Importance of predecessor basin history on sedimentary fill of a retroarc foreland basin: provenance analysis of the Cretaceous Magallanes basin, Chile (50-52°S)
- ISSN: 0950091X
- DOI: 10.1111/j.1365-2117.2009.00443.x
Abstract
An integrated provenance analysis of theUpperCretaceous Magallanes retroarc foreland basin of southernChile (501300 521S) provides newconstraints on source area evolution, regional patterns of sediment dispersal and depositional age.Over 450 newsingle-grain detrital-zirconU-Pb ages,which are integratedwith sandstone petrographic andmudstone geochemical data, provide a comprehensive detrital record of the northernMagallanes foreland basin-lling succession (44000- m-thick). Prominent peaks in detrital-zircon age distribution among the Punta Barrosa, CerroToro, TresPasos andDoroteaFormations indicate that the incorporation and exhumation ofUpper Jurassic igneous rocks (ca.147 155Ma) into the Andean fold-thrust beltwas established in the Santonian (ca. 85Ma) andwas a signicant source of detritus to the basin by theMaastrichtian (ca.70Ma).Sandstone compositional trends indicate an increase in volcanic and volcaniclastic grains upward through the basin ll corroborating the interpretation of an unroong sequence.Detrital-zircon ages indicate that the Magallanes foredeep received young arc-derived detritus throughout its ca. 20m.y. lling history, constraining the timing of basin- lling phases previously based only on biostratigraphy. Additionally, spatial patterns of detrital-zircon ages in theTresPasos andDoroteaFormations support interpretations that they are geneticallylinked depositional systems, thus demonstrating the utility of provenance indicators for evaluating stratigraphic relationships of diachronous lithostratigraphic units.This integrated provenance dataset highlights how the sedimentary ll of the Magallanes basin is unique among other retroarc foreland basins and fromthewell-studiedAndean foreland basins farther north,which is attributed to nature of the predecessor rift and backarc basin.
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