INVESTIGADORES
HASSAN Gabriela Susana
congresos y reuniones científicas
Título:
Actualistic Taphonomy as a key for understanding the Holocene diatom record of the Argentine pampas
Autor/es:
HASSAN, GABRIELA S.; DE FRANCESCO, CLAUDIO G.; DIAZ, MARISEL
Lugar:
Montevideo
Reunión:
Workshop; First Workshop Actualistic Taphonomy in South America; 2017
Institución organizadora:
Universidad de la República, Facultad de Ciencias
Resumen:
Recent findings of noticeable changes in diatom preservation in the Holocene recordof Pampean shallow lakes evidenced the need of carrying out actualistic studies todecipher the environmental significance of taphonomic signatures. A series of fieldand experimental studies were conducted, focusing on the effect of contemporaryenvironmental gradients on the dissolution and fragmentation of diatom valves. Fieldstudies signaled salinity, carbonates and bicarbonates as the main drivers ofdissolution of the target taxa Cyclotella meneghiniana in shallow lakes covering wideenvironmental gradients. Laboratory controlled experiments demonstrated a negativeeffect of NaCl and HCO3Na on valve preservation, evidenced by an increase indissolved silica and by the occurrence of valves showing advanced stages ofdissolution. Although fragmentation was high in many lakes, the environmentalcauses of valve breakage could not be identified in the dataset. Detailed analysis oftaphonomic attributes and their relationship with live/dead agreement wereexamined in three lakes representing the lower salinity portion of the gradient.Results showed that low compositional fidelity was caused by differentialfragmentation of the most delicate taxa, rather than by dissolution biases. Theseresults indicated a strong link between compositional and taphonomic patterns atdifferent working scales, which was also evident in the sedimentary record of theselakes, as Holocene changes in diatom assemblage composition were highly correlatedwith taphonomic profiles. This correlation can be a consequence of the sameenvironmental characteristics influencing both preservation and composition, butalso taphonomy could be biasing assemblage composition by differentially destroyingdelicate taxa. This strong interdependence highlights the need of incorporatingtaphonomic studies in routine paleoenvironmental research. By doing so, diatompaleoecology would become benefited not only by incorporating clues on the qualityof compositional information but also by integrating taphofacies as a potential sourceof environmental information.