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The interaction of eustacy and tectonism from provenance studies of the Eocene Hecho Group Turbidite Complex (South-Central Pyrenees, Spain) |
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| Authors: | DANIELA Fontana GIAN GASPARE Zuffa EDUARDO Garzanti‡ |
| Institution: | *Istituto di Geologia, Universita' di Modena, Corso V. Emanuele II, 59, 41100 Modena, Italy;**Dipartimento di Scienze Geologiche, Universitádi Bologna, Via Zamboni, 67, 40127 Bologna, Italy;‡Dipartimento di Scienze delta Terra, Universita' di Milano, Via Mangiagalli, 34, 20133 Milano, Italy |
| Abstract: | Abstract Using a detailed petrographical procedure conceived for arenites rich in carbonate clasts, the influence of tectonism and eustacy on silicate/carbonate cycles of the Eocene Hecho Turbidite Complex has been tested, and the palaeogeography of the source/basin system outlined. Both extrabasinal and intrabasinal sources of sediments were active during basin filling. The extrabasinal source terrains, located in the southern sector of the basin, were made of the Pyrenean crystalline basement (granites, gneisses and phyllites) overlain mainly by carbonate rocks (Cretaceous limestones and dolostones, minor chert and siltstones). The intrabasinal sources, represented by foramol shelf carbonate factories, provided penecontemporaneous carbonate bioclasts, intraclasts and peloidal grains. Foreland thrusting in the South-Central Pyrenees has acted as the major control on the composition and architecture of the Hecho Turbidite Complex. Strong uplift of old silicate and carbonate source terrains during southward thrust propagation was responsible for erosion, swamping and/or reduction of shelfal areas, and gave rise to siliciclastic and carbonate basinal sequences (silicate arenites and calclithites) during lowstand stages. Conversely, hybrid arenites (mixture of extrabasinal and intrabasinal grains) originated from resedimentation of marginal shelf sediments produced in carbonate factories active during the initial phase of sea-level rise. Hybrid arenites with minor intrabasinal content also formed during one stage of relative sea-level fall from the erosion of previously accumulated highstand complexes. During resedimentation processes, hybrid sands underwent marked hydraulic selection documented by deposits depleted in carbonate grains in the channel area, and by thin-bedded turbidites rich in platy-skeletal fragments, low-density peloids and void-rich bioclasts down-basin. |
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