IIMYC   23581
INSTITUTO DE INVESTIGACIONES MARINAS Y COSTERAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Differential preservation of the snail Heleobia parchappii (d?Orbigny) in freshwater and saline shallow lakes of the Argentine pampas
Autor/es:
DE FRANCESCO, CLAUDIO GERMÁN; HASSAN, G.S.
Lugar:
Montevideo
Reunión:
Workshop; Workshop Actualistic Taphonomy in South America (TAAS 2017); 2017
Resumen:
It has beenobserved that in Holocene lacustrine successions of the Pampa Plain (Argentina),mollusk assemblages deposited under inferred brackish-saline lake conditionsexhibit higher abundance and better preservation than those deposited infreshwater, suggesting that preservation may be strongly related to salinity inthese environments. To explore this hypothesis, we conducted an actualistic field-basedstudy of live/dead fidelity and preservation of the euryhaline mud snail Heleobia parchappii (target species) insix shallow lakes representing a gradient of salinity (between 0.5 and 42 ppt).Live/dead fidelity included the comparison of the abundance and size of shellsoccurring alive (LA) with those occurring dead (DA). Preservation was evaluatedthrough the analysis of shell fragmentation and surface alteration in DAs. Live/deadfidelity in abundance was poor. Dead shells were more abundant in higher salinelakes whereas live snails showed their lowest abundance here. This pattern wasmore evident in DAs deposited over the littoral shore of lakes (olderassemblages) suggesting a taphonomic origin for such concentrations. Shell sizewas similar between LAs and DAs, suggesting a good live/dead fidelity. Fragmentation was lower in the most saline lakes, suggestingless destructive conditions for postmortem preservation. Shell surfacealteration did not show significant differences among lakes. These preliminaryresults highlight the importance of lake salinity as a possible taphonomicagent that promote mollusk preservation. It is possible that the highertaphonomic alteration of shells in freshwater may be related to changesproduced by microbial maceration of organic matrix, as these lakes are far moreproductive than saline ones. While experimental studies addressing the causesof shell alteration in freshwater lakes are needed, the present findingsprovide evidence in that direction, with implications forexplaining the high concentration of well-preserved shells usually found inHolocene sedimentary successions.