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[1] The Tian Shan Mountains constitute central Asia's longest and highest mountain range. Understanding their Cenozoic uplift history thus bears on mountain building processes in general, and on how deformation has occurred under the influence of the India-Asia collision in particular. In order to help decipher the uplift history of the Tian Shan, we collected 970 samples for magnetostratigraphic analysis along a 4571-m-thick section at the Jingou River (Xinjiang Province, China). Stepwise alternating field and thermal demagnetization isolate a linear magnetization component that is interpreted as primary. From this component, a magnetostratigraphic column composed of 67 polarity chrons are correlated with the reference geomagnetic polarity timescale between $1 Ma and $23.6 Ma, with some uncertainty below $21 Ma. This correlation places precise temporal control on the Neogene stratigraphy of the southern Junggar Basin and provides evidence for two significant stepwise increases in sediment accumulation rate at $16-15 Ma and $11 -10 Ma. Rock magnetic parameters also undergo important changes at $16-15 Ma and $11-10 Ma that correlate with changes in sedimentary depositional environments. Together with previous work, we conclude that growth history of the modern Tian Shan Mountains includes two pulses of uplift and erosion at $16 -15 Ma and $11 -10 Ma. Middle to upper Tertiary rocks around the Tian Shan record very young (<$5 Ma) counterclockwise paleomagnetic rotations, on the order of 15°to 20°, which are interpreted as because of strain partitioning with a component of sinistral shear that localized rotations in the piedmont.

The structure and dynamic evolution of a mountain belt piedmont are controlled by strong interactions between tectonics, surface processes (erosion, sedimentation), and climate. Studying these couplings relies on detailed geometric and kinematic analysis of morphostructural markers (folds, faults, terraces, alluvial surfaces) and analysis of syntectonic sedimentation. To study quantitatively how these markers form, evolve and record deformation, we developed a new analogue modelling approach using a specific composite granular material. The originality stands in the simultaneous modelling of orogenic deformation mechanisms and erosion-transport-sedimentation processes, but also in the use of techniques allowing quantitative measurement of morphostructural evolution. This methodology opens new perspectives in the fields of geomorphology (relief dynamics), seismotectonics (study of active faults), and sedimentology (including sequential stratigraphy).

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The Huallaga Basin is a deformed foreland basin located in North Peru. The basin comprises several syntectonic depocenters. The most significant is the Biabo Syncline located at the back of the Chazuta Thrust, a long, flat-floored thrust detaching on an evaporitic décollement, which has accommodated more than 40 km of horizontal displacement. The hangingwall of the Chazuta Thrust has remained remarkably intact with little or no internal deformation and has incorporated a large volume of evaporites at its base.In order to unravel the formation and evolution of this thrust, we conducted a series of physical experiments that tested the role of various parameters. The goal is to investigate a system in which most of the deformation is accommodated in the frontal part of the chain (Chazuta Thrust), whereas deformation of the thrust sheet itself remains minor.Results from our experimental investigations suggest that the three key parameters that have allowed for such a long-lived, large-slip frontal thrust to operate are (1) the wedgeshaped syn-kinematic sedimentation, (2) the presence of the Biabo Syncline, which acted as a bulldozer pushing the evaporites forward, forcing their distal inflation and (3) the erosion at the front that favored farther advance of the frontal thrust, dragging passively large volumes of evaporites along with it.