Surface sediment distribution, sources and transport pathways in the Gulf of San Jorge, Central Patagonia (Argentina)

GUILLAUME ST-ONGE; MONICA GIL; PIERRE-ARNAUD DESIAGE; AUGUSTO CÉSAR CRESPI ABRIL; MIGUEL J. HALLER; JEAN-CARLOS MONTERO-SERRANO; ERICA GIARRATANO

OCEANOGRAPHY

OCEANOGRAPHY SOC

Año: 2018 vol. 31 p. 23 - 31

1042-8275

The Gulf of San Jorge (GSJ) is a semicircular basin, approximately 160 kmlong and 250 km wide, located in the central part of Patagonia between 45°S and 47°S,lacking any present-day major perennial tributaries. The grain size and bulk and claymineralogical compositions as well as major and minor elements of 75 surface sedimentsamples from the GSJ and the adjacent continental shelf were investigated todefine the spatial distribution, transport pathways, and potential sources of terrigenousmaterial. To better constrain the origins of GSJ sediments, analyses were alsoperformed on 14 terrestrial, riverine, and marine samples from potential source areasaround the gulf and Patagonia. The mineral assemblage of surface sediments in thegulf, dominated by plagioclase, quartz, and clays, is a function of the primary continentalvolcanic geology of Patagonia. The significant concentration of volcaniclastic particlesindicated by mineralogical signatures and scanning electron microscope images ofsediments suggests a substantial contribution from rhyolitic volcanism to the modernsedimentation in the gulf. High amounts of smectite are carried into the GSJ by dusttransport, whereas inputs of chlorite and illite seem to be associated with continentalshelf current transport from southern Patagonia. Finally, our results suggest that 50%of the surface sediment in the GSJ is derived from external/oceanic inputs, 40% frominner gulf shores (i.e., erosion and runoff), and 10% from dust (i.e., aeolian transport).