Actualistic taphonomy of freshwater diatoms: implications for the interpretation of the Holocene record in Pampean shallow lakes

HASSAN, GABRIELA S.; DE FRANCESCO, CLAUDIO G.; DIAZ, MARISEL

Actualistic Taphonomy in South America

Springer Nature Switzwerland

Lugar: Basilea; Año: 2020; p. 1 - 31

Recent findings of noticeable changes in diatompreservation in the Holocene record of Pampean shallow lakes evidenced the needof carrying out actualistic studies to decipher the environmental significanceof taphonomic signatures. In this chapter, we review a series of field andexperimental studies recently conducted, focusing on the effect of contemporaryenvironmental gradients on the dissolution and fragmentation of diatom valves.Field studies signaled salinity, carbonates and bicarbonates as the maindrivers of dissolution of the target taxa Cyclotellameneghiniana in shallow lakes covering wide environmental gradients.Laboratory controlled experiments demonstrated a negative effect of NaCl andHCO3Na on valve preservation, evidenced by an increase in dissolvedsilica and by the occurrence of valves showing advanced stages of dissolution.Detailed analysis of taphonomic attributes and their relationship withlive/dead agreement at a freshwater lake showed that within-lake taphofaciesare useful to discriminate between diatom sub-environments. The joint analysisof compositional and taphonomic variations in the recent sedimentary record of thelake demonstrated the usefulness of taphonomic analyses to uncover subtlepaleoenvironmental variations, which could be overlooked if only traditionalcompositional analyses were performed. The strong link between compositionaland taphonomic patterns at different working scales highlighted the usefulnessof including taphonomic analyses when conducting diatom-basedpaleoenvironmental studies in environmentally heterogeneous shallow lakes.