Tectono-stratigraphic evolution of a Mesozoic Graben Border System: the Chachil depocentre, southern Neuquén Basin, Argentina.

FRANZESE, J.R.; VEIGA, G.D.; SCHWARZ, E.; GÓMEZ-PÉREZ, I.

JOURNAL OF THE GEOLOGICAL SOCIETY

Geological Society Publishing House

Año: 2006 vol. 163 p. 707 - 721

0016-7649

The Chachil depocentre is one of a number of early Mesozoic extensional basins that form theearlydepocentresofthesouthernNeuque´nBasininArgentina.The synrift volcanic fill iscomposedofandesites,rhyolitesandvolcaniclasticdeposits.Coarse-grained,non-marinefacies dominate the sedimentary infill,mainlyintheformofsedimentgravity flowdeposits.Stream flowdepositsandminornon-marine carbonatesarealsolocallypresent.Theevolutionofthegrabenbordersystemwasmainlycontrolledbysubsidencealongthemainboundaryfault(theChihuidoBayofaultsystem)andrecurrentvolcanicactivity.Markedchangesinthethicknessofthesynriftmegasequenceindicatethatepisodicnormalfaultinginthehangingwallwasalsoimportant.Theintegrationofstructural,magmaticandsedimentarydatafromthestudyareahasledtothede?nitionofthreestagesintheevolutionofthesynriftsuccession.Theearlyriftstageisdefinedbytheinterplaybetweenbimodalvolcanismandgravity-drivensedimentation.Themid-riftstageismarkedbythetransitiontoacidicmagmatism(rhyoliticandpyroclasticflows),alsoassociatedwithcoarse-grainednon-marinedeposition.Thelate-riftstageisdominatedbyfine-grainedturbiditesandpyroclasticfallsrelatedtothe?rstmarinesedimentationintheNeuque´nBasin.