Miocene free-living bryozoans from Patagonia

HÅKANSSON, E.; CASADÍO, S.; PARRAS, A.

Conferencia; International Bryozoology Association - 13th Conference, Concepción, 2004; 2004

Cupuladriids are reported for the first time from Patagonia, southernmost South America, where at least two species ? Cupuladria sp. and Discoporella sp. ? have been collected from upper Miocene strata. Miocene deposits in Patagonia, southern Argentina, constitute a comparatively thin sedimentary wedge deposited in an epicratonic basin related to the passive continental margin bordering the Atlantic Ocean. These deposits include a series of spectacular mollusk-bryozoan-dominated shell concentrations comprising the Puerto Madryn Formation. Well-developed exposures of this unit are located around Puerto Pirámides, Penísula de Valdés. Here the preserved section shows a vertical succession of facies passing from open mid-shelf to more shallow, shoreface to foreshore environments characterized by upward-coarsening cycles capped by condensed shell-beds. Whereas bryozoans in general are plentiful throughout the entire section, the free-living bryozoans appear to be restricted to a number of distinct horizons through the middle part of the formation, where they occur in fair amounts in fine sands with minor mud content. The biogeographic and phylogenetic implications of the new find will be discussed.