Asymptomatic lithospheric drip driving subsidence of Konya Basin, Central Anatolia

Geological and geophysical observations show instances of surface subsidence, uplift, shortening, and missing mantle lithosphere inferred as manifestations of the large-scale removal of the lower lithosphere. This process—specifically by viscous instability or lithospheric “drips” —is thought to be responsible for the removal or thinning of the lithosphere in plate hinterland settings such as: Anatolia, Tibet, Colorado Plateau and the Andes. In this study, we conduct a series of scaled, 3D analogue/laboratory experiments of modeled lithospheric instability with quantitative analyses using the high-resolution Particle Image Velocimetry (PIV) and digital photogrammetry techniques. Experimental outcomes reveal that a lithospheric drip may be either ‘symptomatic’ or ‘asymptomatic’ depending on the magnitude and style of recorded surface strain. Notably, this is controlled by the degree of coupling between the downwelling lithosphere and the overlying upper mantle lithosphere. A symptomatic drip will produce subsidence followed by uplift and thickening/shortening creating distinct ‘wrinkle-like’ structures in the upper crust. However, the ‘symptoms’ of an asymptomatic drip are subdued as it only yields subsidence or uplift, with no evidence of shortening in the upper crust. Here, we combine analogue modelling results with geological and geophysical data to demonstrate that the Konya Basin in Central Anatolia (Turkey) is one such example of an asymptomatic drip. Global Navigation Satellite System (GNSS) measurements reveal elevated vertical subsidence rates (up to 50 mm/yr) but no well-documented crustal strain or structural features such as fold-and-thrust belts. This work demonstrates that different types of lithospheric drips may exist since the Archean, and there may be instances where the mantle lithosphere is dripping with no distinct manifestations of such a process in the upper crust.