Measuring lithospheric stretching on Tethyan passive margins

Abstract

Preliminary estimates of lithospheric stretching have been made by examining 63 stratigraphic sections, from the northern and southern Tethyan margins (southeast France to Bulgaria). The study was centred on the Italian Southern Alps (the Dolomites), a portion of the southern margin within the external zones of the Alpine orogen. Sections were decompacted and backstripped using the standard procedure, allowing for errors in palaeowater-depth estimates. Theoretical subsidence curves based on the finite-duration stretching model were then fitted to the resultant water-loaded subsidence curves in an attempt to clarify the pre-compressional tectonic history of the region. According to our results, stretching started in the early to mid-Triassic and lasted 30–40 Ma. This conclusion is broadly in agreement with some previously published estimates. The stretching factor, β, is generally small (1.1–1.3), especially in southeast France and northern Italy. Larger values of β occur in the Balkans ( c. 1.5). To our knowledge, the finite-duration stretching model has not yet been applied to water-loaded stratigraphic sections from the Tethyan belt. Theory and observation appear to agree well.