Structural and sedimentary evidence from the northern margin of the Tauride platform in south central Turkey used to test alternative models of Tethys during Early Mesozoic time

摘要

Critical to reconstruction of the Tethys ocean is the nature and significance of a reported latest Triassic "Cimmerian" tectonic event in the Tauride Mountains of south central Turkey. In one published model, a "Cimmerian" continental fragment, including the Tauride platform rifted from the northern margin of Gondwana and collided with a Eurasian-derived "Anatolide" continental fragment during Late Triassic time, causing orogenic deformation of the Tauride continental platform. In a second published model, southward subduction of a Palaeotethyan ocean opened a back-arc basin associated with rift-related uplift of the Tauride platform during Early Triassic time. The Tauride platform remained as a north-facing passive margin from the Mid-Late Triassic to Late Cretaceous without further deformation. In a third published model, a continental fragment rifted from a Tauride-Anatolide platform in the south, opening a small ocean basin (Ankara-Izmir ocean) to the north by Mid-Late Triassic time. Late Triassic deformation and uplift of the Tauride platform possibly resulted from far-field stress transmission from the Cimmerian orogeny that affected the Eurasian margin. in an additional model, a Tauride-Anatolide continent experienced a rift-related evolution, culminating in a pulse of extension-related uplift during the latest Triassic, followed by seafloor spreading to the north. The models are tested using evidence from relatively autochthonous Tauride units (Geyik Dag: Sultan Dag) and over-riding thrust sheets (Hadim (Aladag) nappe; Bolkar nappe). Geological mapping of critical areas and related structural evidence show that most of the deformation in the area can be related to Late Cretaceous and Early Cenozoic (Alpine) emplacement of the Tauride nappes, although Late Triassic compressional deformation is likely at one locality. Sedimentary evidence from the Cayir Formation, a widespread -latest Triassic-earliest Jurassic clastic sequence shows that it accumulated in a range of non-marine, to locally shallow-marine, fluvial, to deltaic settings. Palaeocurrent data indicate mainly southward sediment transport. Most of the material was derived from lithologies equivalent to those exposed within the underlying Tauride platform and within an Upper Palaeozoic "basement" unit (Konya Complex) to the north. A combination of the available structural, sedimentary and stratigraphical information from the Tauride region, and international comparisons lead us to exclude the presence of a Palaeotethyan suture of latest Triassic age within the Taurides. Rather we explain the Late Triassic-Early Jurassic Tauride geology mainly in terms of the uplift of a basement unit that was located along northern margin of the Tauride carbonate platform, associated with opening of the Izmir-Ankara ocean to the north. (C) 2008 Elsevier B,V. All rights reserved.