Abstract
The Tethys Ocean was compartmentalized into the Mediterranean Sea and Indian Ocean during the early Miocene, yet the exact nature and timing of this disconnection are not well understood. Here we present two new neodymium isotope records from isolated carbonate platforms on both sides of the closing seaway, Malta (outcrop sampling) and the Maldives (IODP Site U1468), to constrain the evolution of past water mass exchange between the present day Mediterranean Sea and Indian Ocean via the Mesopotamian Seaway. Combining these data with box modeling results indicates that water mass exchange was reduced by ~90% in a first step at ca. 20 Ma. The terminal closure of the seaway then coincided with the sea level drop caused by the onset of permanent glaciation of Antarctica at ca. 13.8 Ma. The termination of meridional water mass exchange through the Tethyan Seaway resulted in a global reorganization of currents, paved the way to the development of upwelling in the Arabian Sea and possibly led to a strengthening of South Asian Monsoon.
Highlights
Northward movement of the African, Australian and Indian plates, which started during the Late Cretaceous and persisted until the Oligocene, resulted in a continuous narrowing of the vast Tethys basin and eventually led to the formation of the enclosed, marginal Mediterranean and Black Seas
We present a paleoceanographic approach which allows the reconstruction of water mass exchange between the Indian Ocean and the Mediterranean across the Tethyan Seaway based on radiogenic Nd isotopes
Similar studies have been used to infer that the final closure of deep water mass exchange across the Central American Seaway was established ca. 5 Ma16 and that subsequent Nd isotope shifts in the Atlantic Ocean were a consequence of linked changes in Atlantic circulation and continental weathering inputs[17,18,19]
Summary
Northward movement of the African, Australian and Indian plates, which started during the Late Cretaceous (ca. 80 Ma) and persisted until the Oligocene, resulted in a continuous narrowing of the vast Tethys basin and eventually led to the formation of the enclosed, marginal Mediterranean and Black Seas. The goal of this study was to refine previous estimations based on two new Nd isotope datasets from isolated carbonate platforms far from adjacent volcanic or immediate terrestrial contributions in both the Mediterranean Sea (Malta) and in the western Indian Ocean (Maldives) Combining these results with a simple box modelling approach to calculate seawater Nd isotope values as a function of through-flow strength across the East Tethyan/ Mesopotamian gateway allows to (i) globally correlate stratigraphic constraints on the changes in connectivity and (ii) to estimate the magnitude of change in the volume flow of water across the seaway. The connection was terminated following the Langhian-Serravallian transition, which coincided with the onset of permanent glaciation of Antarctica[24]
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