Evidence for and significance of the Late Cretaceous Asteroussia event in the Gondwanan Ios basement terranes
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Published:2021-10-11
Issue:10
Volume:12
Page:2255-2275
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ISSN:1869-9529
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Container-title:Solid Earth
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language:en
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Short-container-title:Solid Earth
Author:
Yeung SoniaORCID, Forster MarnieORCID, Skourtsos EmmanuelORCID, Lister GordonORCID
Abstract
Abstract. The Late Cretaceous Asteroussia event as recorded in the Cyclades is a
potential key to the tectonic evolution of Western Tethys. Microstructural
analysis and 40Ar/39Ar geochronology on garnet–mica schists and
the underlying granitoid basement terrane on the island of Ios demonstrates
evidence of a Late Cretaceous high-pressure, medium-temperature (HP–MT)
metamorphic event. This suggests that the Asteroussia crystalline nappe on
Crete extended northward to include these Gondwanan tectonic slices. In this
case, the northern part of the Asteroussia nappe (on Ios) is overlain by the
terrane stack defined by the individual slices of the Cycladic
Eclogite–Blueschist Unit, whereas in the south (in Crete) the Asteroussia
slices are near the top of a nappe stack defined by the individual tectonic
units of the external Hellenides. This geometry implies that accretion of the
Ios basement terrane involved a significant leap of the subduction megathrust
(250–300 km) southward. Accretion needs to have commenced at or
about ∼38 Ma, when the already partially exhumed slices of the
Cycladic Eclogite–Blueschist Unit began to thrust over the Ios basement. By
∼35–34 Ma, the subduction jump had been accomplished, and
renewed rollback began the extreme extension that led to the exhumation of the
Ios metamorphic core complex.
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Earth-Surface Processes,Geochemistry and Petrology,Geology,Geophysics,Soil Science
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