Le néogène et le pléistocène inférieur duranciens

As regards to the geography, the present study covers the Digne-Valensole basin, the lowest part of the Durance river and Crau country. Stratigraphic study of the neogen and durancian Lower pleistocen series, lateral dependance of rhodanian neogen series, rest on about forty classical or unpublished sections wich put in evidence one miocen cycle and one plio-villafranchian cycLe . Each one achieves its evolution by the installation of thick continental gravelous spreading till now clusted in a only complex called " Poudingues de Valensole ". Are examinated successively : - the basin substratum, - the marine miocen series , - the continental miocen series, called " Sables de Vinon ", - the lacustrian upper-tortonian serles, - Digne-Valensole ' s complex : in spite of the lentiform disposition of the deposits , of their interpenetrating structure and of the general absence of fauna, five stratigraphic formations become obvious, from upper-tortonian series to Iower-villafranchian series included, - the upper and middle pleistocen formations. The petrographic analysis of the Digne- Valensole 's complex pebbles has permitted to define eight rocks groups and has revealed the diversity of the paleo-durancian upper-slide basin, from the upper-tortonian series to the villafranchian series : aIl the strata from Paleozoïc to Meridional and Provence Alps lacustrian upper-miocen series are present here. A statistic study of the differents types of pebbles was effected from 119 populations. For each of them 1.000 individual samples are inventorized, a diagram was drawn. So is deducted the origin of the materials and the morphological evolution of the upper-area during the successive sequences of his edification and of his rasing . For the Alps, only the subalpine sedimentary mantle had a share in the infil ling ; the outside cristallin rocks body ( Massifs cristallins externes) fed the Durance river only at the middle pleistocen period. The collective disposition of pebbles, investigated from 392 stations permit to precise the direction of discharge of the paleo- streams and so to reconstitute the initial river system , wich difer with the actual system (Pl. XX to XXV). Materials provide exclusively from the North , from the East and from the South. The study of the clayed materiels has shown : Montmorillonite (alpine inheritance) in the marine miocen series, in the conglomeratic formation of Digne-Valensole's complex and in Puimoisson' s formation , Chlorite and illite inherited from Maures in the continental Miocen and Moustiers ' s red formation. The study of Digne-Valensole's complex permit to reconstitute the successive orogenesis sequences in the Meridional Subalpine Mountain Range during the neogen and the old pleistocen periods and their incidences on the provençal area.