EOPALEOZOIC PATAGONIA–EAST ANTARCTICA CONNECTION: FOSSIL AND U-Pb EVIDENCE FROM EL JAGÜELITO FORMATION

NAIPAUER MAXIMILIANO; SATO, A.M.; GONZALEZ, PABLO; CHEMALE JR. FARID; VARELA RICARDO; LLAMBÍAS, E.J.; GRECCO, GERSON; DANTAS, ELTON

Brasilia, Brasil

Simposio; VII South American Symposium on Isotope Geology; 2010

Universidad de Brasilia

The analysed samples suggest for the El Jagüelito Formation a main population (>50%) peaked at 523 Ma (Early Cambrian) and 580 Ma (Late Neoproterozoic), and a secondary one (<30%) with ages in the surroundings of 1000 Ma (Late Mesoproterozoic). This pattern may reflect a typical Gondwanan provenance. The Early Cambrian peak may be correlated with the Pampean orogen of Argentina and Ross-Delameryan orogen of the Antarctica-Australia (cf. Terra Australis orogen, Cawood 2005). It constrains the maximum depositional age of El Jagüelito Formation, which is slightly younger than that of Pankhurst et al. (2006, c. 535 Ma, see Fig. 1). The Late Neoproterozoic peak may be associated with zircons derived from rocks formed during the Brasiliano and Pan-African orogenies, while the Late Mesoproterozoic peak may be correlated with a provenance from rocks related to the Grenville and Natal-Namaqua orogens in different paleogeographic sources during the Gondwana assembly. Despite the above mentioned variable provenance possibilities, the Antarctic connection of the Archeocyath fossils strongly support the idea that the East Antarctic region was the sedimentary source for the El Jagüelito Formation. In addition to that, the Early Cambrian to Early Ordovician Douglas Conglomerate (Byrd Group, Transantarctic Mountains) contains archeocyathan limestone blocks from Shackleton Limestone (Atdabanian-Botomian) and exhibits a detrital zircon pattern with a main peak at 520 Ma and a secondary one at 1050Ma (Goodge et al., 2004), which is very similar to the meta-conglomerate sample AB-282. This comparison argues for a correlation between Douglas Conglomerate and our meta-conglomerate AB-282. These results open the possibility that part of the Northern Patagonia has a para-autochthonous origin and East Antarctic affinity.