Facies successions in the pre-evaporitic Late Miocene of the Lorca Basin, SE Spain

Abstract

Abstract Pre-evaporitic uppermost Tortonian to Messinian carbonate–siliciclastic deposits have been studied in the western part of the Lorca Basin. Individual lithofacies, facies associations as well as facies successions and stratal architecture indicate a gravel-rich fluvial-dominated (Gilbert-type) delta environment. During periods of decreasing terrigenous supply carbonate sedimentation predominated including formation of patch reefs and fringing reefs. The observed progradational stacking pattern of facies successions is attributed to a `3rd-order' eustatic highstand that pre-dates the Messinian lowstand evaporites of the well known `salinity crisis'. Five facies successions have been recognized. Each succession is composed of three facies associations that are: mixed carbonate–siliciclastic (mcs), carbonate-dominated (cd) and siliciclastic-dominated (sd). They show retrogradation–aggradation–progradation architecture and represent `4th-order' transgressive–regressive cycles. The five successions can be correlated through the whole basin and are interpreted as a useful tool for basinwide sequence stratigraphic correlation. If, in addition, other recently published data from SE Spain are considered it may turn out that future correlations between different Neogene basins at this cycle scale (`4th-order') will be possible. Higher-frequency successions or cycles at a bed or bedset scale (`5th- or higher order') are noticeable but are clearly related to local depositional processes (facies dynamics). They do not have any significance for a basinwide sequence stratigraphic correlation.