Supradetachment basin evolution unraveled by detrital apatite fission track analysis - The example of the Gediz Graben (Menderes Massif, Western Turkey)
Résumé
The Menderes Massif of Western Turkey in an outstanding
example of Tertiary continental metamorphic core complex exhumed
during upper Oligocene – Miocene times; its exhumation
was accompanied by the development of a series of continental
E-W trending basins. Several studies addressed the exhumation
history of the massif, but the relative relevance of the identified exhumation
events and the depositional history of these basins is still
poorly defined. In this study, we focused our investigations on the
Gediz Graben supradetachment basin, which has been used as a
case history to illustrate the benefits of a comprehensive approach
to detrital apatite fission track dating that combines analysis of
modern river sediments, analysis of fossil sedimentary successions,
and mineral fertility determinations. This approach allowed us (i)
to constrain the maximum age for the beginning of sedimentation
in the basin, after providing that post depositional annealing was
negligible, (ii) to identify major exhumation events recorded in the
Neogene-to-Quaternary sedimentary fill of the basin, (iii) to reconstruct
the exhumation history of bedrock unit at the footwall and
at the hanging wall of the Gediz detachment, and (iv) to reconstruct
the modern short-term erosion pattern of the study area.
Three main exhumation events with different spatial relevance
have been identified in the area, related to the main exhumation
of the Menderes Massif, to a major structural reorganization in
the basin resulting in the exhumation of the margins of the Central
Menderes Massif, and to a localized event related to the final
exhumation of the Gediz detachment and its intrusive footwall.
Our results, integrated with field evidences, allowed us to propose
a coherent 4D reconstruction for the evolution of the Gediz
Graben. The implications of the proposed model for the Cenozoic
evolution of the Menderes Massif and for the Aegean extensional
region more in general are eventually discussed.