Onset of Maikop sedimentation and cessation of Eocene arc volcanism in the Talysh Mountains, Azerbaijan

Abstract

The Maikop Series forms an important source rock in the former Paratethys. Deposition is often interpreted as anoxic, linked to restriction of the Paratethys. The Pirembel formation in the Talysh Mountains (Azerbaijan) is attributed to the Maikop Series and was deposited above the Eocene volcanic Peshtasar formation. Dating the onset of anoxia could help to distinguish glacio-eustatic from tectonic causes of restriction. We integrated magnetostratigraphy and biostratigraphy to date the onset of Pirembel sedimentation and used geochemistry to characterize the tectonic setting of the Peshtasar volcanic rocks. The onset of Maikop sedimentation in the Talysh was determined to be 37.7 Ma, ruling out a link with the major sea-level drop at the Eocene–Oligocene Transition (33.9 Ma) and favouring a tectonic cause. Extrapolating the average sedimentation rate (34 cm kyr) suggests that the entire Pirembel formation belongs to the Late Eocene. We hypothesize that the end of volcanism is important in the transition to Pirembel sedimentation. The palaeomagnetic and geochemistry results for the volcanic rocks cluster in three groups, suggesting three distinct episodes of volcanism. Volcanic sills within the Eocene Arkevan formation plot exactly on these groups, confirming the relationship between the Arkevan and Peshtasar formations. Volcanic rocks of the Talysh show continental-arc signatures and may be related to an Eocene volcanic belt extending towards southeastern Iran. Supplementary material: The full analytical data of the Ar–Ar dating are available at http://www.geolsoc.org.uk/SUP18851