Jurassic climates as inferred from the sedimentary and fossil record

Abstract

A review is presented from the Jurassic terrestrial and marine fossil record, and the record of sediments and clay minerals, insofar as it bears on the two principal climatic parameters, temperature and precipitation. It is shown that there is a generally good agreement between palaeoclimatic data derived from fossils and rocks and the results of modelling experiments, provided a substantially higher atmospheric content of carbon dioxide is assumed for Jurassic times. The Jurassic world was relatively equable compared with the present day, but there were probably strong seasonal contrasts of temperature within the large continental areas, as well as some polar ice. Monsoonal effects were dominant on the continents and rainfall in low and mid latitudes was probably strongly seasonal, with arid conditions prevailing at low latitudes. Significant changes of temperature through the course of the period cannot be discerned, but some evidence tentatively favours a slight increase. A notable spread of aridity in southern Eurasia in the late Jurassic can be related to orographic effects. Some minor cyclicity in the sedimentary sequence may relate to orbital forcing.