Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

Bruno Tomljenović,Kamil Ustaszewski,Philipp Balling,Wim Spakman,Christoph Grützner

doi:10.1038/s41598-021-81561-5

Bruno Tomljenović, Kamil Ustaszewski + Show 3 more

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https://doi.org/10.1038/s41598-021-81561-5

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Abstract

The Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

Highlights

The Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times
Crustal thickening, and foreland flexure in the External Dinarides led to the deposition of Eocene– Oligocene syntectonic deposits[27,28,29,30,31], subdivided into the proximal coarse-grained molasse (Promina Beds)[27,28,29,30] and the fine-grained distal “flysch” d eposits[31]
The lack of suitable marker beds younger than the Miocene Dinaric Lake Sediments make it difficult to quantify the exact amount of Neogene shortening in the Dinarides, several studies show a substantial amount of post-uplift Neogene s hortening[17,46,47]

Summary

Introduction

The Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Delamination is the process that decouples negatively-buoyant lithospheric mantle from buoyant crust, allowing replacement with less dense asthenosphere and leading to surface and Moho uplift and cogenetic m agmatism[8] This can be either achieved by syn-collisional[9] or by post-collisional delamination[8]. In this study we identify large, flat surfaces on Paleogene proximal syn-tectonic marine deposits and on older Mesozoic Adriatic carbonate platform bedrock along the Dinaric coast (Fig. 1). Such surfaces are absent within Miocene lacustrine sediments that were deposited around 18–13 Ma in a system of intramontane Dinaric lakes

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