© Blackwell Science Ltd, Geology Today, Vol. 17, No. 4, July–August 2001 148 David A. T. Harper Geological Museum, Copenhagen, Denmark Fossils explained 36 Fossils in mountain belts tions within zones of structural complexity. Fossil data have proved decisive in developing models for the age and way-up of deformed strata, their origins and original environmental settings, the timing of deformation and rates and direction of nappe transla- tion. Although biostratigraphy remains the main fo- cus of palaeontological activity in mountain belts, palaeogeography and terrane analysis, environmen- tal analysis particularly of shelf-margin successions, recognition of sea-level changes and palaeothermom- etry, together with strain analysis, have relied heav- ily on data derived from fossils. The importance of fossils in the study of mountain belts had already been established by the Pythago- rean School; in its view, as elucidated by Lyell in the 1830s, clearly the ‘sea had been changed into land’ and now ‘marine shells lie far distant from the deep’. The Danish scientist and philosopher Steno (Nicolaus Fig. 1. The deformed trilobite Damesops sheridanorum, from near Kuru, Zanskar Valley, India, latest Middle Cambrian in age (×2). (Photograph courtesy of Nigel C. Hughes, University of California, Riverside.) Lemoine, M., Barféty, J.-C., Cirio, R. & Tricart, P. 1994. Montagnes du Briançonnais – Promenades et Randonnées – Initiation À la Géologie. Éditions du BRGM, Orléans, 136pp. Lemoine, M., Ciro, R., Pellet, G. & Keck, R. 1995. Le Massif du Chenaillet – Montgenèvre – (Alpes Franco- Italiennes). Centre Briançon de Géologie Alpine, Briançon, 96pp. Lemoine, M. & Tricart, P. 1988. Queyras: un océan il y a 150 millions d’années – initiation à la géologie sur les sentiers du Queyras. Éditions du BRGM, Orléans, 112pp. Mason, R. 1985. Ophiolites, Geology Today, v.1, pp.136–140. Pollino, R. 1984. Les Series Oceaniques du Haut Val de Suse (Alpes Cottiennes). Analyse des Couvertures Sedimentaires, Ofioliti, v.9, pp.547– 554. Read, H.H. 1957. The Granite Controversy. Thomas Murby, London. Vissers, R., Drury, M. & Dijstra, A. 1997. Rifting, breakup and oceanization in the western Neotethys: a perspective from ophiolitic upper- mantle fragments in the Alps and Hellenides, Quaderni di Geodinamica Alpina e Quaternia, v.4, pp.139–140. Most palaeontologists prefer to collect, describe and analyse fossils from the stable platform successions. Here, fossils are usually well preserved and undistorted, relatively common and accessible. Tradi- tionally, these faunas and floras have formed the basis for detailed taxonomic studies and the develop- ment of biostratigraphical correlation schemes. More recently, these biotas have been developed in palaeo- ecological studies, involving the analysis of func- tional morphology and palaeocommunity structures together with isotopic studies of their bones and shells. In many respects, however, fossils from moun- tains belts are much more interesting. Although often deformed, relatively rare and inaccessible, fossils have driven fundamental advances in our understanding of the origins and structure of mountain chains to- gether with the elucidation of orogenic processes. Deformed fossils (Fig. 1) hold a considerable amount of information about the age and the environmental and geographical settings of the enclosing sedimen- tary rocks and also provide valuable data on the finite strain recorded in the rock. Understanding of the str- atigraphy and structure of the European mountain belts is based to a significant extent on the use of fossil data. Fossils have helped recognize tectonic events by constraining deformed rocks and associated unconformities, bracketing magmatic phases within fossiliferous sequences and establishing facing direc- GUIDE