40Ar/39Ar dating of Quaternary lavas in northwest Iran: constraints on the landscape evolution and incision rates of the Turkish-Iranian plateau

P>We report five new 40Ar/39Ar ages for basaltic lavas in the Maku region of northwest Iran, between ca. 1.87 and 0.40 Ma, which help constrain the tectonic and landscape evolution of this part of the Turkish-Iranian plateau. Flows originated from the composite volcanoes Ararat (Agri Dagi), Tendurek and Yigit Dagi, in eastern Turkey (Anatolia). These volcanoes are within the Turkish-Iranian plateau, which is a consequence of the Arabia-Eurasia collision, but has a poorly constrained evolution and surface uplift history. Current plateau elevations are typically 1.5-2 km, and relief between non-volcanic summits and basins is typically on the scale of similar to 1 km. Samples are from flows that passed along pre-existing river valleys. Gorges were cut by re-established rivers after the eruptions, but the great majority of the local relief (similar to 95 per cent) lies above the sampled flows and so most likely pre-dates the volcanism. Gorge depths and lava ages allow local Quaternary fluvial incision rates to be calculated, which are similar to 0.01 to 0.05 mm yr-1. These rates imply slow surface uplift of this part of the Turkish-Iranian plateau during the Quaternary. We therefore constrain the generation of the great majority of relief in the study area to be pre-Quaternary, and caused by the tectonic construction of the plateau, rather than a subcrustal origin related to the Quaternary magmatism.