Orbital forcing of palynofacies in the Jurassic of France and the United Kingdom

Description/Abstract

Palynofacies analysis of marine Jurassic sedimentary successions in France and the United Kingdom demonstrates the pervasiveness of regular cycles in qualitative and quantitative aspects of the microscopic particulate organic content of the rocks, especially that part which is ignored during routine palynology. The cycles are attributed to precession, obliquity, and eccentricity forcing. Most of the palynofacies cycles are independent of lithology, whether it be cyclic, irregular, or uniform. Terrestrially derived organic particles record the effects of orbital cyclicity on land, which may be controlled by orbital cycles different from those controlling marine sediment deposition. The majority of studies on orbital cyclicity in the sedimentary record concentrate on cyclicity in lithology. This study demonstrates that sections lacking regular lithological cycles may still record evidence of orbital forcing of both the depositional environment and sediment source and transport.