CENOZOIC COOLING HISTORIES IN THE MENDERES MASSIF, WESTERN TURKEY, MAY BE CAUSED BY EROSION AND FLAT SUBDUCTION, NOT LOW-ANGLE NORMAL FAULTING

Abstract

Since the early 1990s, a prolific literature has developed on the interpretation within western Turkey of apparent Mid to Late Cenozoic low-angle normal faults. Extension on these structures has been thought responsible for the exhumation of this region's principal metamorphic massif, the Menderes Massif, which has thus been interpreted as a metamorphic core complex. Nonetheless, no convincing supporting structural evidence has emerged: some reported instances of low-angle normal faulting affecting the Menderes Massif can be shown from field relationships to have formed as steep normal faults and to have since become back-tilted; others seem to be misinterpretations of structures with no demonstrable relationship to extension at all. The main evidence for low-angle normal faulting in this region has instead emerged through thermochronology, which indicates highly non-uniform cooling histories that have seemed to lack any other explanation. However, this evidence can alternatively be explained by a combination of the cooling effects caused by flat subduction and by erosion. There is thus no evidence for Cenozoic low-angle normal faulting affecting the Menderes Massif. Extension started at ∼11 Ma in parts of western Turkey; but most of this region's Late Cenozoic extension—on normal faults with steep initial dips—has occurred since ∼7 Ma, synchronous with slip on the North Anatolian Fault Zone.