The Orthaspidoceras uhlandi (Oppel) record and the maximum flooding in the Eastern Algarve during the Lower Kimmeridgian

Abstract

Detailed field work on Upper Jurassic outcrops in all of the eastern Algarve Basin, together with puntual observa­tions, leads to the improvement of our knowledge of the Lower Kimmeridgian in the area. The sediments belong to the Peral Formation, the upper part of which shows buildup remains dominated by sponges and algae, and to the lowermost Jordana Fm. The previously favourable environment for ammonites therefore decreased. The consistent ammonite record in the Divisum Zone ( Uhlandi Subzone), within or directly above reefal com­plexes or related sediments, is taken as proof of an episodic improvement of the environment for cephalopods. This event coincides well with the transgressive interval in the eustatic curves proposed by the Exxon Group, and especially with the maximum flooding of the epicontinental eastern Algarve Basin during the uppermost Lower Kim­meridgian.