Forearc high uplift by deep crustal flow during growth of the Anatolian margin

We present a model for the dynamic formation of the forearc high of southern Anatolia where sedimentation in the forearc basin leads to thermally-activated deformation in the lower crust. Our thermo-mechanical models demonstrate that forearc sedimentation increases the temperature of the underlying crust by “blanketing” the heat flux and increasing Moho depth. Deformation switches from frictional to viscous with a higher strain rate led by increased temperature. Viscous deformation changes large-wavelength subsidence into coeval, shortwavelength uplift and subsidence. Models show that forearc highs are intrinsic to accretionary wedges and can grow dynamically and non-linearly at rates dependent on sediment accretion, sedimentation and temperature. The mechanism explains Neogene first-order upper-plate strain and vertical motions in the Anatolian margin along Central Cyprus, and in the orogenic plateau margin in South Turkey. This system is analogous to forearc highs in other mature accretionary margins, like Cascadia, Lesser Antilles or Nankai. keywords: forearc high; plateau margin; subduction zone; subduction wedge; uplift; Central Anatolian Plateau


Introduction
1 Climatic and geodynamic processes are the first-order drivers of topography in orogenic 2 plateaus and plateau margins. However, mechanisms for detailed patterns of uplift in orogenic 3 plateau systems, such as Himalaya-Tibet and Puna-Altiplano (e.g., Allmendinger et al., 1997; 4 Molnar, 1984) remain diverse and difficult to generalize. This is also true for the history of 5 topography growth of the orogenic plateau of Central Anatolia and its margins. While 6 continental delamination (Bartol and Govers, 2014) or lithospheric drip (Göğüş et al., 2017) 7 have been suggested to sustain Central Anatolia low relief at ~1 km, its plateau margins are 8 geodynamically different; transpressional orogenic uplift may have formed the northern margin 9 (Yildirim et al., 2011) whereas the southern margin is strongly influenced by the Cyprus 10 subduction zone to the south. The formation mechanism of the latter is of particular interest, for 11 the uplift in the southern margin has a limited N-S extent and occurred in the absence of

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We also track the horizontal distance between the highest and lowest point of the forearc 245 basement during the last stages of model run, i.e. the period of differentiation in vertical 246 motions as led by sedimentation (Fig. 6, Inset B). For all simulations, the horizontal distance 247 between the highest point on the forearc high and the lowest point on its depocenter is short 248 (<70 km) with regards to its associated vertical motion (up to >12 km). Such horizontal distance 249 is also controlled by a threshold value in sedimentation rate (Fig. 6, Inset B); whereas models 250 with lower sedimentation rates lead to horizontal distances of ~20 km that are consistent 251 throughout the model run, those with higher sedimentation rates show horizontal distances 252 between 40 km and 70 km that vary during the model run. For the latter simulations, once 253 vertical motions onset, horizontal distances for the tracked points increase suddenly for a 254 period of ~3 Ma and decrease thereon for the rest of the model run (Fig. 6, Inset B). These

Sediment blanketing controls on temperature and viscosity 264
We derive the evolution in time of temperature and viscosity (Fig. 7)

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Sedimentation rates control the growth of a forearc high in mature accretionary wedges, 289 and the rate of associated topographic growth, ultimately leading to regional vertical motions of 290 opposite sense and short wavelength (Fig. 6). The correlation of increased sedimentation rates 291 with larger relative vertical motions in the forearc high as well as with increased temperatures 292 and lower viscosity below it (Fig. 7) strongly support that sediments have a "thermal 293 blanketing" effect that induces viscous flow in the lower crust and the uplift of the forearc high.   Williams et al., (1994) and as decoupled-to-coupled flow in Royden (1996).

Growth of the Anatolian margin 361
Our simulations are consistent with SCAP formation as a dynamic, thermo-viscous forearc high 362 led by forearc sedimentation and accretion along Central Cyprus (Fig. 8) Values along the section of interest derived from the two major gravimetric studies in the area (Ates et al., 1999;Ergün et al., 2005). (C) Published geophysical data, including the interpretation of the offshore section C in Ergün et al. (2005), and that of the seismic study performed by Mart & Ryan (2002). The plot also include several cross-sectional values retrieved from maps of Moho depth models derived from different geophysical approaches, including Pn tomography and receiver functions (Abgarmi et al., 2017;Delph et al., 2017;Koulakov and Sobolev, 2006