[1] The Red River originates from SW China and SE Tibet and has a total length >1000 km. In this study, we present new U-Pb dating and Hf isotopic analysis of zircon grains, from both modern and paleoriver sands in order to constrain the provenance of the modern river and to decipher drainage evolution through time. Our data show that the Yangtze and Songpan Garze blocks are the most important sources for sediment, although this material is mostly reworked via younger sedimentary rocks in the upper reaches of the Red River. Sands in the Da River and to a lesser extent the Lo River have zircon ages indicating that they are minor contributors to the net flow, consistent with rock uplift, which is strongest in the upper reaches of the Red River, rather than precipitation being the primary control on erosion. Sediments eroded from the metamorphic rocks along the Red River Fault Zone appear to have made a greater contribution during the Miocene. Zircon ages suggest that the Red River flowed north of the Day Nui Con Voi in the Middle-Late Miocene. The Red River appears to have had a largely stable provenance since at least the Late Miocene. Upper Miocene sedimentary rocks NE of the Red River indicate the presence of a separate, large river in the Late Miocene. Hf isotope data indicate that the Irrawaddy River was never part of the Red River system. Although we do not exclude the Salween, Mekong, and Yangtze rivers from having been part of the Red River, any connection must have been pre-Middle Miocene.

Abstract:The Neogene-Quaternary infill of the Orava-Nowy Targ Intramontane Basin comprises two tiers showing contrasting lithologies. The Neogene tier is largely composed of claystones and siltstones, whereas the Quaternary tier is dominated by gravels. The two sequences are separated by an erosional surface underlain by a regolith. Deposition of the Neogene sequence took place during subsidence of the basin. No prominent relief existed in the area of the presentday mountains actually surrounding the basin at that time. The regolith started to form at the onset of basin inversion. Still, no prominent relief existed in the present-day mountains. The onset of deposition of Quaternary gravels in the basin corresponds to acceleration of uplift of the surrounding mountains, which has been continuing until now. The Pieniny Klippen Belt has been subject to erosion, at least locally, from the deposition of the basal part of the Neogene sequence filling the Orava-Nowy Targ Basin until present times. In contrast, the Paleogene cover of the Tatra Mts was removed only during the Quaternary.

The objectives of this contribution are: (1) promotion of application of fractured clasts analysis in conglomerates for regional stress reconstructions and (2) to advance reconstruction of the Western Carpathians structural development. Our results show that the Neogene fill of the Orava-Nowy Targ Intramontane Basin underwent CCW rotation of over 20 o . We infer that the rotation terminated after 8Ma and was related to dextral shift along NW-SE to NNW-SSE trending faults at the NE termination of the Mür-Žilina Fault Zone. Our results show that, fractured clasts can be good tool for regional tectonic reconstructions. The tool is especially useful when other tectonic tools are scarce or absent.Results of our palaeomagnetic study and fractured clasts analysis verify and supplement each others.In the studied case, palaeomagnetic results allow to distinguish between regional stress field rotation and rotation of the Orava-Nowy Targ Basin Neogene fill, whereas, results of fractured clast analysis help to constrain the age of rotation. Emile Argand Conference -EGU series, 12th Alpine Workshop, Montgenèvre / Briançon -French Hautes-Alpes, 13-19 September 2015. alpine-workshop-briancon-2015

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