Análisis tafonómico de moluscos por debajo de la interfase agua-sedimento en la laguna Nahuel Rucá (provincia de Buenos Aires, Argentina)

CRISTINI, PAULA ANDREA; DE FRANCESCO, CLAUDIO GERMÁN

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2012 vol. 49 p. 594 - 605

0002-7014

The preservation of mollusk remains below the sediment-water interface in Nahuel Rucá lake (37°37’S, 57°25’W) was analyzed in order to determine the degree of taphonomic alteration and to estimate the vertical extension of the taphonomically active zone (TAZ). To do that, a description of the preservation patterns observed in five cores extracted from the littoral zone was performed, and the effect of depth and presence of periostracum on shell dissolution was evaluated through a field experiment. In all cores the recovered remains were dominated by fragments. As maximum, seven species were found: Biomphalaria peregrina (d’Orbigny, 1835), Drepanotrema kermatoides (d’Orbigny, 1835), Heleobia australis (d’Orbigny, 1835), H. parchappii (d’Orbigny, 1835), Pomacea canaliculata (Lamarck, 1801), Uncancylus concentricus (d’Orbigny, 1835) Musculium argentinum (d’Orbigny, 1835). We concluded that the TAZ extend from the surface to 25 cm approximately. The highest destruction takes place in the first 10 cm and decreases gradually in depth. In a similar way the specific richness and abundance of remains decrease downward through the TAZ, finding only H. parchappii and unidentified fragments towards the bottom. Dissolution was higher in shells without periostracum. No differences in dissolution were observed in depth.