Foraminifer communities and environmental change in marginal marine sequences (Pliocene, Tuscany, Italy)

摘要

Dominici, S., Conti, C. & Benvenuti, M. 2008: Foraminifer communities and environmental change in marginal marine sequences (Pliocene, Tuscany, Italy). Lethaia, vol. 41, pp. 447-460 Fossil abundance data on foraminifer communities were collected in marginal marine sediments of the Pliocene Valdelsa succession, in Tuscany, Italy. This succession is organized in a hierarchy of elementary and composite depositional sequences. Multivariate techniques allowed to analyse the dataset and reconstruct gradients in species distributions. Species-level data available on modern environmental distributions were used to reconstruct Pliocene environmental gradients and to infer absolute palaeodepths and palaeosalinities. Estimates were then compared with the sequence-stratigraphic interpretation to check for consistency. The high-resolution stratigraphic framework allowed us to test the stability of foraminifer communities against ecological variations related to high-frequency glacio-eustatic cycles. The results confirm that fossil distributions of foraminifer species can be used as a fine tool to detect environmental change and that multivariate techniques allow their interpretation in terms of absolute variations of controlling parameters. Salinity is the main contributor to the sum of depth-related factors that regulate foraminifer distributions in coastal facies. In the same setting, nutrient levels and the presence of a sea grass cover are responsible for secondary changes in shallow-water distributions. Below the wave base, however, depth-related parameters other than salinity explain the largest variations. This study indicates that foraminifer communities are random associations of species that respond individualistically to environmental change.