Integrated stratigraphy of the Eocene-Oligocene deposits of the northern Caucasus (Belaya River, Russia): Intermittent oxygen-depleted episodes in the Peri-Tethys and Paratethys

A. van der Boon*, R. van der Ploeg, M. J. Cramwinckel, K. F. Kuiper, S. V. Popov, I. P. Tabachnikova, D. V. Palcu, W. Krijgsman

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The sedimentary succession along the Belaya River (North Caucasus) provides a record of middle Eocene to Miocene sediments. This time interval is well known for its important climatic transitions (e.g., Middle Eocene Climate Optimum (MECO) and Eocene-Oligocene Transition (EOT)), and changes in basin configuration from Peri-Tethys to Paratethys. The Belaya section contains two intervals marked by oxygen-depleted sediments; the Eocene Kuma Formation of the Peri-Tethys and the Oligocene Maikop Group of the Paratethys. Both are considered important source rocks for hydrocarbon exploration in the Black Sea and Caspian Sea. We present integrated stratigraphic results of the Belaya River section using calcareous nannoplankton biostratigraphy, magnetostratigraphy and 40Ar/39Ar dating. Furthermore, we investigate the geochemical character of the sediments using X-ray fluorescence (XRF) and stable carbon and oxygen isotopes. A middle Eocene age for the lower part of the succession is established from nannoplankton biostratigraphy. The Kuma Formation is dated between 42.1 and 38.4 Ma based on the assumption of constant sediment accumulation rates. A negative oxygen isotope excursion in the middle part of the Kuma Formation could be related to the MECO (~40 Ma). The onset of the Maikop Group is dated around the base of chron C13n at an age of ~33.7 Ma, close to the Eocene-Oligocene boundary. Based on geochemical results, we show that the Kuma Formation and Maikop Group correspond to two different episodes of intensified oceanic oxygen depletion in the succession. We hypothesise that oxygen-depletion as recorded in the Kuma Formation is linked to an increased nutrient input in the open marine Peri-Tethys due to widespread volcanism in the Neotethys subduction zone, while oxygen-depletion as recorded in the Maikop Group is linked to basin restriction caused by the eustatic sea-level fall straddling the Eocene – Oligocene boundary triggering stratified conditions in the semi-isolated Paratethys Sea.

Original languageEnglish
Article number109395
Pages (from-to)1-16
Number of pages16
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume536
Early online date16 Oct 2019
DOIs
Publication statusPublished - 15 Dec 2019

Keywords

  • Anoxia
  • Eocene-Oligocene Transition
  • Kuma Formation
  • Maikop
  • MECO
  • Middle Eocene Climatic Optimum

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