Paleoecological and paleobiogeographic considerations of Ordovician graptolites from the

VENTO, BARBARA; TORO, BLANCA; MALETZ, JÖRG

HISTORICAL BIOLOGY

Taylor & Francis

Lugar: Londres; Año: 2013 p. 37 - 41

0891-2963

ABSTRACT: We analyze new paleoecological data from South American graptolite records to understand the patterns that influence the space-tempo distribution of the group. In addition, a cluster analysis including taxa from the Baltograptus cf. B. deflexus and Didymograptellus bifidus Zones is carried out to evaluate the paleogeographic relationships between Northwestern Argentina and the others regions in the world. Three different biofacies was recognized in the Acoite Formation. The first biofacies takes place in the lower part of the unit, corresponding to pelitic levels (T. phyllograptoides and T. akzaharensis Zones). The other two biofacies belong to the endemic or neritic shallow water environments, and develop in deposits corresponding to the middle part of the Acoite Formation (bottom of the Baltograptus cf. B. deflexus Zone) in the Sierra de Aguilar, and in the upper half of the unit exposed at Los Colorados area (Didymograptellus bifidus Zone), respectively. The statistical analysis highlight the paleobiogeographic relationship between Northwestern Argentina and southwestern China during the middle and upper Floian (Baltograptus cf. B. deflexus and Didymograptellus bifidus zones), and it supports the hypothesis that during Early Ordovician north-western Argentina was located in the middle to high latitudes, included in the cold water faunas realm.