Differential tectonics of Aydın Range in western Anatolia Extensional Province: Inferences from catchment-wide erosion, river incision, and range-front deposition

Abstract

The western Anatolian Extensional Province is a rapidly extending region characterized by dynamic landscapes resulting from the ongoing deformation of the Earth's crust. The Aydın Range, located along the northern margin of the Büyük Menderes Graben, is a major horst within the western Anatolian Extensional Province. This region has experienced a series of extensional events since the Late Oligocene, leading to ongoing uplift and erosion, shaping a complex landscape of mountains, valleys, and river systems. The tectonic deformation within the Aydın Range has not been uniform, resulting in differential uplift along the range and variations in erosion rates. This differential uplift has shaped the landscape, giving rise to distinctive erosional and depositional landforms along the northern margin of the Büyük Menderes Graben. The morphostratigraphy and morphology of these landforms provide valuable insights into the source-to-sink relationships and the Quaternary tectonics of the region. The active tectonic regime and steep topography of the Aydın Range create favorable conditions for enhanced erosion rates, leading to the development of the distinctive range-front deposition. However, the understanding of the active tectonics of the Aydın Range and its relationship to catchment erosion, river incision, and range-front deposition remains limited. To understand the differential tectonic uplift pattern of the Aydın Range, this thesis focuses on erosional and depositional features along the southern flank of the Aydın Range. The main objective of this Ph.D. thesis is to unravel the interplay between differential rock uplift dynamics of the Aydın Range and the range-front depositional and erosional patterns within the range, considering the tectonic activity, lithology, and varying erosion rates across the region. The study area offers favorable conditions for analysis, including numerous alluvial fans aligned along a segmented normal fault, similar climatic and vegetative characteristics within catchments, and a mixture of granite and gneiss lithologies. A comprehensive approach combining catchment-wide erosion analysis, river incision analysis, river longitudinal profile analysis, and range-front deposition analysis is employed. Catchment-wide erosion patterns, based on 10Be cosmogenic nuclides are examined to understand the relative contributions of various factors on erosional dynamics and decipher the tectonic uplift pattern of the range. River incision processes and channel characteristics are investigated to gain insights into underlying tectonic processes and their spatial variations. Furthermore, the morphology of alluvial fans at the range front are studied to evaluate tectonic uplift and the relative contributions of different processes to sedimentation patterns. Higher catchment-wide erosion rates and higher river incision rates in Section 3 and Section 5 of the Aydın Range are shown by the results. In addition, higher channel steepness index values and slope break knickpoint distributions imply that a higher rock uplift rate is responsible for thicker alluvial fans in sections 3 and 5. In contrast, Section 1, section 2, and Section 4 have lower catchment-wide erosion rates and lower river incision rates. In addition, the lower ksn and absence of slope break knickpoints in these sections is an indication that these sections have lower tectonic rock uplift. This resulted in the less thick and spatially larger distribution of alluvial fans in Section 1, section 2, and Section 5. A comprehensive understanding of the differential tectonics and range-front deposition processes is provided by the source-to-sink approach employed in this thesis, enhancing knowledge of the active tectonics and surface processes in the region. Additionally, the detailed morphostratigraphy of Quaternary landforms in the study area provides valuable insights into landscape evolution and hazard assessment in this dynamic setting. The map of Quaternary landforms fills the existing gaps in the region-wide correlations and maps associated with the Quaternary geology and geomorphology, facilitating a more comprehensive understanding of the tectonic processes shaping the Aydın Range.