the Pshekha and revers polarity C12r above.
 Marl of Polbian Bed with brackish Lower Solenovian mollusks, ostracod association with Disopontocipris oligocaenica, nannoplankton of NP23 Zone and dinocysts of Wetzeliella gohtii Zone lies above with erosion contact. Overlying Lower Morozkina Balka Subformation contains from non-calcareous clays and concludes the remains of fish and dinocysts of Wetzeliella gohtii Zone. The Upper Morozkina Balka Subformation contains calcareous sublayers with nannoplankton NP23 Zone in lower part and NP24 one above, dinocysts Chiropteridium partispinatum Zone, Rhombodinium draco Subzone. Polarity pattern we interpret to correspond to C10n, C9r and C9n.
 Batalpashinsk Formation corresponds to the time of maximum hydrogen sulfide contamination of the Late Oligocene basin and is dated by nannoplankton NP25 Zone, and dinocysts Chiropteridium patrispinatum Zone with Rhombodinium draco Subzone in lower part and Deflandrea spinulosa (non typica) Subzone in the middle and upper parts. Septarian+Zelenchuk Fm is composed of clays with septarian concretions, and interbedded sands with the same dinocysts and foraminifera with Spiroplectammina aff. terekensis. Calcareous interlayers in the top of the formation conclude nannoplankton of NP25-NN1 Zone. Karadzhalga Formation is composed mainly “fish lithofacies” and includes dinocysts zone Labyrinthodinium truncatum (Lower Miocene) in basal part.

Biostratigraphy and paleoenvironments of the Oligocene succession(İhsaniye Formation) at Karaburun (NW Turkey)

“…This same formation is carbonate-poor within offshore wells (Sachsenhofer et al, 2009). The Early Oligocene portion of the Maykop Suite at its type locality on the north side of the Greater Caucasus has been well documented (Popov et al, 1993;Akhmetiev et al, 1995;Zaporozhets, 1999;Saint-Germès et al, 2000;Zaporozhets and Akmetiev, 2017;Sachsenhofer et al, 2017;Popov et al, 2019). The relevant section is approximately 200-m thick, much thicker than at Karaburun, and consists of the Pshekha, Polba and Morozkina Balka formations.…”

“…This might be in part because of paleoenvironmental differences and differing taxonomic concepts. The Belaya River section is the type section for the Maykop Suite (Popov et al, 2019), where the succession is dominated by black shales reflecting bottom-water anoxia in basinal conditions that are episodically brackish (Sachsenhofer et al, 2017). As discussed in the section on paleoenvironments, the Karaburun section generally represents a mostly well- oxygenated outer shelf to slope succession.…”

“…Nonetheless, water depths might have been substantial. Based on the presence of fossil fish with photophores and the disappearance of aragonitic-shelled pteropods, Sachsenhofer et al (2017) and Popov et al (2019) estimate that water depths might have been as great as 1000 m, much greater than might be estimated at Karaburun. Unlike at Karaburun, deposition was more consistently anoxic.…”

“…In several parts of Paratethys, the onset of intra-Early Oligocene nannofossil Zone NP23 corresponds to a significant reduction in marine salinity (e.g., Budilová et al, 1992;Popov et al, 1993) as determined by distinctive blooms of dinocysts and acritarchs (Hystrichokolpoma, Batiascasphaera sphaerica, Horologinella), calcareous nannofossils (Reticulofenestra ornata, Transversopontis fibula, Transversopontis latus), ostracods (Disopontocipris oligocaenica) and molluscs (Janschinella, Lenticorbula). These assemblages occur in the type Maykop Suite section on the northern side of the Greater Caucasus (Popov et al, 1985;Voronina and Popov, 1984;Sachsenhofer et al, 2017;Popov et al, 2019) and the nannofossil assemblage ("Polbinian-type nannoflora") has been seen in the Caucasus and other parts of Central and Eastern Paratethys, even as far east as the north Ustyurt Plateau between the Caspian and Aral seas and as far west as the Bavarian Foreland Molasse (Nagymarosy and Voronina, 1993;Melinte-Dobrinescu and Brustur, 2008). This "Solenovian" event is said to be widespread throughout Paratethys (Popov et al, 2002;Popov and Stolyarov, 1996;Sachsenhofer et al, 2018) and has been detected in the Bulgarian Western Black Sea (Sachsenhofer et al, 2009Mayer et al, 2018) and in central Paratethys (Popov et al, 1993;Rusu, 1999;Schulz et al, 2004Schulz et al, , 2005Ozsvárt et al, 2016).…”

Stratigraphy, Sedimentology and Geochemistry of the Oligocene – Lower Miocene Maikop Group in Dagestan, Ne Caucasus

“…Other stratigraphic divisions of the Maikop Group were proposed during later studies of the Paleogene succession in the North Caucasus. However, these schemes were based on the study of Maikopian successions located at some distance to the west or north of Dagestan (Zhizhchenkо, 1953Grossgeim, 1960;Popov et al, 2019;Zastrozhnov et al, 2019). These stratigraphic schemes are not reviewed here because their correlation with the fossilpoor succession in Dagestan is still somewhat tenuous.…”