Archaeocyaths from South America: review and a new record

Abstract

In South America, autochthonous archaeocyathan faunas preserved in Early Cambrian limestones have not been found yet. