Bioturbaciones de Tagelus plebeius (Lightfoot, 1786) (Mollusca: Bivalvia) en un ambiente estuárico holoceno (río Quequén Grande, Buenos Aires, Argentina)

Abstract

Elongated traces, showing a lower v-shape closed end have been identified in mid Holocene estuarine deposits exposed along the lower reach of the Quequén Grande River, Argentina (38°34'35" S and 58°42'45" W) associated with shells in life position of the infaunal bivalve Tagelus plebeius (Lightfoot). These traces, located in a stratigraphic level dated in cirea 6,900 years 14C B.P.,were originated by the burrowing activity of T. plebeius based upon the comparison of their morphological characteristics (width, general shape, colour) with those of T. plebeius and the traces resulting from its burrowing activity at present estuarine environments of the region. The high percentages of the estuarine gastropod Heleobia australis (d'Orbigny) found in the sedimentary filling of the traces come from the overlying strata, abundant in Heleobia australis remains. The traces are stratigraphically transgressive within a depth interval of up to 80 cm.