Upper Jurassic (Portlandian) sedimentology and palynofacies of Cabo Espichel, Portugal

Abstract

Upper Jurassic (Portlandian) strata on the southeastern margin of the Lusitanian Basin at Praia-do Cavalo, near Cabo Espichel, Portugal contain mixed carbonate and clastic sediments. From this section ten facies were identified to produce a model of Upper Jurassic shelf development on a passive Atlantic-type margin. -- The model consists of carbonate shelf and clastic deltaio sediments linked by erosional and non-erosional contacts. The shallow marginal marine carbonate sequence consists of intertidal and low energy and high energy subtidal environments. The clastic sequence consists of interdistributary bay fill, crevasse splay, levee, channel, distributary mouth bar and delta front environments. Non-erosional boundaries occur where levees, crevasse splays and bay fill prograde over shallow subtidal nodular limestones and calcareous shales. Erosional boundaries occur where distributary channels soour through distributary mouth bars and prodelta strata to sharply - rest upon lithified massive subtidal limestones. -- The miospore assemblage consists of 49 terrestrial and 4 marine species in samples dominated by Corollina (Classopollis), Exesipollenites and Spherioollenites. Three palynofacies are identified; the C. simplex palynofacies is associated with siliciclastic lithologies; C. itunensis palynofacies is restricted to the carbonates and; the marine palynomorph facies is characteristic of some carbonates and delta front siliciclastics. -- The C. simplex - sediment association indicates that this pollen was derived from a plant which occupied an inland marsh or levee environment. The C. itunensis - sediment association implies a plant living on or near a marginal marine carbonate coast resembling a “mangrove” or saltmarsh environment.