Z. Mümtaz Hisarli

Curie Point Depth variations to infer thermal structure of the crust at the African-Eurasian convergence zone, SW Turkey

We examined the thermal structure of the crust across complex deformation zones in SW Turkey using the Curie Point Depth (CPD) estimates and made comparisons of the thermal state of the crust with the seismic activity to provide insights for spatial limits of brittle failure in this region. The CPD estimates of SW Turkey from 80 overlapping blocks vary from 9 to 20 km. SW Turkey has two regions of shallow CPD. The shallow CPD region in the Uşak-Afyon zone in western part of the study area is caused by upper crustal thinning and shallowing of high conductivity lower crust. The other shallow CPD region is in the Central Anatolian Volcanic Province in the eastern part of the study area and is thought to be related to the presence of silicate melts in the shallow-level crust. A NNW-SSE trending belt of deep CPD region separates these two zones and is located along the boundary of high (west) and low (east) seismic activities. It is interpreted that the regional thermal structure in SW Turkey is mainly controlled by the processes associated with the African-Eurasian plate convergence zone. The N-S lithospheric extension above the subducting slab created a thermal dome in Western Anatolia in response to upwelling of asthenosphere. Post-collisional magmatism of Neogene-Quaternary age generated another thermal dome in the eastern area. Comparison of the CPD variations with the seismic activity has shown that large earthquakes occur near the margins of the inferred regional thermal domes. Low seismic activity within the regionally active seismic areas seems to be associated with shallow CPD and high heat flow.

Comments on the Gravity and Magnetic Anomalies of Saros Bay using Wavelet Approach

In this paper, residual and regional gravity and magnetic anomalies of Saros Bay are separated using wavelet method. Wavelet is one of the modern, stochastic image approaches processing technique in electronics. The vertical, horizontal and diagonal components of wavelet output are evaluated simultaneously and an underground model is obtained by suitable cross-sections. Thus the geological and tectonic properties of Saros Bay are extracted. Our proposed model is confirmed by deep and shallow seismic researches of Turkish Petroleum Cooperation (TPAO). The South-East region of Saros Graben is formed by strike slip Ganos Fault and Anafartalar reverse Fault that lies on the east of Ganos Fault. On the Northwest region, there is strike slip component fault resulting in the Enez Graben. Here we detected two new oval type geological structure, both of them starting from the Eastern direction of Canakkale Dardanelles and but one of them continuing through Gelibolu Peninsuls, while the other tending to the Enez Graben. We think that these structures are the ruins of a very old sea in this region.

The Tectonic History of the Niğde-Kırşehir Massif and the Taurides since the Late Mesozoic: Paleomagnetic Evidence for Two-Phase Orogenic Curvature in Central Anatolia†

The Nigde-Kirsehir Massif, known also as the Central Anatolian Block, is bordered by the sutures of the NeoTethys Ocean. The Massif suffered several deformation phases during and after the consumption of the surrounding oceans and the post-collisional events of the continental pieces of Anatolia in latest Cretaceous to Miocene. Previous paleomagnetic studies on the Nigde-Kirsehir Massif and its surroundings displayed either insufficient data or have claimed large rotations and/or remagnetization. In order to understand the tectonic history of the Nigde-Kirsehir Massif and its adjacent blocks we have sampled 147 different sites in the age range of Upper Jurassic to Miocene from the Nigde-Kirsehir Massif throughout its W/SW and E/SE boundaries and the Central- Southeastern Taurides. The results display that except the limestones in Central Taurides, all rocks examined carry a primary magnetization. Among these an important finding is that rotations between the Massif and the Central-Eastern Taurides indicate an oroclinal bending with counterclockwise rotation of R=41.1°±7.6° in the SE and clockwise rotation of R=45.9°±9.3° in the Central Taurides from Upper Cretaceous rocks with respect to the African reference direction. Paleomagnetic rotations in the SE Taurides are compatible with the vergent direction of the thrusts generated from consumption of the Intra-Tauride ocean prior to post collisional convergence between Taurides and the Massif. In the Central Taurides it has been shown that the clockwise rotation of 45.9±9.3 started in Middle Eocene, because of a remagnetization in Upper Creataceous limestones. The deformation was linked to the final closure of the southern Neotethys and the collision between the African and Eurasian plates. In the Nigde-Kirsehir Massif counterclockwise rotation up to 25.5°±7.3° is recognised during Middle Eocene and interpreted in terms of block rotation together with the Taurides. After the Miocene a counterclockwise rotation of 16.8°±3.9° along the Eastern Taurides shows that this area was mostly affected by the westward movement of Anatolia despite the Nigde-Kirsehir Massif and its SW/W area-the Central Taurides, which is recognised as stable with counterclockwise rotation less than 10°.

Investigation into regional thermal structure of the Thrace Region, NW Turkey, from aeromagnetic and borehole data

The aeromagnetic values over the study region are relatively uniform except for a few anomalies in the northeastern and southwestern areas. Analyses of aeromagnetic data were performed in NW Turkey, in order to have a look into the subsurface regional thermal structure of the region. For this purpose, power spectra, reduced to pole (RTP), and band-pass filtered anomalies were produced using geophysical techniques. Band-pass filtered data were produced from the RTP aeromagnetic anomalies to isolate near surface and undesired deep effects. Based on the aeromagnetic data interpretation, the thickness of the magnetized crust, named the Curie Point Depth (CPD), in the study area lies between 9.7 and 20.3 km. The CPD estimates in the Thrace region of Turkey indicate two shallow CPD (SCPD1 and SCPD2) zones (the Istranca Massif and the Saros Graben area). The deep CPD are located within the Thrace Basin with sediment thickness of about 9 km. The corresponding heat flow map prepared from the averaged thermal conductivities and thermal gradients from the CPD reveals the existence of one low heat flow zone (75 mW/m2) over the center of Thrace Basin, and two high heat flow zones over the Istranca Masif (100–125 mW/m2) in the northern side and Saros Graben (125–135 mW/m2) areas in the southern side of the Thrace Basin.