Neogene Kinematics of the Potwar Plateau and the Salt Range, NW Himalayan Front: A Paleostress Inversion and AMS study

We provide new kinematic data from the Potwar Plateau (Pakistan) to evaluate the tectonic evolution of the region during the Neogene. The plateau is bound by two major strike-slip faults in the west and the east, accommodating its southwards translation. We have recognized two Neogene deformation phases in the plateau, based on paleostress inversion and Anisotropy of Magnetic Susceptibility (AMS) tensors. The first phase lasted until the early Pliocene and was characterized by vertical minor stress and N-S compression, implying thrust tectonics. The second deformation phase is characterized by a near-vertical intermediate principal stress and near-horizontal major and minor stresses, interpreted to be associated with strike-slip tectonics since the late Pliocene. K-int vectors from 21 sites are relatively compatible with the major principal stress orientations (sigma(1)) and indicate two distinct domains. This is possibly because K-min orientations are related to compaction, whereas K-int orientations were always parallel to tectonic shortening and hence compression direction during both strike-slip (post-late Pliocene) and thrusting (pre-late Pliocene) phases. These phases are characterized by swapping of (sigma(2)) and (sigma(3)) orientations while (sigma(1)) maintained its orientation. The most prominent change occurs at the western part of the Potwar Plateau, where major principal stress directions (sigma(1)) and K-int axes fan out south-westwards. The eastern domain is dominated by NE-SW trending folds and thrust faults, which are absent in the western domain. These structural features are interpreted to be the result of the distribution of deposits of the Neoproterozoic Salt Range Formation as a substratum below the Potwar Plateau. The Salt Range Formation is very thick and widespread in the west area and almost absent in the east. This factor led to unconstrained southwards gliding of the Potwar Plateau over the salt deposits in the west as opposed to frictional sliding and substantial internal deformation in the east

Repeated reactivation of clogged permeable pathways in epithermal gold deposits : Kestanelik epithermal vein system, NW Turkey

This study presents a detailed study of the dimensions, geometry, textures and breccias of a well-exposed epithermal vein system, the Kestanelik gold deposit in the Biga Peninsula, NW Turkey and investigates the permeability enhancement mechanisms in epithermal gold deposits. Here mineralisation is associated with quartz veins up to 13.6 m thick. Vein textures and breccia components indicate repeated sealing and subsequent brecciation of wall rock and pre-existing vein infill. Field and petrographic analyses characterize E-W trending veins as left lateral faults, whilst NE- SW trending veins are extensional (Mode I) fractures. Cataclasite and tectonic breccia of wall rocks and early quartz, hydrothermal crackle breccias, and matrix supported chaotic breccias of pre- existing vein infill, all of which are cemented by late iron-oxide-bearing quartz, indicate that co- seismic rupturing and hydraulic fracturing are two major permeability enhancement mechanisms. In addition, transient variations in local stress direction, caused by syn-mineralisation dyke intrusion, may have enhanced permeability on mis-oriented surfaces and at locations where the dip changes. This study emphasizes the importance of understanding structural geology and kinematics as controls on the location of boiling and mineralisation mechanisms in epithermal gold deposits

Tectonic evolution and paleogeography of the Kırşehir Block and the Central Anatolian Ophiolites, Turkey

In Central and Western Anatolia two continent-derived massifs simultaneously underthrusted an oceanic lithosphere in the Cretaceous and ended up with very contrasting metamorphic grades: high pressure, low temperature in the Tavsanli zone and the low pressure, high temperature in the Kirsehir Block. To assess why, we reconstruct the Cretaceous paleogeography and plate configuration of Central Anatolia using structural, metamorphic, and geochronological constraints and Africa-Europe plate reconstructions. We review and provide new Ar-40/Ar-39 and U/Pb ages from Central Anatolian metamorphic and magmatic rocks and ophiolites and show new paleomagnetic data on the paleo-ridge orientation in a Central Anatolian Ophiolite. Intraoceanic subduction that formed within the Neotethys around 100-90 Ma along connected N-S and E-W striking segments was followed by overriding oceanic plate extension. Already during suprasubduction zone ocean spreading, continental subduction started. We show that the complex geology of central and southern Turkey can at first order be explained by a foreland-propagating thrusting of upper crustal nappes derived from a downgoing, dominantly continental lithosphere: the Kirsehir Block and Tavsanli zone accreted around 85 Ma, the Afyon zone around 65 Ma, and Taurides accretion continued until after the middle Eocene. We find no argument for Late Cretaceous subduction initiation within a conceptual "Inner Tauride Ocean" between the Kirsehir Block and the Afyon zone as widely inferred. We propose that the major contrast in metamorphic grade between the Kirsehir Block and the Tavsanli zone primarily results from a major contrast in subduction obliquity and the associated burial rates, higher temperature being reached upon higher subduction obliquity.European Research Council ; Netherlands Organization for Scientific Research (NWO

