International audienceThe Ama Drime range located at the transition between the high Himalayan range and south Tibet is a N-S active horst that offsets the South Tibetan Detachment System (STDS). Within the horst, a paragneissic unit, possibly attributed to the upper Himalayan crystalline series, overly the lower Himalayan crystalline series Ama Drime orthogneissic unit containing large metabasite layers and pods that have experienced pressure >= 1.4 GPa. Combining structural analysis with new and published pressure-temperature (P-T) estimates as well as U-Th/Pb, Ar-39/Ar-40 and (U-Th)/He ages, the P-T-deformation-time (P-T-D-t) paths of the main units within and on both sides of the horst are reconstructed. They imply that N-S normal faults initiated prior to 11 Ma and have accounted for a total exhumation <= 0.6 GPa (22 km) that probably occurred in two phases: the first one until similar to 9 Ma and the second one since 6 to 4 Ma at a rate of similar to 1 mm/yr. In the Ama Drime unit, 1 to 1.3 GPa (37 to 48 km) of exhumation occurred after partial melting since similar to 30 Ma until similar to 13 Ma, above the Main Central Trust (MCT) and below the STDS when these two fault systems were active together. The switch from E-W (STDS) to N-S (Ama Drime horst) normal faulting between 13 and 12 Ma occurs at the time of propagation of thrusting from the MCT to the Main Boundary Thrust. These data are in favor of a wedge extrusion or thrust system rather than a crustal flow model for the building of the Himalaya. We propose that the kinematics of south Tibet Cenozoic extension phases is fundamentally driven by the direction and rate of India underthrusting

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The presence of ~NS‐trending rifts within the Tibetan Plateau attests that it is undergoing ~EW extension. In southern Tibet, the total extension rate, distributed across seven main rifts over a distance of ~1,000 km, has been inferred to amount to about half of the shortening rate across the Himalayas. Quantifying the late Quaternary extension rates across the largest rift (Yadong‐Gulu rift [YGR]) is important to understand Tibetan deformation and to discuss the high plateau evolution during the later stages of continental collision. We performed 10Be surface‐exposure cosmogenic nuclide dating of 57 samples from three fluvial surfaces and two moraines that are vertically offset by the normal faults bounding the northern YGR. After carefully assessing individual ages at each site, to elucidate scatter in the age distributions, we obtained ~EW extension rates of up to 3–6 mm/yr near the northern end of the rift (Gulu) and of only 1.3 ± 0.3 mm/yr in the south (Yangbajing). The fast rates in the north may be influenced by dextral slip along the Beng Co fault, whose rate ought to be at least 6.0 ± 1.8 mm/yr. The total late Quaternary extension rate of 9 ± 2 mm/yr we infer across southern Tibet between ~81°E and 92°E, assuming similar rates across each rift, is similar to earlier, qualitative inferences and consistent with recent geodetic results. Distinct deformation rates north and south of the Bangong‐Nujiang suture may reflect significant differences between the extensional kinematics and mechanisms across the Qiangtang and Lhasa blocks.

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Assessment of sediment redistribution by end-Ordovician ice sheets is crucial for the reconstruction of Lower Paleozoic source-to-sink patterns. Focussing on the ice-distal, deepwater Tazekka depocenter (Moroccan Meseta), we thus performed a provenance study that combined whole-rock geochemistry, petrography and insights from highresolution detrital zircon ages. The results show that the glacigenic sediments are compositionally-mineralogically and geochemically-more mature than preglacial strata. This observation points to a preferential cannibalization of the "great Lower Paleozoic quartz-rich sandstone sheet", with a limited input of first-cycle, far-travelled clastic sediments. Differentiation of glacial units is not straightforward, yet the glaciation acme is typified by a highly mature sedimentary source and an age spectrum lacking Mesoproterozoic zircon grains, both features strongly indicating derivation from the Cambrian-Lower Ordovician cover of the Tuareg Shield. More regional sources are expressed during the earlier glaciation stages, during which lowstand remobilisations unrelated to subglacial erosion are also suspected. Subordinate but notable late Tonian (∼ 0.8 Ga) and latest Stenian to early Tonian (∼1 Ga) zircon populations are also evidenced in Morocco, which may have implications for future paleogeographic reconstructions.

The Charnath Khola is a large river crossing the Himalayan thrust system in the region devastated by the great M8.3 1934 Bihar‐Nepal earthquake. Fluvial terraces are abandoned along the river and at the base of a ~20‐m high cumulative thrust escarpment. A trench across the fault scarp exposed Siwalik mudstone/siltstone overthrusting Quaternary units and three colluvial wedges interfingered with fluvial sands. The 85 accelerator mass spectrometry radiocarbon dates, from detrital charcoals sampled in the trench, a river cut and river terraces, constrain the timing of the sedimentary processes following the last two major earthquakes, in 1934 and 1255 CE. Although several samples straddle the main earthquake horizon, associating it with the 1934 earthquake, based solely on radiocarbon ages, remains challenging. The 49 detrital charcoal ages found in the pre‐earthquake and postearthquake units fall between 65 and 225 BP, a period with a flat calibration curve. Many of these radiocarbon ages are suspected to include a part due to inbuilt time (i.e., age of the wood at the time of burning), transport time, and reworking processes, which are difficult to resolve. Considering these ages at their face value could lead to dates older than the actual earthquake dates. We suggest that a part of this chronological bias is also related to a local postseismic aggradation pulse of 4 to 5 m of sediments, which is documented in the trench and terraces. This fluvial sequence, hiding the most recent surface rupture, is likely related to landslide‐sediment deposition triggered by the 1934 Bihar‐Nepal earthquake.

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