Comunidades bentónicas en facies carbonáticas del Ordovícico (inferior-medio) de la Precordillera Argentina

Abstract

F-rom a biov.)iumetí-ic study and ínultivaríat.c analysís of cight oncroflaunal asscmblages th rough the San Juan Format o o (Larí y Orolovician) in Quebrada Ancha (Sierra cíe Talacasto) two major comiuunitv groups are clisuinguished: sponge--dominatecl anol brachiopad--otonunateol communitics. Ibree allogcnic- limiting factors ~illecteol prima- the Consejo Nacional dc Investigaciones Científicas y Técnicas ((ONI(TF13. ¡ (:3íed,< cíe Esiíxiíigraiía x Geología 1 lisiórica, Faculiad cíe (Tiencias Exactas. Físicas x Na-turalcs. tjniversiolaol Nacional ole (Tóroloha. Av. Veles Sarsficlol 299: (5001)) CTóreiob:i. Arce orino. 140 T. M. Sánchez, B. G. Waisfeld, M. Carrera, 5. Toifolo rily distribution of thcse eommunities. The turbidity effect is a first order factor that Icad to the differentiation of the two major groups (sponge-dominated aud brachiopoddominated); the substrate and prevalent encrgy conditions are second order factors that controlled biovolumetrie abundance within each group. These changes in communities structure through the vertical stratigraphic profile suggest a posible sea level falí during the Late Arenigian at the lower part of the section, followed by a sea level rise, well documented at the top the sequence (Llanvirn).