DRIP TECTONICS AND THE DRIVERS OF PROTO-PLATEAU DEVELOPMENT IN COLLISIONAL OROGENS ­– INSIGHTS FROM CENTRAL ANATOLIA

Anatolia is located centrally within the Tethyan orogen, which spans from the Atlantic to the Pacific Ocean. Today, this orogenic system is defined by stepped topography – beginning at sea level in the west due to modern backarc extension in the Mediterranean Sea as Africa impinges on Europe and culminating in the east with ongoing intercontinental collision between India and Asia forming the 5 km high, low relief, 2.5 million km² Tibetan plateau. We define the low relief interior of Central Anatolia as a proto-plateau because it resides centrally between such modern end members and importantly exhibits 1/5 the surface elevation and an order of magnitude less low relief surface area than the Tibetan Plateau. However, despite the plateaus’ differences in elevation, surface area, and crustal thickness, colloquially referred to as ‘collisional maturity’, tomographic cross sections demonstrate both regions are devoid of their underlying lithospheric mantle. Based on such observations we investigated when, where, and how lithospheric mantle was removed beneath the Central Anatolian proto-Plateau. Our detrital zircon U-Pb and Hf results point to significant weakening of upper-plate lithospheric mantle as a consequence of either slab breakoff or transient trench retreat from 55–45 Ma, followed by rapid thickening and oroclinal bending of the northern Neotethyan Izmir-Ankara-Erzincan suture zone from 45–35 Ma that culminated with wholesale lithospheric removal shortly after ~35 Ma. In turn, a similar sequence of events describes the late Neogene evolution of the southern Neotethyan Inner-Tauride suture zone, where slab breakoff or transient trench retreat from 9–7 Ma was followed by a magmatic lull until ~1 Ma that culminated with wholesale lithospheric removal. Such interpretations are supported along both suture zones within the Central Anatolian proto-Plateau by the deposition of lacustrine rocks over 10–20 thousand km² during crustal thickening or magmatic lulls, followed by adakite magmatism, upper-plate extension, the uplift of basin margins, and fluvial reorganization. Based on such observations, we propose multiple phases of lithospheric removal along suture zones are integral to the early formation of moderate elevation, low-relief plateau interiors from Anatolia to Asia.