%0 Conference Proceedings %T Characterization of syn-sedimentary volcanism in volcaniclastic series using coupled sedimentological and geochronological (U-Pb/zircon) analyses %+ Géosciences Rennes (GR) %A Rossignol, Camille %A Poujol, Marc %A Bourquin, Sylvie %A Dabard, Marie-Pierre %A Hallot, Erwan %A Nalpas, Thierry %< avec comité de lecture %( Geophysical Research Abstracts %B European Geoscience Union General Assembly 2015 %C Vienne, Austria %3 17 %P EGU2015-11986 %8 2015-04-12 %D 2015 %Z Sciences of the Universe [physics]/Earth SciencesConference papers %X Volcaniclastic sediments, often under-studied, constitute an important part of the global sedimentary record, bothin marine and continental environments. These sediments are of particular importance in order to constrain the ageof sedimentation, particularly in series where interbedded lava flow are absent. Volcaniclastics sediments are alsoused in order to constrain the duration of the volcanic activity and to link volcanism with a specific geodynamiccontext. To demonstrate that volcanism and sedimentation were contemporaneous in a given basin, it is crucial todetermine to which extent volcaniclasts present in the volcaniclastic sediments have been reworked. However, thisdetermination is notoriously difficult.As a case study, we characterized the Triassic volcaniclastic series from the Luang Prabang Basin, Laos,using coupled sedimentological and geochronological analyses. Sedimentological and petrographical analysesshow a wild range of depositional environments (alluvial fan, braided river and alluvial plain) and evidence forreworking of the volcaniclastics in each of the corresponding deposits. U-Pb geochronology conducted on zircongrains extracted from the volcaniclastic samples of known stratigraphic position indicates that the maximumdepositional ages get younger together with the sedimentary succession. This good correlation between absoluteages and stratigraphy demonstrates that, despite evidences of reworking, the volcaniclasts were produced, atleast to some extent, contemporaneously with sedimentation. Then, in this specific example, the uncertaintiesobtained from the U-Pb ages can be used to indicate maximum ‘reworking time scales’, the reworking timescale being defined as the difference between the age of volcaniclast production and the depositional age of itshost strata. Short maximal reworking time scales, of ca. 1 Ma, one order of magnitude smaller than the totalduration of the sedimentary record reveal that volcanism and sedimentation were contemporaneous. The use ofcoupled sedimentological and geochronological analyses may thus allow to determine the duration of volcanicactivity even in the absence of volcanic deposits. Constraining the reworking time scales is useful to describevolcaniclastics deposits in which the volcaniclasts were reworked. %G English %L insu-01118594 %U https://insu.hal.science/insu-01118594 %~ INSU %~ UNIV-RENNES1 %~ UR2-HB %~ CNRS %~ GR %~ OSUR %~ UR1-HAL %~ UR1-SDLM %~ UR1-SDLMJONCH %~ GR-PPDB %~ GR-3T %~ UNIV-RENNES2 %~ TEST-UNIV-RENNES %~ TEST-UR-CSS %~ UNIV-RENNES %~ INRAE %~ UR1-ENV %~ GR-P %~ GR-FRODO %~ GR-CHRONOS