Skip to Main Content
Book Chapter

Stratigraphy, petrogenesis and geodynamic setting of Late Cretaceous volcanism on the SW margin of the Black Sea, Turkey

By
Mehmet Keskİn
Mehmet Keskİn
Department of Geological Engineering, Faculty of Engineering, İstanbul University, 34320 Avcılar, İstanbul, Turkey
Search for other works by this author on:
Okan Tüysüz
Okan Tüysüz
Eurasia Institute of Earth Sciences and Faculty of Mines, İstanbul Technical University, 34469 Maslak, İstanbul, Turkey
Search for other works by this author on:
Published:
January 01, 2018

Abstract

The Western Pontide Magmatic Belt consists of two different magmatic series corresponding to two distinct periods of intense volcanism, separated by a pelagic limestone marker horizon resting on a regional unconformity. The first stage of magmatism and associated extensional tectonic regime prevailed in the region between the Middle Turonian and Early Santonian. During the first stage, magmas were derived from a depleted mantle source containing a clear subduction signature. The extrusives intercalated with marine clastic sediments and pelagic carbonates associated with thick debris-flow horizons and olistoliths. Based on geochemistry and depositional features, the first stage is interpreted as an extensional ensialic arc setting developed in response to northwards subduction of the Tethys Ocean beneath the southern margin of Laurasia. During the Late Santonian, the volcanism stopped and the whole region suddenly subsided with the deposition of a thin, but laterally continuous, pelagic limestone horizon. This subsidence may imply the break-up of the Laurasian continental lithosphere and the beginning of oceanic spreading in the Western Black Sea Basin. The intensified extension is interpreted to be linked to the southwards rollback of the subducting slab.

During the second stage in the Campanian, magmas were derived from two contrasting mantle sources: (1) a depleted lithospheric mantle enriched by a subduction component; and (2) an enriched asthenospheric mantle which is similar to that of the ocean island basalts (OIB). The depleted lithospheric source may be linked to the subcontinental lithospheric mantle of Laurasia, which was metasomatized by the previous Tethyan subduction event rather than by an active arc magmatism. Lavas derived from the depleted source are abundant throughout the stratigraphic column, whereas those from the enriched source dominate the end of the second stage. The presence of the alkaline lavas may indicate thinning of the lithosphere and upwelling of the asthenospheric mantle in the matured stages of rifting. We argue that the main cause of both rifting and temporal change in magma generation was the steepening and rollback of the northwards subducting slab of the Tethys Ocean. The aforementioned rollback also caused the Istanbul Zone to be moved to the south, and colliding with the Sakarya Zone in the south during the Maastrichtian. Based on geochemical, stratigraphic, palaeontological and sedimentary data, we suggest that the oceanic Western Black Sea Basin opened as an intra-arc basin during Turonian–Santonian time.

Supplementary material: The full geochemical dataset in MS Excel workbook format is available at https://doi.org/10.6084/m9.figshare.c.3841255

You do not currently have access to this article.

Figures & Tables

Contents

Geological Society, London, Special Publications

Petroleum Geology of the Black Sea

M. D. Simmons
M. D. Simmons
Halliburton, UK
Search for other works by this author on:
G. C. Tari
G. C. Tari
OMV, Austria
Search for other works by this author on:
A. I. Okay
A. I. Okay
Eurasia Institute of Earth Sciences, Turkey
Search for other works by this author on:
Geological Society of London
Volume
464
ISBN electronic:
9781786203724
Publication date:
January 01, 2018

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal