The Guadiana Basin is an E-W intraplate Cenozoic basin located in SW of
the Iberian Peninsula, covering an area close to 6000 km2. NE-SW
Alpine faults divide the basin into two subbasins: the Vegas Altas (VA) to the
East, and the Vegas Bajas (VB) to the West. Sedimentary record consists of
<200 m thick of sediments, arranged in two main depositional sequences, DS1
and DS2. Petrographic analysis of sediment sandy-fraction combined with
geochemical analysis of <2 mm fraction permit to infer provenance and
factors controlling sediment composition. Petrographic analysis of
sandy-fraction reveals provenance from basin margins lithologies. In VA subbasin,
quartzolithic petrofacies characterized eastern subbasin infill related to the
erosion of Neoproterozoic and Palaeozoic metasediments. To the West
quartzofeldspathic petrofacies predominates, associated with the erosion of
coarse-grained plutonites and short distance transport of their products.
Intermediate petrofacies characterizes clastic deposits from the VB. Chemical
analysis of clastic deposits corroborates a main felsic origin of sediments
with a composition that fits well with the upper crust compositional norm and
with the Neoproterozoic Iberian Average Shale (NIBAS). In addition, minor
contributions from mafic sources can be identified in DS1 from VB, manifested
by anomalies in the content of Co, Ni, Cr, V and Sc. Different stages of weathering
(from intermediate to intense) can be deduced by the analysis of both,
sandy-fraction petrography and bulk sediment geochemistry. This fact is related
to the great hiatus at the base of the Cenozoicbasin infill. Transport-limited
denudation regimes can be inferred by the presence of high and intermediate
weathered and texturalyinmature sediments. In addition, trace element ratios
suggest local enrichment in dense minerals, attributable to recycling processes
from metasediments. Finally, the sedimentary record of the Guadiana Basin is
constituted by immature sediments formed by limited transsport processes of
very variable weathered products from recycled metasedimentary and first-order
sediments from granitoids.