Paleoecología de niveles pelíticos de la sección superior de la Formación Hoyada Verde, Carbonífero superior, Precordillera de San Juan, Argentina

CISTERNA, G.A.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 1999 vol. 36 p. 259 - 267

0002-7014

ABSTRACT: PALEOECOLOGY OF THE UPPER SHALE LEVELS OF THE HOYADA VERDE FORMATION, UPPER CARBONIFEROUS, SAN JUAN PRECORDILLERA, ARGENTINA. Fifteen palaecommunities are recognized in a 26 m thick interval (Levipustula fauna) from the upper section of the Hoyada Verde Formation at its type locality. The palaeoecological analysis was based on Ausich´s component concept, which allows to enhance the importance of certain groups of the macrofauna and to infer which factors limited their distribution. Taking into account that biomass is a more adequate parameter than the numerical abundance for palaeoecological reconstructions, relative abundance was expressed as a percentage of the total biovolume. Diversity values were calculated using Shannon-Weaver´s index from biovolume data. These are reliable to estimate the physiological stress conditions in the studied assemblages. The palaecommunities are grouped in three sets, each one characterized its main component: brachiopod, bivalve and bryozoan communities. As a whole, the palaeoecological characteristics studied in each communities indicate a stable marine environment, such as an open platform with moderate bottom currents. However, the brachiopod communities show the highest diversity values and the bryozoan communities the lowest, suggesting small changes in the physiological stress conditions associated with the bottom currents in an environment not exposed to drastic changes. In general, this interpretation is consistent with postglacial transgression models which are have been proposed for the Late Paleozoic western Argentinian basins.