Sediment dispersal and palaeohydraulics of Oligocene rivers in the eastern Ebro Basin |
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| Authors: | PHILIP ALLEN MARIA MANGE-RAJETZKY |
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| Institution: | Geologisches Institut, Universität Bern, Sahlistrasse 6, 3012 Bern, Switzerland |
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| Abstract: | Mapping of heavy mineral associations and diagnostic accessories in Oligocene sediments of the eastern Ebro Basin has revealed two major provinces and several sub-provinces. The Pyrenean Province is characterized by an apatite-tourmaline-garnet association with diagnostic staurolite in the west (western Pyrenean Sub-Province) and micaceous composite grains plus chloritoid in the east (eastern Pyrenean Sub-Province). The Catalanides Province is characterized by an ultrastable angular brown tourmaline-staurolite association with kyanite in the south-west (Montsant Sub-Province), faceted garnets and rounded tourmalines in an intermediate position (St Miquel del Montclar Sub-Province) and in the north-east rounded and green tourmalines admixed with clinopyroxene, apatite and micas derived from the Pyrenees (Montserrat Sub-Province). Palaeodischarges have been estimated from 30 channels distributed throughout both major provinces. A gradual decrease in river discharge through Oligocene times is indicated for the rivers of Catalanides parentage, although the discharges of high-sinuosity streams alone remain uniform. This decrease through time of Catalanides drainage competitiveness is reflected in the greater areal extent of the Pyrenean petrological province together with a progressive displacement south or south-eastwards of basinal lacustrine facies. The increasing dominance of Pyrenean drainage during the Oligocene may be due to more prolonged tectonic activity in the Pyrenees compared to the more quiescent Catalanides. |
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