COASTAL PALEOENVIRONMENT: A LOWER DEVONIAN (EMSIAN) LAND-SEA TRANSITION SOUTH OF THE OLD RED CONTINENT (MOSEL SYNCLINE, RHEINISCHES SCHIEFERGEBIRGE, GERMANY)

Results of an interdisciplinary study on sedimentology, paleontology, facies, and paleogeography of a Lower Devonian section (Nellenköpfchen Formation, uppermost Lower Emsian) near Alken (Mosel Valley) are presented. The rocks mainly consist of stratified sandstones and sandy shales. Previous interpretations considered the sequence to represent a range of environments from terrestrial over deltaic to shallow marine.

In the section two distinct, fossiliferous units contain abundant terrestrial plant remains and a diverse fauna. Physical sedimentary structures prevail throughout, whereas bioturbation is mostly restricted to the fossiliferous units. Erosional surfaces mainly separate the beds. Aside from ripple cross-stratification and parallel bedding, longitudinal cross-bedding is most common. Channel-fills are less frequent. Scour-and-fill structures exhibit marked disconformities of irregular shape on a smaller scale. Mud pebble layers at the base of laterally prograding cross-bedded layers, scour-and-fill structures, and drainage rills characterize the upper part of the section. More sporadically, desiccation cracks, wind-induced striations, and water-level marks occur.

The sedimentary structures and the paleontological information indicate a marine to brackish environment with frequent emergence in an intertidal setting along the coastal region (including lagoons and estuaries) of a presumed Hunsrück Island/Archipelago. Terrestrial plant remains indicate a position at the land/sea interface characterized by a complex configuration of different environments. Thick packages of plant material may have been derived during meteorological events such as hurricanes.