Constraining the source terranes of Alpine siliciclastic flysch sequences is crucial for building a clearer picture of the palaeogeography and geodynamic evolution of the Western Tethys in the framework of impending continental collision. This paper presents an integrated study that involves palaeocurrent dispersal analysis, sandstone petrography and detrital zircon geochronology of the Upper Cretaceous-Paleocene Monte Bignone Sandstones, a siliciclastic turbidite system deposited during the pre-collisional evolution of the Ligurian Alps. Palaeocurrent analysis illustrates an overall eastward transport of the proximal sediments in the present configuration. Considering the ca. 45 degrees-50 degrees counter-clockwise rotation of the Tertiary Piedmont Basin and of the Corsica-Sardinia block in the late Paleogene, this indicates the derivation of the sediments from the northern margin of the Piedmont-Ligurian Ocean. Sandstone petrography records a stratigraphic evolution from quartzose sandstones towards lithic and then to lithic sub-arkosic composition. This trend is interpreted to reflect the gradual unroofing of the provenance terrane. The lithotypes of the recycled sedimentary rock fragments and the up-section increase in dolostone and carbonate clast proportions suggest the erosion of the sedimentary cover of the southern European palaeo-margin. New geochronological data (U-Pb detrital zircon ages) correspond to the pre-Alpine stages of crustal growth recorded in the Variscan Maures-Tanneron Massif, and therewith confirm the derivation of the sediments from the passive palaeo-European margin. This conclusion highlights the importance of the lower plate in providing the source of coarse-clastic deep-water successions during pre-collisional convergent steps. Results from this multi-proxy provenance analysis contribute to better defining the detrital signatures associated to the continental micro-fragments that constituted the palaeo-European plate as it supplied deep-sea siliciclastic sediments into the Piedmont-Ligurian Ocean prior to continental collision.
Towards a Southern European Tethyan Palaeomargin provenance signature: sandstone detrital modes and detrital zircon U-Pb age distribution of the Upper Cretaceous-Paleocene Monte Bignone Sandstones (Ligurian Alps, NW Italy)
Langone Antonio;
2020
Abstract
Constraining the source terranes of Alpine siliciclastic flysch sequences is crucial for building a clearer picture of the palaeogeography and geodynamic evolution of the Western Tethys in the framework of impending continental collision. This paper presents an integrated study that involves palaeocurrent dispersal analysis, sandstone petrography and detrital zircon geochronology of the Upper Cretaceous-Paleocene Monte Bignone Sandstones, a siliciclastic turbidite system deposited during the pre-collisional evolution of the Ligurian Alps. Palaeocurrent analysis illustrates an overall eastward transport of the proximal sediments in the present configuration. Considering the ca. 45 degrees-50 degrees counter-clockwise rotation of the Tertiary Piedmont Basin and of the Corsica-Sardinia block in the late Paleogene, this indicates the derivation of the sediments from the northern margin of the Piedmont-Ligurian Ocean. Sandstone petrography records a stratigraphic evolution from quartzose sandstones towards lithic and then to lithic sub-arkosic composition. This trend is interpreted to reflect the gradual unroofing of the provenance terrane. The lithotypes of the recycled sedimentary rock fragments and the up-section increase in dolostone and carbonate clast proportions suggest the erosion of the sedimentary cover of the southern European palaeo-margin. New geochronological data (U-Pb detrital zircon ages) correspond to the pre-Alpine stages of crustal growth recorded in the Variscan Maures-Tanneron Massif, and therewith confirm the derivation of the sediments from the passive palaeo-European margin. This conclusion highlights the importance of the lower plate in providing the source of coarse-clastic deep-water successions during pre-collisional convergent steps. Results from this multi-proxy provenance analysis contribute to better defining the detrital signatures associated to the continental micro-fragments that constituted the palaeo-European plate as it supplied deep-sea siliciclastic sediments into the Piedmont-Ligurian Ocean prior to continental collision.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
