CASADIO Silvio Alberto
Encrusting and boring barnacles through the Cretaceous/Paleogene boundary in northern Patagonia (Argentina)
BREZINA, S.; ROMERO, M. V.; CASADÍO, S.
ASOCIACION PALEONTOLOGICA ARGENTINA
Lugar: Buenos Aires; Año: 2017 vol. 54 p. 107 - 123
Abstract. Information about barnacles as fossil components of hard substrate communities from middle latitudes in the Southern Hemisphereis scarce. Changes in these barnacle communities during episodes of extinction, such as that which occurred during the Cretaceous/Paleogene(K?Pg) boundary, are almost unknown. We describe encrusting and boring barnacles associated with Maastrichtian and Danian oysters,evaluate the involved taphonomic processes and report changes in their frequencies over time. A total of 1,174 valves belonging to nineoyster species, collected from the Jagüel and Roca formations of the Neuquén Basin, were analyzed. Presence/absence of barnacles or theirbioerosional traces were recorded, frequencies of host incrustation and bioerosion were calculated and taphonomic and statistical analyseswere performed. The encrusting barnacles identified on the oyster shells were assigned to Verruca rocana and, their traces, to the ichnospeciesCentrichnus concentricus Bromley and Martinell. The boring barnacles are represented by traces assigned to the ichnogenus Rogerella. A preliminarytaphonomic analysis indicated that late Maastrichtian and early Danian shells presented a fair-poor condition given by abrasion and fragmentationas taphonomic attributes while late Danian shells exhibited mostly good-fair or mixed condition for both attributes. Verruca rocanawas not recorded during the late Maastrichtian but high frequencies of encrusted valves did become apparent after the K?Pg boundary. Boringbarnacles represented by the trace Rogerella exhibited a decline in abundance during the early Danian but an increase during the late Danian. Boththe encrusting and the boring barnacles associated with oysters presented an increase in their frequencies during the late Danian.