Subsurface structural geology of the eastern part of the Büyük Menderes Graben, western Turkey: implications for structural evolution of the Büyük Menderes and Alasehir Grabens
The Central Menderes Metamorphic Core complex of Western Anatolia, Turkey is bordered by two major approximately E-W trending seismically active grabens: the Alasehir and Büyük Menderes Grabens (BMG). Seven depth-converted 2-D seismic reflection profiles and well log data from one well are used to delineate the geometry of the subsurface structural features and the Cenozoic stratigraphy of the eastern part of the BMG. Depth converted seismic profiles indicate ~2100 meters (m) thickness of Early Miocene to recent sedimentary rock units in the BMG. The south-dipping Graben Bounding Fault (GBF) along the northern margin of the BMG has been active probably since Miocene sedimentation in the basin. Miocene to Pliocene (Neogene) sedimentary units show thickness variations along the three N-S cross-sections constructed based on the structural interpretation of the seismic data. The Neogene units are thickest in the center of the graben, and illustrate a wedge-shaped geometry towards the north and south-dipping graben bounding faults flanking the graben. Due to this geometry, syn-sedimentary extension in the graben has not formed a rollover structure and associate extensional folds and faults. The subsurface structural geometry of the BMG contrasts with the structural geometry of the Neogene sedimentary units in the Alasehir Graben (AG). The AG contains a thicker (3000 m) Neogene sedimentary succession (Çiftçi and Bozkurt, 2009, 2010), a rollover structure and a supradetachment basin were interpreted by (Çemen et al., 2006; Çiftçi and Bozkurt, 2009, 2010). Although the AG and BMG may have started to form simultaneously in Early Miocene time during the Cenozoic extensional phase in the region, they do not contain symmetrical structural features.