17 - Sedimentary facies analysis in palaeoclimatic reconstructions. Examples from the Upper Miocene–Pliocene successions of south-central Tuscany (Italy)

Summary

Introduction

One of the purposes of the workshop on ‘Climatic and environmental changes in the Neogene of Europe’, was to assemble different points of view on problems which by their nature need a multidisciplinary approach. Climatic and environmental changes can be detected in the geologic record by palaeontologists, sedimentologists and geochemists, through integration of their efforts. The goal of this paper is to show how sedimentology can contribute to such multidisciplinary studies. Facies analysis has acquired a great importance in the detailed study of sedimentary deposits. A facies is a rock or sediment unit distinguishable from others on the basis of its specific aspect (from Latin facies) including lithologic, sedimentologic, and biologic features. A sedimentary facies records the physical, chemical or biological processes operating during sedimentation. Facies associations and sequences (the spatial arrangement of facies) provide information on the depositional environments and on their dynamics. Selected examples from Upper Miocene–Pliocene continental and shallow marine deposits filling some post-collisional basins in southern and central Tuscany (central Italy, Fig. 17.1a), will show in the following paragraphs, the potentialities and limits of facies analysis as an integrative tool for palaeoclimatic reconstructions.

General setting

The sedimentary basins we deal with in this paper are located in central and southern Tuscany (central Italy), on the western margin of the Northern Apennines, a thrust and fold chain whose formation started in the Late Cretaceous. In the Middle (Carmignani et al., 1994) or Late Miocene the western side of the chain was affected by crustal extension, possibly alternated with (Bernini et al. (1990) or subordined to (Boccaletti et al., 1991, 1995) compression.