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Provenance and Morphology of Extensive Oligocene-Miocene Deep-Water Fan Systems Sourced from Chiapas-Veracruz and Sierra Madre Oriental, Gulf of Mexico

Abstract

Here we present the results of an integrated seismic stratigraphic, detrital zircon U-Pb, and petrographic provenance study in the Gulf of Mexico that delineates a series of large-scale Oligocene to Miocene fan systems. We show extensive submarine fans, sourced from southern Mexican terranes, extended across a large area of the deep-water Gulf of Mexico basin into US waters. Evidence for significant deep-water clastic systems in the southern Gulf of Mexico have been documented previously, but here we demonstrate their extent over an area of ~3x105 km2 (comparable in areal extent to the Pleistocene Mississippi fan) and discuss the origins of such an accumulation of clastic sediment within a source-to-sink context. These fans are fed by several prominent large-scale (5-10 km wide) channel belts, mapped in 2D and 3D seismic data, which emerge from the southern sector within structurally active slopes and extend across a relatively low-relief basin floor. These primary conduits supply a series of compensating fan systems, comprising smaller-scale channels, which connect downdip to multiple lobe deposits (typically 10-50 km wide). DSDP cores from Site 91, located in the center of the basin, recovered coarse-grained Miocene sand which can be tied to the seismic expression of the sediment distribution pattern. These sands show detrital zircon U-Pb age signatures indicative of predominant sourcing from southern terranes, including Zongolica/Sierra Madre del Sur, Oaxacan and Acatlán complexes, Permian Chiapas basement, and recycled Jurassic Todos Santos Fm. Detrital zircon U-Pb ages from Oligocene and Miocene sands from deep-water wells in southern US waters also reveal anomalous Permian-aged zircons, strongly suggesting a link to the Chiapas massif. These new interpretations for Oligocene-Miocene fan systems extending north into US deep-water are consistent with our mapping of seismic stratigraphy and regional isochore trends. These results indicate a significant clastic input from southern Mexico initiating in the Upper Oligocene, peaking in the Middle Miocene and terminating by the end of the Miocene. Such a large volume of clastic detritus appears incongruous to the relatively limited scale of the proposed drainage areas. We evaluate the importance of other parameters controlling sediment flux and suggest that tectonics and climate may be significant factors in the volume of sediment released from these relatively small drainage areas.