Supradetachment basin evolution unravelled by detritalapatite fission track analysis: the Gediz Graben (MenderesMassif,WesternTurkey)

摘要

The Menderes Massif is a Tertiarymetamorphic core complex tectonically exhumed in the late Oligocene-Miocene during coeval development of a series of E-W-trending basins. This study analyses the source-to-sink evolution of the Gediz Graben and the exhumation pattern of the Central MenderesMassif at the footwall and hanging wall of the Gediz Detachment Fault. We use a comprehensive approach to detrital apatite fission track dating combining analysis of modern river sediments, analysis of fossil sedimentary successions and mineral fertility determinations. This approach allowed us to: (i) define the modern short-term erosion pattern of the study area, (ii) unravel the long-term exhumation history, (iii) identify major exhumation events recorded in the sedimentary basin fill and (iv) constrain the maximum depositional age of the sedimentary succession. Three main exhumation events are recorded in the analysed detrital samples: (i) a late Oligocene/early Miocene exhumation event involving the whole Menderes Massif; (ii) a late Miocene event involving the northern edge of the Central MenderesMassif; (iii) a Plio-Quaternary more localized event involving only the western part of the southern margin of the basin (Salihli area) and bringing to the surface the Gediz Detachment and its intrusive footwall (Salihli granodiorite). The modern short-term erosion pattern closely reflects this latter Plio-Quaternary event. Single grain-age distributions in the sedimentary basin fill highlight drainage pattern reorganizations in correspondence of the transition between different stratigraphic units, and allowed to better constrain the depositional age of the sedimentary units of the basin pointing to a possible onset of sedimentation in the basin during the middle Miocene.