This paper is dedicated to the memory of the late Mehmet Ozan Sungurlu (1939-1990) for his immense contributions to our understanding of the geology of Turkey.
The Istanbul region is a part of a bigger continental fragment called the Rhodope-Pontide Fragment. Within this continental fragment, the Istanbul Zone consists, at the base, of a Neoproterozoic middle to high-grade crystalline rocks with relicts of volcanic arc and continental crust, which are not observed in Istanbul itself, but farther east near Zonguldak. This basement is overlain by a continuous, well-developed sedimentary sequence extending from the Lower Ordovician to the Lower Carboniferous. The Carboniferous flysch marks the progress of a shortening event. This event led to the folding and faulting of the Palaeozoic sequence which was intruded by an uppermost Permian granitoid and unconformably overlain by the Upper Permian to Lower Triassic red sandstones and conglomerates. The Triassic series is better formed east of Istanbul showing a typical transgressive development. The Jurassic sequence is absent, most likely as a result of the closure of the Palaeo-Tethys and the resultant generation of the Cimmerides. There is a small outcrop of Lower Cretaceous shallow marine sedimentary rocks and a much more widespread Upper Cretaceous-Lower Eocene clastic, carbonate and andesitic volcanic rocks unconformably covering the Palaeozoic, Triassic and Lower Cretaceous rocks. The pre-Bartonian closure of the Intra-Pontide suture along the Istanbul Zone as a consequence of its collision with the Sakarya Continent created another episode of shortening in this area, an event that was part of the Alpide evolution. The Intra-Pontide suture is the boundary between the Istanbul and Sakarya magmatic arcs in northwestern Turkey. During the Cainozoic, the first post-orogenic structures are Lutetian-Bartonian nummulitic limestones, which themselves are covered by a Paratethyan sequence of Miocene limestones and sandstones of mainly the Vallesian Stage, which include the Küçükçekmece vertebrate bearing horizon. The Pliocene is entirely fluviatile terrestrial clastics. The Pleistocene was deposited on an erosion surface which later became warped and into which the originally fluvial valley of the Bosphorus was entrenched. This valley was invaded by the Sea during the Holocene and caused the refilling of the Black Sea.
In southeastern Turkey, the NE-trending Antakya Graben forms an asymmetric depression filled by Pliocene marine siliciclastic sediment, Pleistocene to Recent fluvial terrace sediment, and alluvium. Along the Mediterranean coast of the graben, marine terrace deposits sit at different elevations ranging from 2 to 180 m above present sea level, with ages ranging from MIS 2 to 11. A multisegmented, dominantly sinistral fault lying along the graben may connect the Cyprus Arc in the west to the Amik Triple Junction on the Dead Sea Fault (DSF) in the east. Normal faults, which are younger than the sinistral ones, bound the graben's southeastern margin. The westward escape of the continental İskenderun Block, delimited by sinistral fault segments belonging to the DSF in the east and the Eastern Anatolian Fault in the north caused the development of a sinistral transtensional tectonic regime, which has opened the Antakya Graben since the Pliocene. In the later stages of this opening, normal faults developed along the southeastern margin that caused the graben to tilt to the southwest, leading to differential uplift of Mediterranean coastal terraces. Most of these normal faults remain active. In addition to these tectonic movements, Pleistocene sea level changes in the Mediterranean affected the geomorphological evolution of the area.
To the memory of Nicholas John (Nick) Archibald (1951−2014), master of cratonic geology. Cratons, defined by their resistance to deformation, are guardians of crustal and lithospheric material over billion-year time scales. Archean and Proterozoic rocks can be found in many places on earth, but not all of them represent cratonic areas. Some of these old terrains, inappropriately termed “cratons” by some, have been parts of mobile belts and have experienced widespread deformations in response to mantle-plume-generated thermal weakening, uplift and consequent extension and/or various plate boundary deformations well into the Phanerozoic. It is a common misconception that cratons consist only of metamorphosed crystalline rocks at their surface, as shown by the indiscriminate designation of them by many as “shields.” Our compilation shows that this conviction is not completely true. Some recent models argue that craton formation results from crustal thickening caused by shortening and subsequent removal of the upper crust by erosion. This process would expose a high-grade metamorphic crust at the surface, but greenschist-grade metamorphic rocks and even unmetamorphosed supracrustal sedimentary rocks are widespread on some cratonic surfaces today, showing that craton formation does not require total removal of the upper crust. Instead, the granulitization of the roots of arcs may have been responsible for weighing down the collided and thickened pieces and keeping their top surfaces usually near sea level. In this study, we review the nature and origin of cratons on four well-studied examples. The Superior Province (the Canadian Shield), the Barberton Mountain (Kaapvaal province, South Africa), and the Yilgarn province (Western Australia) show the diversity of rocks with different origin and metamorphic degree at their surface. These fairly extensive examples are chosen because they are typical. It would have been impractical to review the entire extant cratonic surfaces on earth today. We chose the inappropriately named North China “Craton” to discuss the requirements to be classified as a craton.
If negative buoyancy of subducted lithosphere pulling slabs into the mantle is the prime driver of plate tectonics, as widely thought (
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