OCORRÊNCIA DE OPHIOMORPHA NODOSA EM SEDIMENTOS PLEISTOCÊNICOS DA PLANÍCIE COSTEIRA DA PINHEIRA SANTA CATARINA BRASIL

Abstract (English)

The occurrence of Pleistocene (MIS) 5 marine ichnofossils in a locality of the Coastal Plain of Pinheira, State of Santa Catarina is described, and their value as indicators of the geological/stratigraphical evolution in this area is discussed. This sedimentary sequence indicates the transition among the subtidal zone, where the ichnofossils occur, to the supratidal zone, and finally to dunes. The ichnofossils can be seen in vertical view, between 0 and 4.5 m above the present sea level. The galleries are cylindrical structures with circular or oval transversal section, without ramifications. Their interior walls are smooth, and the exterior walls are composed of pellets made of clay and sand homogeneously dispersed, without a specific arrangement. This morphology is related to ichnospecies Ophiomorpha nodosa. The average density was 32.9 galleries/ m², ranging from 22 to 51 galleries/m². The highest density found could be related to time-averaging, or to a deeper subtidal environment. The vertical distribuition of Ophiomorpha and the absence of faciological variations in the deposits might indicate an aggradational stage between the trangressive and regressive phases.