Tempestitic shell beds formed by a new serpulid polychaete from the Bajocian (Middle Jurassic) of the Central High Atlas (Morocco)

摘要: Serpulid-dominated shell beds from the Lower Bajocian (Middle Jurassic) of Central High Atlas (Morocco) are primarily formed by quadrangular tubes serpulid polychaete Nogrobs moroccensis sp. nov. The transverse tube ornament consisting predominately wrinkles, lack narrow spirals and shortness or absence attached posterior portion represent diagnostic features this new species. Tubes co-occur with gastropods oyster–crinoidal debris. We suggest that these serpulids were free-lying in their adult stage benthic meadows on soft-bottom habitats. They frequently show parallel alignment plane views both graded non-graded, few-cm-thick beds, corresponding to distal tempestites deposited close below storm wave base an outer-ramp environment. excellent preservation implies short residence time seafloor, compositional mixing other communities restriction habitats indicate they parautochthonous assemblages. Analyses orientation bottom bedding planes revealed weak unidirectional arrangement tubes, whereas top strong significantly different relative planes. This change could a shift predominantly current component combined flow (with uneven seafloor surface adhesion skeletal grains muddy substrate) significant oscillatory waning storm, as also suggested bidirectional gastropods.