Early Cambrian archaeocyathan limestone blocks in low-grade meta-conglomerate from El Jagüelito Formation (Sierra Grande, Río Negro, Argentina)

Authors

  • P.D. GONZÁLEZ Centro de Investigaciones Geológicas, (UNLP - CONICET) 1 Nº 644, B1900TAC, La Plata (Buenos Aires), Argentina. Fax: +54-221-4827560
  • M.F. TORTELLO CONICET – División Paleozoología Invertebrados, Museo de Ciencias Naturales. Paseo del Bosque s/n, 1900 La Plata (Buenos Aires), Argentina.
  • S.E. DAMBORENEA CONICET – División Paleozoología Invertebrados, Museo de Ciencias Naturales. Paseo del Bosque s/n, 1900 La Plata (Buenos Aires), Argentina.

Keywords:

Archaeocyatha, Early Cambrian, El Jagüelito Formation, Low-grade metamorphism, North Patagonian Massif, Argentina

Abstract

Massive grey limestone blocks containing a fairly diverse but poorly preserved archaeocyath fauna were recovered from a meta-conglomerate bed in the El Jagüelito Formation (Sierra Grande area, Eastern North Patagonian Massif, Río Negro, Argentina). This is the first documented reference of the presence of archaeocyaths in continental Argentina. Seven different taxa were identified, preliminary described and figured. Recrystallization of the skeletons due to regional low-grade metamorphism and deformation of the unit does not allow observation of key detailed features and prevents identification to genera and species. Nevertheless, the specimens studied show general affinities with archaeocyathan assemblages from the Australia-Antarctica palaeobiogeographic province and indicate a middle Early Cambrian (Atdabanian-Botomian) maximum age for the deposition of the El Jagüelito Formation protoliths. The similarities between the North Patagonian Early Paleozoic El Jagüelito Formation and those rocks from Antarctica suggest a geologic and biologic common history of these regions on the same southwest margin of Gondwana during that time.

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Published

2011-07-14

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Section

Articles