[1] This paper shows how the Turkish-Iranian Plateau grows laterally by incrementally incorporating adjacent parts of the Zagros fold-and-thrust belt. The limit of significant, seismogenic, thrusting in the Zagros (M w > 5) occurs close to the regional 1250 m elevation contour. The seismicity cutoff is not a significant bedrock geology boundary. Elevations increase northward, toward regional plateau elevations of~2 km, implying that another process produced the extra elevation. Between the seismogenic limit of thrusting and the suture, this process is a plausibly ductile thickening of the basement, suggesting depth-dependent strain during compression. Similar depth-dependant crustal strain may explain why the Tibetan plateau has regional elevations~1500 m greater than the elevation limit of seismogenic thrusting at its margins. We estimate~68 km shortening across the Zagros Simply Folded Belt in the Fars region, and~120 km total shortening of the Arabian plate. The Dezful Embayment is a low strain zone in the western Zagros. Deformation is more intense to its northeast, in the Bakhtyari Culmination. The orogenic taper (across strike topographic gradient) across the Dezful Embayment is 0.0004, and across the Bakhtyari Culmination, 0.022. Lateral plateau growth is more pronounced farther east (Fars), where a more uniform structure has a taper of~0.010 up to elevations of~1750 m. A >100 km wide region of the Zagros further northeast has a taper of 0.002 and is effectively part of the Turkish-Iranian Plateau. Internal drainage enhances plateau development but is not a pre-requisite. Aspects of the seismicity, structure, and geomorphology of the Zagros do not support critical taper models for fold-and-thrust belts.

Oblique plate convergence is common, but it is not clear how the obliquity is achieved by continental fold‐and‐thrust belts. We address this problem in the Qilian Shan, northeastern Tibetan Plateau, using fieldwork observations, geomorphic analysis, and elastic dislocation modeling of published geodetic data. A thrust dips SSW from the northern range front and underlies steeper thrusts in the interior. Cenozoic thrust‐related shortening across the Qilian Shan is ~155–175 km, based on two transects. Elastic dislocation modeling indicates that horizontal strain in the interseismic period is consistent with oblique slip on a single low‐angle detachment thrust below ~26 km depth, dipping SSW at ~17°. We suggest that this detachment is located above North China Block crust, originally underthrust during Paleozoic orogeny. Horizontal shear strain is localized directly above the updip limit of creep on the detachment and is coincident with the left‐lateral Haiyuan Fault. This configuration implies that oblique slip on the detachment below seismogenic depths is partitioned in the shallow crust onto separate strike‐slip and thrust faults. This is consistent with strain partitioning in oceanic subduction zones but has not previously been found by dislocation models of continental interiors. The marginal, strike‐slip, Altyn Tagh Fault influences thrusting within the Qilian Shan for 100–200 km from the fault but does not control the regional structure, where Paleozoic basement faults have been reactivated. The Qilian Shan resembles the main Tibetan Plateau in nascent form: active thrusts are marginal to an interior that is developing plateau characteristics, involving low relief, and low seismicity.

Climate and tectonics have complex feedback systems which are difficult to resolve and remain controversial. Here we propose a new climate-independent approach to constrain regional Andean surface uplift. 87Sr/86Sr and 143Nd/144Nd ratios of Quaternary frontal-arc lavas from the Andean Plateau are distinctly crustal (>0.705 and <0.5125, respectively) compared to non-plateau arc lavas, which we identify as a plateau discriminant. Strong linear correlations exist between smoothed elevation and 87Sr/86Sr (R2 = 0.858, n = 17) and 143Nd/144Nd (R2 = 0.919, n = 16) ratios of non-plateau arc lavas. These relationships are used to constrain 200 Myr of surface uplift history for the Western Cordillera (present elevation 4200 ± 516 m). Between 16 and 26°S, Miocene to recent arc lavas have comparable isotopic signatures, which we infer indicates that current elevations were attained in the Western Cordillera from 23 Ma. From 23–10 Ma, surface uplift gradually propagated southwards by ~400 km.

S U M M A R YWe report five new 40 Ar/ 39 Ar 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), Tendürek 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 ∼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 (∼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 ∼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.In this paper we explore the relationships between tectonics, magmatism and landscape evolution in the Turkish-Iranian plateau, northwest Iran, to understand better the development of such orogenic plateaux in general.Orogenic plateaux are constructed as a result of subduction at convergent continental margins or continent-continent collision. The Tibetan and Turkish-Iranian plateaux are formed by the India-Eurasia and Arabia-Eurasia collisions, respectively (Hatzfeld & Molnar 2010), and are first-order geomorphic features of the Eurasian landscape. However their tectonic evolution and surface uplift history are not clearly understood, even though there may be consequences for climate on regional if not global levels (Raymo et al. 1988;Molnar et al. 2010). This paper presents new 40 Ar/ 39 Ar ages for lavas in the Maku region of northwest Iran (Figs 1 and 2), within the Turkish-Iranian plateau. The sampled lavas have an unusual setting: they travelled through pre-existing river valleys for tens of kilometres. After eruption, the valleys were reoccupied by the present rivers, which have cut gorges on the scale of 10-50 m through the lavas. Therefore the 40 Ar/ 39 Ar ages allow determination of fluvial incision rates at the sample sites, and help constrain the landscape evolution of this part of the Turkish-Iranian plateau, before and after the eruptions. Such information is valuable not only because it explains why the development of topographic relief, but because this evolution relates directly back to tectonic, climatic and magmatic processes that operate on geological timescales.However, it is typically difficult to obtain informat...

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