The Moroccan High Atlas, the Anti-Atlas belts, and the Siroua volcanic massif form an orographic system locally risen to elevations over 4 km. Topographic growth of this system occurred by Cenozoic transpressive inversion of Mesozoic rift structures concomitant with volcanic activity and related mantle processes. In order to constrain the topographic growth, we analyze the regional-scale exhumation pattern, and we compare it to physiographic features. We contribute 35 new mean (U-Th-Sm)/He and 24 new fission track ages on apatite from the High Atlas and Anti-Atlas, which all together range from 196 to 5 Ma. In the Anti-Atlas, we find that the rate and amount of Cenozoic exhumation are <0.05 km/Ma and 2 km, respectively. In the High Atlas, our new data together with previous ones show that the axial regions feature the highest topography, relief, channel steepness, and orographic precipitations together with the maximum rate and amount of Cenozoic exhumation, in the range of 0.2-0.3 km/Ma and 4-6 km, respectively. This region is bounded by high-angle oblique-slip faults, which display a Neogene vertical motion of a few kilometers. Moreover, the most deeply incised valley in the axial region of the High Atlas shows stepwise cooling and exhumation with a final acceleration after 6 Ma. We conclude that the location in the same region of high river channel steepness, topography, orographic precipitations, and rates and amount of exhumation, together with large vertical offsets along oblique-slip faults, suggests that crustal deformation may exert a major control on the topographic growth of Atlas orographic swell.

The High Atlas of Morocco is a double-vergent mountain belt developed by Cenozoic shortening and inversion of a Triassic-Jurassic rift. The structural setting, the morphometric features, and the patterns of exhumation through time and space change remarkably both along and across the strike. Here we combine structural data with revised thermochronological data to unravel the kinematic and evolution of the western High Atlas. Our results show that the structural grain of the western High Atlas is defined by two main groups of faults, namely, thrust and oblique-slip faults, which mainly strike subparallel from W-E to NE-SW. The slip direction of the thrust structures is NNW-SSE to NW-SE oriented, and the slip direction of the oblique-slip faults is WSW-ENE to NW-SE oriented. Pieces of thermochronological and geological evidence indicate that in the last~10 Ma the exhumation rate increased during the activity thrusts and oblique-slip faults. The coexistence of these two fault systems also suggests partitioning of deformation under a transpressive regime. In the western High Atlas, we estimate a displacement of~12 km on the frontal thrusts and of at least~22 km on the axial oblique-slip structures. Thrusts and oblique-slip structures together result in a total cumulative displacement of~25 km, which represents about half of the Africa-Eurasia convergence.

Extension of the crust generates normal faults and basins where sediments are trapped. Morphologically, extensional basins are generally classified as internally (endorheic) or externally (exorheic) drained. In the case of an internally drained basin, sediments are transported and stored within it. If the basin is externally drained, sediments are transported out of the basin and deposited in distal regions. The internally drained stage of extensional basins is generally a transient feature as these basins often evolve into an externally drained basin. Endorheic-exorheic and exorheic-endorheic transitions have been documented in several rifts basins, in compressional and extensional settings, to unravel the feedback between sedimentation-erosion-climate and tectonics (e.g.,

Stratigraphic and thermochronologic data are used to study the processes that shaped the topography of the central Apennines of Italy. These are part of a major, active mountain belt in the center of the Mediterranean area, where several subduction zones control a complex topography. The Apennines were shaped by contraction at the front of the accretionary wedge overlying the subducting Adria microplate followed by extension at the wedge rear in response to eastward slab roll-back. In the central Apennines, intermontane extensional basins on the western flank rise eastward toward the summit. We contribute with new data consisting of 28 (U-Th-Sm)/He and 10 fission track ages on apatites to resolve a complex pattern of thermal histories in time and space, which we interpret as reflecting the transitional state of the orogen, undergoing a two-phase evolution related to initial slab retreat, followed by slab detachment. Along the Tyrrhenian coast, we document cooling from depths ≥3−4 km occurring between 8 and 5 Ma and related to the opening of marine extensional basins. Post−5 Ma, a broader region of the central Apennines exhibits cooling from variable depths, between &lt;2 km in most areas and ≥3−4 km in the northeast, and with different onset times: at ca. 4 Ma in the west, at ca. 2.5 Ma in the center and northeast, and at ca. 1 Ma in the southeast. Between 5 and 2.5 Ma, exhumation is associated with modest topographic growth during the late stages of thrusting. Since 2.5 Ma, exhumation has concurred with the opening of intermontane basins in the west and in the east, with regional topographic growth and erosion, that we interpret to be associated with the locally detaching slab.