This paper analyzes the benthic foraminiferal assemblages present in two Upper Tortonian sections belonging
to the «Arcillas de Gibraleón» Formation (Guadalquivir Basin) containing a characteristic glauconitic level.
The basal samples of this horizon show both shallow-water and epibathyal taxa, a mixture also found in
ostracods that may characterize the transition toward deeper conditions. In the upper samples, deepneritic
and epibathyal species are dominant, indicating a moderate-deep environment (150-300 m) in
which was deposited most of the glauconitic horizon