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

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.