Silurian-Devonian coral associations across a sequence stratigraphic boundary in the Argentine Precordillera.

CARRERA MARCELO G.; MONTOYA, E.; RUSTAN, J; HALPERN, K

GEOLOGICAL JOURNAL (CHICHESTER)

JOHN WILEY & SONS LTD

Año: 2013 vol. 48 p. 256 - 269

0072-1050

Abstract. Silurian and Devonian corals abundantly occur in siliciclastic rocks of the Argentine Precordillera. Three main coral associations are recognized and described. They are distributed along a Silurian storm-dominated shallow platform, a transitional restricted nearshore environment and a Devonian muddy platform setting. Four main associations of rugose and tabulate corals have been recorded: The Silurian association, a transitional coral fauna and two coral associations in the Devonian rocks. The Silurian shallow platform coral association shows abundant colonies of a tabulate pleurodictyform coral. The type and the domical form of corals indicate high energy environments. The transitional reddish mudstone coral association shows the abundance of the tabulate coral Argentinella argentina which could have formed patches in protected low energy environments. There are two different corals associations in the Devonian muddy platform: The first one includes rugose and hemispherical tabulate corals. The second group corresponds to tabulate corals assigned to Parastriatopora sanjuanina, and Parastriatopora sp. They are long stick-like, fasciculate forms, grouped in apparently life position. Rugose and tabulate corals in the Upper Silurian and Lower Devonian of Argentina constitute low diversity associations of western Gondwana, developed in mid to high latitudes. An important faunal turnover was detected across the studied interval. The domical Pleurodictyform and some associated fauna disappeared.  The Family Parastriatoporidae first occurs in the reddish mudstone association (Argentinella) for later diversified in two different morphotypes. The pattern observed in the Argentine Precordillera indicates that during the regressive stages biofacies migrate offshore, to peripheral platform areas. The selective pressure produce high levels of extinction and in a few cases the development of autochthonous species and subsequent diversification. DOI: 10.1002/gj.1332 DOI: 10.1002/gj.1332 DOI: 10.1002/gj.1332 DOI: 10.1002/gj.1332