Impact of storms on Pliocene benthic foraminiferal assemblages of southwestern Spain

Abstract

Lithostratigraphical and faunal analyses of five Pliocene sections located in the southwestern Guadalquivir Basin (S Spain) permit reveal three main facies, which represent shallow marine fairweather conditions (FA-1), storm events (FA-2) and littoral/fluvial environments (FA-3). The vertical disposition of these facies indicates a regressive sequence. The statistical study of foraminiferal populations revealed five infralittoral and circalittoral assemblages. Vertical and horizontal variations among these assemblages, the P/B ratio and four diversity indices, together with the mollusc distributions, suggest the presence of a shallow marine palaeoenvironment in this area in the Lower Pliocene, with an increasing depth towards the southwestern. The main effects from storm events on the foraminiferal faunas are a slightly decrease of individuals and species, and a marked drop in the P/B ratio. The post-storm conditions are characterized by: a) a higher number of individuals; b) a progressive increase in the P/B ratio and c) small increases in the remaining indices.