134 9'h International Congress on the Jurassic System - Abstracts Parkinsoniids and garantianids (Late Bajocian Ammonoidea) as guide fossils and biostratigraphic indices GIULIO PAVIA1 * & SIXTO R. FERNANDEZ-LOPEZ 2 1Dipartimento di Scienze de/la Terra, Universita degli Studi di Torino, 10125 Torino, Italy; E-mail:
[email protected] 2Departamento Paleontologfa, Facultad Ciencias Geol6gicas, ea/le Jose Antonio Novais,2, Universidad Complutense de Madrid, 28040-Madrid, Spain; E-mail:
[email protected] Taphonomic, palaeobiological and appearances of innovative biota in several areas biochronological data are relevant in (then fossils in the stratigraphic record) may be interpreting time-space relationships of interpreted as synchronous events if they are the fossiliferous rock bodies, and in understanding effects of synchronous geographic dispersions the palaeoenvironmental changes taking from a common external source area. However, place on Earth' surface. It is assumed that the they are diachronous towards the source bed-by-bed order of succession shown by area. The appearances of innovative biota can fossils in the stratigraphic record represents be complementarily calibrated through the the chronological order of the producer taxa. synchroneity of the transgressive/regressive However, a particular feature of the fossil record changes analysed in sequence stratigraphy, too can condition the validity of the palaeontological (SANDOVAL et al. 2001). interpretations. In diverse cases it cannot be Since the latest decades of the past century,