Kinematic development and paleostress analysis of the Denizli Basin (Western Turkey): implications of spatial variation of relative paleostress magnitudes and orientations

Paleostress orientations and relative paleostress magnitudes (stress ratios). determined by using the reduced stress concept. are used to improve the understanding of the kinematic characteristics of the Denizli Basin. Two different dominant extension directions were determined using fault-slip data and travertine fissure orientations. In addition to their stratigraphically coeval occurrence. the almost exact fit of the sigma(2) and sigma(3) orientations for the NE-SW and NW-SE extension directions in the Late Miocene to Recent units indicate that these two extension directions are a manifestation of stress permutations in the region and are contemporaneous. This relationship is also demonstrated by the presence of actively developing NE-SW and NW-SE elongated grabens developed as the result of NIE-SW and NW-SE directed extension in the region. Moreover, stress ratios plots indicate the presence of a zone of major stress ratio changes that are attributed to the interference of graben systems in the region. It is concluded that the plotting of stress orientations and distribution of stress ratios is a useful tool for detecting major differences in stress magnitudes over an area. the boundaries of which may indicate important Subsurface structures that cannot be observed on the surface

DERİN SİSMİK YANSIMA VERİLERİ IŞIĞINDA KARADENİZ HAVZASININ JEOLOJİSİ VE TEKTONİĞİ

Karadeniz Batı ve Doğu Karadeniz olmak üzere iki alt havzadan oluşmaktadır. Bunlardan Batı Karadeniz Havzası Erken Kretasede, Doğu Karadeniz ise Geç Kretase sonunda, yaklaşık olarak 60 My önce, yelpaze şeklinde dönerek açılmışlardır. Her iki alt havza Andrusov ve Archangelsy sırtları boyunca bir birlerinden ayrılırlar. Batı Karadeniz havzası İstanbul Bloğunun Moezyadan ve onunla bitişik olan Sakarya Bloğunun bir kısmının Scythia platformundan kopması ve güneye saat yönünde dönmesi sonucu açılmıştır. Açılmaya neden olan hareket vektörünün dönme kutbu bu günkü coğrafik pozisyona göre Selanik civarındaki bir noktaya karşılık gelmektedir. Doğu Karadeniz havzası ise Andrusov sırtının Shatski bloğundan kopup, Kırımın batısındaki bir noktaya göre saat yönünde dönerek açılmıştır. Batı Karadeniz havzası tipik magma fakir kıta kenarı özellikleri gösterirken, Doğu Karadeniz havzası magma-zengin kıta kenarı özellikleri gösterir. Günümüzde Doğu Karadeniz havzası hemen hemen tüm doğu ve kuzey kısımlarında Büyük Kafkaslar havzasının terselmesine bağlı olarak sıkışma ve buna bağlı bindirme-kıvrım kuşakları ve ilgili önülke havzaları ile çevrilidir. İç kesimlerde, Batı Karadeniz Havzası güneyde kısmen gerilme ve doğrultu atımlı faylanma ile kuzey ve kuzeybatıda ise Tuna, Dinyeper ve Dinyester nehirleri ile ilgili hızlı sedimantasyona bağlı gravite yapıları ile karakterizedir. Derin sismik yansıma verilerinde Batı Karadeniz fayı, Trabzon, Rize fayları bariz olarak görülmektedir. Ayrıca Karadeniz ortası yükseliminin altına doğru dalma başlangıcına veya terk edilmiş dalma batma zonu işaretleri görülmektedir. Sıkışma yapılarının havzanın Kuzey kesimlerinde ve ince kabuk deformasyonu şeklinde gelişmesi yanında havzanın iç kısımlarda benzeri sıkışma yapılarının gelişmemiş olmaması, Karadeniz kabuğunun onu çevreleyen kıtasal kabuktan daha güçlü olduğunu göstermektedir. Bu nedenle, Karadeniz rijit blok olarak davranıp Arap Bloğunun çarpması ve kuzeye olan hareketi nedeniyle yarattığı güncel K-G sıkışma ve deformasyon havzanın kenarlarına yansıtılmış olup havza iç deformasyondan korunmuştur

