Unidades litoestratigráficas del Cretácico de Ibiza (Islas Baleares, España)

Abstract

Seven new lithostratigraphic units are defined for the Cretaceous of the Ibiza Island, since there were no previously defined units for this System in this area: Punta Jondal Fm (Tithonian-Valanginian); Es Cubells Fm (Tithonian-Cenomanian); Port Sant Miquel Fm (Aptian), that includes three local members, Torre des Molar Mb (Lower Aptian, Bedoulian), Penyal de s`Águila Mb (Gargasian) and Cala d`en Sardina Mb (Upper Aptian, Clasayesian); and Llentrisca Fm (Cenomanian-Maastrichtian). Two evolutionary stages can be clearly recognised in the Cretaceous stratigraphic record. Firstly, early Cretaceous sediments show significant lateral changes in lithofacies as a consequence of the diversification of shelf-basin sedimentary environments. These changes have a NW-SE trend and started in the Tithonian, when the sedimentary uniformity of Triassic and Jurassic successions ended; they were previously described by RANGHEARD (1969, 1971) who defined the unformal Aubarca, San José and Ibiza series. Thus, the Ibiza serie is composed of a thick and rhythmic alternation of marls and marly limestones (Es Cubells Fm) of open platform environments (Tithonian-Cenomanian). Northwestwards, the appearence of a first carbonate lithosome (Punta Jondal Fm) deposited in inner platform environments was used to define the San José serie. Similarly, the Aubarca serie was established by the appearance of reefal limestones at the Aptian (Port Sant Miquel Fm). Secondly, late Cretaceous sediments reflects a greater uniformity of the depositional environments along the basin, being composed of well-bedded limestones (Llentrisca Fm) of shallow platform environments. Five long-term depositional episodes with complex stratal stacking patterns (retrogradational, aggradational, progradational) can be recognised. The first episode is represented by the limestones of the Punta Jondal Fm northwestwards and by the lowermost part of Es Cubells Fm southeastwards; it shows a retrogradational trend regarding the underlying jurassic succession. The second episode is composed by the lower-middle part of Es Cubells Fm and Torre des Molar Mb, the lower member of Port Sant Miquel Fm, reflecting the progradation of inner platform reefal carbonate facies on the open platform marly facies of Es Cubells Fm. The third episode is composed of Penyal de s`Águila Mb and Cala d`en Sardina Mb (Port Sant Miquel Fm) northwestwards, and by the middle-upper part of Es Cubells Fm southeastwards; it represents a symmetrical retrogradational-progradational episode. The fourth episode is composed of the uppermost part of Es Cubells Fm and the lowermost part of Llentrisca Fm, and shows again a retrogradational-progradational geometry. Finally, the fifth episode is composed by the rest of Llentrisca Fm and shows an apparently aggradational trend as evidenced by the presence of the inner carbonate platform settings throughout the rest of the Upper Cretaceous.