MIOCENE BARNACLE ASSEMBLAGES FROM SOUTHERN SPAIN AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE

The Tabernas Basin in southeast Spain is a Neogene intermontane basin which filled with subaerial and submarine fan conglomerates grading in to turbidite sandstones towards the basin centre. The basin history in volved the development of Seravallian-Tortonian subaerial fans which c oalesced southwards from the basin margin. Increasing water depth in t he Tortonian led to a submarine development of these fans. The coarse fan conglomerates are colonized almost solely by barnacles of the spec ies Megabalanus tintinnabulum, known from Miocene-Recent deposits. The barnacles occur in seven preservational-state assemblages, which prov ide a record of the colonization of stabilized mass-flow conglomerates and of subsequent reworking episodes. M. tintinnabulum is known from intertidal environments today. In situ clusters developed on the fan c onglomerates record the transition of the fans from subaerial to subma rine environments. Mass-flow deposits rich in barnacle shell debris ar e representative of basin-wards reworking of intertidal clusters and i llustrate relative increase in water depth. A further shallowing episo de is identifiable by the recolonization of mass flows by in situ barn acle clusters. This case history is demonstrative of the utility of so me barnacles in determining basin history with respect to minor sea le vel fluctuations.