Tectonic Characteristics and Evolution Banda Sea Region

Middle Miocene onwards, the Banda Sea started to be devolved due to retreat and roll-back of the northwards subducting Indo-Australian oceanic plate below the south-easternmost Eurasian margin. This process is facilitated by a trench perpendicular tear in the slab. The tear dissects Sulawesi Island along the Palu-Matana Fault and delimits the southern boundaries of Banggai-Sula, Birds Head (BH) and the northern boundary of Banda Sea plate. Dominantly, this structure is sinistral in nature from Celebes Sea up to an offshore point located half way between Seram and Misool Islands, which we think is the tip of the tear. To the east of this point, the deformation is dominated by thrusting and accretion that produce the so called Seram Accretionary Wedge (SAW). SAW extends and includes part of onshore Seram Island and extends into the Seram Trench and curves around the outer margin of Banda Arc including the Tanimbar, Jamdena and offshore Timor Leste. South of Obira Island is a quadruple junction where, four major structures namely Palu-Matana, Poh-Mangole, Seram, and Sorong fault zones meet. The Sorong Fault Zone (SFZ) separates the Birds Head (BH) and Halmahera and has accommodated more than 48 km sinistral off-set over the last few million years. In the NW margin of Cendrawasih Basin, Sorong and Yapen faults meet and the eastern boundary of BH is delimited by the Van Damen peninsula which comprises ultra high pressure metamorphic rocks with exhumation ages as young as 1 Ma. Earthquake focal mechanism solutions indicate that the eastern boundary of BH is linked with a large scale offshore normal fault related to the exhumation of the Van Damen peninsula that contribute to the development of Cendrawasih Basin (CB). The eastern margin of CB is a major transpressive belt along which BH and the main body of the bird (Papua & Irian Jaya) is decoupled. This implies that the Aru Basin which is located at the NE corner of Banda Arc is a FFT junction. In this contribution we will discuss the characteristics of the major structures around Banda Sea region and provide constraints on its evolution during the Neogene, based on satellite remotely sensing and recently acquired high resolution bathymetric images and 2D seismic profiles mainly from Celebes Sea, Makassar Strait, Gorontalo, Tomori, Bone, off-shore Seram-Aru, Kafiau-Misool corridor, Cendrawasih basins and Indonesian side (Jamdena and Roti) of the NW Australian Shelf

An Interpretation of the Basement Structure and Formation of the Black Sea Based on Deep Seismic Data and Gravity Modelling

It is widely accepted that the Black Sea consists of two separate back arc basins which opened at different times during the Cretaceous driven by northward subduction of the Neo-Tethys Ocean. The paucity of well data, complex geometries and seismic imaging challenges mean that questions remain regarding the basement architecture though most authors accept that, at least in part, both these basins are floored by oceanic crust, even though there a no magnetic stripes. Interpretation of deep, long offset SPAN seismic data (imaging to more than 30km) and integrated modelling of gravity data support the presence of oceanic crust and allow its distribution and that of stretched continental crust to be mapped in both the West and East Black Sea. We also investigate the architecture of the transitional zone between continental and oceanic realms and how it changes across the Black Sea. We note the absence of seaward dipping reflectors and only limited areas where there is good evidence for exposure of sub-continental mantle and discuss the implications this may have on the nature of Black Sea opening within the regional tectonic framework. The Black Sea is surrounded by fold and thrust belts. We will show some evidence to suggest that the beginnings of subduction of the oceanic crust can be seen beneath part of the mid Black Sea high, and that the original oblique outer marginal detachment on which the ocean opened is beginning to be inverted as a subduction zone with contractional deformation of the volcano-sedimentary pile in the outer marginal trough. Deep crustal structure is an important element in hydrocarbon maturation. The quantity of radiogenic heat generated by the upper continental crust depends on its thickness, and is therefore a direct function of the amount of stretching and the rift architecture. Other terrains provide generally much less heat into the base of the sedimentary system. We present maps of heat flow and radiogenic heat production which could provide direct and important inputs into petroleum systems models

Comment on 'Rockfall avalance deposits associated with normal faulting in the NW of the Cankiri basin: implications for the post-collisional tectonic evolution of the Neo-Tethyan suture zone' by G. Seyitoglu, N. Kazanci, L. Karadenizli, S. Sen, B. Varol, and T. Karabiyikoglu

Seyitoglu et al. (2000) described their interpretation, based on a single fault surface and rockfall avalanche deposits previously mapped as a W-vergent thrust klippen above the Neogene successions in the Hancili Basin, that in central Anatolia there was a single extensional basin throughout the Miocene - Early Pliocene. It was later fragmented by a structural high of Neo-Tethyan ophiolitic basement bounded by an E-vergent thrust fault in the east along the western margin of the Cankiri Basin and a west-dipping normal fault in the west along the eastern margin of the Hancili Basin, into two sub-basins - Cankiri and Hancili basins - subsequent to the activity along the Kirikkale-Erbaa splay of the North Anatolian Fault Zone in the Late Pliocene (Fig. 1b). They also concluded that the crustal extension commenced in the Early Miocene and continued until the Early Pliocene without a break. They further claimed that their contention is supported by the recent works of Kaymakci (2000) and Kaymakciet al. (2000)