Alper Gürbüz

Geometric characteristics of pull-apart basins

Pull-apart basins are depressions bounded on their sides by two or more strike-slip faults and on their ends by diagonal transfer faults. As proposed by theoretical, experimental, and numerical studies in the literature, there are angular and scale relationships between these faults. Here, I compiled the major results on geometries of pull-apart basins of previous workers and then examined the geometric characteristics of pull-apart basins along the North Anatolian fault zone for a comparison of current data in two and three dimensions. According to the results of my compilation from the literature and measurements of pull-apart examples from northern Turkey, the acute angles of this type of strike-slip basin are clustered at 30°–35°. In metric scale, the consistency in their two-dimensional (2-D) geometry is well known as an aspect ratio of 3:1 between length and width. Basin length is a function of stretching associated with strike-slip displacement, and increased displacement causes the width of the fault zone to increase, resulting in wider pull-apart basins. However, the depth of a pull-apart basin is a function of stretching associated with strike-slip displacement. In this study, comparison of data related to pull-apart basin scales from the literature suggests that the depth is related to the length and width.

Plio-Quaternary development of the Baklan–Dinar graben: implications for cross-graben formation in SW Turkey

Western Turkey is characterized mainly by E–W, NW–SE, and NE–SW-trending grabens. The reverse V-shaped geometry of the Baklan–Dinar graben is formed by coupling of the NE–SW-trending Baklan and the NW–SE-trending Dinar grabens, and is critical to an understanding of the structural evolution of the Aegean region. Its geometry indicates biaxial extension in the region, as proposed in the current literature (e.g. Temiz et al. 1997; Cihan et al. 2003). The Acıgöl and Burdur grabens parallel the axis of the Baklan graben in the south, and these three basins terminate against the Dinar fault. The Baklan Basin is bounded along both margins by the Baklan and Çal left-lateral oblique faults. Basin-fill deposits of the Baklan Basin thicken towards the Dinar fault, and the basin floor dips northeastward. In addition, geomorphological characteristics of the Baklan–Dinar graben indicate that the Dinar fault is relatively more active than the faults of the Baklan Basin. All available morphologic, structural, borehole, and geophysical data from the Baklan–Dinar graben define a cross-graben structure that developed during Plio-Quaternary uniaxial NE-directed extension in SW Turkey. In this framework, the Dinar fault plays the role of a breakaway fault of this formation. The increase in the normal components of the northwestern left-lateral oblique basin-bounding faults of the Baklan Basin is explained by the gradual steepening of the pitch of the slip vectors towards the northeast, because of capturing of the extension by the Dinar breakaway fault.

Complex basin evolution in the Gökova Gulf region: implications on the Late Cenozoic tectonics of southwest Turkey

Southwestern Turkey experienced a transition from crustal shortening to extension during Late Cenozoic, and evidence of this was recorded in four distinct basin types in the Muğla–Gökova Gulf region. During the Oligocene–Early Miocene, the upper slices of the southerly moving Lycian Nappes turned into north-dipping normal faults due to the acceleration of gravity. The Kale–Tavas Basin developed as a piggyback basin along the fault plane on hanging wall blocks of these normal faults. During Middle Miocene, a shift had occurred from local extension to N–S compression/transpression, during which sediments in the Eskihisar–Tınaz Basins were deposited in pull-apart regions of the Menderes Massif cover units, where nappe slices were already eroded. During the Late Miocene–Pliocene, a hiatus occurred from previous compressional/transpressional tectonism along intermountain basins and Yatağan Basin fills were deposited on Menderes Massif, Lycian Nappes, and on top of Oligo–Miocene sediments. Plio-Quaternary marked the activation of N–S extension and the development of the E–W-trending Muğla–Gökova Grabens, co-genetic equivalents of which are common throughout western Anatolia. Thus, the tectonic evolution of the western Anotolia during late Cenozoic was shifting from compressional to extensional with a relaxation period, suggesting a non-uniform evolution.

Genetic framework of Neogene–Quaternary basin closure process in central Turkey

Central Turkey represents the only orogenic plateau in the Mediterranean region. Also, the largest closed drainage basin and the largest intracontinental basin of Turkey, the Lake Tuz Basin, is located in this region. Results from a three-dimensional (3-D) computer modeling study of the Lake Tuz Basin indicate a southward-deepening freshwater lake basin with great depth in the Mio–Pliocene, which regressed toward the north during the Plio–Quaternary into the shallow saline lake basin it is today. The spatio-temporal variations of Neogene and Quaternary deposits reflect the main effects of internal forces (isostasy>volcanism>faulting) that were caused by lithospheric slab breakoff and subsequent asthenospheric upwelling under central Turkey. Climatic change played a relatively minor role during these periods and was closely associated with the results of internal forces.

Orientations of palaeotectonic features as a key to understanding the neotectonic block rotation of the Kocaeli peninsula, NW Turkey

Due to northward subduction of Neotethys, the İstanbul zone collided with the Sakarya zone in northwest Turkey during the early Eocene. Subsequently, this region was subjected to compressional forces during the late Eocene–early Miocene period. Folds, thrusts and reverse faults developed approximately parallel to long axes of the İstanbul zone. NNW–SSE oriented conjugate strike‐slip faults developed with continued contraction. In addition to the orientations of palaeotectonic features, the morphotectonic, stratigraphic and seismic characteristics expose differences between the northeastern Marmara peneplain and the southern Black Sea highland. This study reports causes of this diversity reflecting the neotectonic evolution of the İstanbul zone. The diversity is related to the clockwise rotation of the Kocaeli peninsula between two dextral zone‐bounding faults and two sinistral block‐bounding faults. The principle factors of this process were the development of the North Anatolian fault zone (NAFZ) and the related evolution of the Adapazarı–Karasu fault zone (AKFZ), the Bosphorus fault zone (BFZ) and the Northern Boundary fault (NBF).