Last week we focused on the urban site (see July 27-August 2), but this week our activities--directed by Philippe Muchez (KULeuven), assisted by Dominique Similox-Tohon and Griet Verhaert (both geology doctoral students at KULeuven)--were carried out on a much larger topographical scale within the city's ancient territory. Archaeological evidence shows that Sagalassos has been struck by a number of serious earthquakes, the last one registered in the archaeological record occurred in the mid-seventh century. Our data show that the city was most probably situated in the epicenter of this earthquake and that the causative fault should be located within the city's territory. This year, we're investigating possible active faults identified by satellite imagery in combination with the analysis of the Digital Elevation Model and by our survey in 2002. We examined faults on the Aglasun Daglari and in the area of Sarikaya extensively for the characteristics of active faults, sampling fault breccias and calcite precipitates. Normal faults in the Aegean region are often characterized by a sequence of different types of breccia. The calcite precipitates are geochemically analyzed to constrain the nature and origin of the fluids associated with the faulting events and their timing.
Study of the precipitates contributes to the dating of seismic events and the understanding of fault kinematics. We are checking the applicability and methodology of a new study method, using carbonate precipitates to reconstruct neotectonic activity. Besides measuring orientation data, we have sampled fault-related calcites and the different zone-parallel layers of fault breccia. A mineralogical, geochemical and microthermometric study of the carbonates will allow us to deduce the nature of the fluids responsible for precipitation. Hence we can distinguish fluids that circulated through joints and faults at shallow depth from deep "exotic" fluids that were expelled during fault activity. If possible, we will date calcites reflecting important tectonic activity by means of U-Th and/or U-Pb dating techniques in order to determine a geochronological evolution of the changing stress fields and the absolute timing of important fault activities. For the different fault breccia, we'll do a fabric analysis on a mesoscopic and microscopic scale to fully characterise them and to determine their relation with fault activity. We've already made a detailed geological map of the area around Sarikaya to allow the identification and characterization of the multiple faults present in this small but complex area and to determine their period of activity.
The fault zones at the Aglasun Daglari and Sarikaya are all composed of multiple-slip planes and zone-parallel layers of fault breccia, which indicate several faulting events. The characterization of the fault planes will allow identification of other fault-plane surfaces now less visible through intense weathering. This study stresses the sensitivity of the area for geologically recent earthquakes, but we'll also correlate the tectonic activity with the larger plate tectonic setting of Southwest Turkey and existing stress fields.