Late Miocene Cymodocea seagrass in the Guadalquivir Basin (southern Spain)

Abstract

Despite the abundance of seagrass-related deposits in the geological record, seagrass macrofossils are scattered in time and space, due to the low preservation potential of marine angiosperms. Fossil seagrass impressions, mainly rhizomes occur in Messinian (late Miocene) marl beds intercalated in cross-bedded bioclastic limestones in the Guadalquivir Basin near Alcalá de Guadaíra in southern Spain. Vegetative characters indicate that most remains can be attributed to Cymodocea cf. nodosa, to which also probably belong a few molds of fruits. Two other fossil fragments can only be assigned to Alismatales indet. The plants lived in sheltered ephemeral areas among shallow-water submarine dunes, in which deposition of fine-grained sediment favored their fossilization. During the late Miocene the Guadalquivir Basin was open to the Atlantic Ocean and, therefore, these fossil occurrences lie within the modern biogeographic distribution of C. nodosa, the only species of the genus out of the Indo-West Pacific region. At the moment, it is the only record of seagrass fossils in the Miocene of Europe.