COMPOSITION AND STRUCTURE ANALYSIS OF THE BENTHIC MARINE ASSOCIATIONS FROM THE LEVIPUSTULA LEVIS BIOZONE FROM CENTRAL WESTERN ARGENTINIAN BASINS

HALPERN, K.; CISTERNA, G.A.; BALSEIRO, D.; STERREN, A.F.

Evento virtual

Otro; 1er Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina; 2020

Asociación Paleontológica Argentina

Despite being coeval faunas from the Levipustula levis biozone from the Late Paleozoic western centralArgentinian basins, Levipustula and Aseptella-Tuberculatella/Rhipidomella-Micraphelia (AT/RM)associations show high compositional differences suggesting that their wide vs. restricted distributionis probably linked to a set of abiotic factors. We hypothesize that bathymetric preferences fromdominant genera could partly explain some of their paleoecological differences. We describe andcompare the faunas? structure at a regional scale using a proportional rank plot and estimated richnessby rarefaction based on a generic occurrence data set. We also use an index for each genus?environmental preferences according to their occupancy along the bathymetric gradient. TheLevipustula association is more diverse than AT/RM fauna. First, it is co-dominated by brachiopods(57%) and bivalves (43%), while the AT/RM fauna is brachiopod-dominated (>70%). Higher richness andevenness indicate that the Levipustula association would develop in more heterogeneousenvironments than the AT/RM association. Moreover, a higher dominance of brachiopods in the AT/RMassociation could be a paleoecological response to environments with low turbidity. So far, thebathymetric distribution assessment indicates that the AT/RM association exhibits preferences fordeep waters while taxa with broader bathymetric affinities characterize the Levipustula association.Hence, the less diverse AT/RM association bearing deep-water specialists could have developed undergreater glacial-influence in low turbiditic fjord-like environments, whereas the generalist Levipustulaassociation could have occurred in open marine settings.