Factors Controlling Oncoid Distribution in the Inner Areas of a Late Kimmeridgian Carbonate Ramp (Northeast Spain)

Abstract

The factors controlling the oncoid distribution in the interior areas of a latest Kimmeridgian shallow carbonate ramp were examined based on a detailed sedimentological and petrographic analysis of the upper sequence of the Higueruelas Formation (Iberian Basin, Northeast Spain). Four types of oncoids are defined: small micrite-dominated type I and II oncoids are generally found in low proportion in all sub-environments (from backshoal/washover, lagoon to intertidal). Large Bacinella-dominated type III and IV oncoids predominate in low-energy lagoonal areas. Variable energy water, oligotrophic conditions and probably low sedimentation rates controlled oncoid growth and distribution, thus highlighting their potential as palaeo-environmental proxies.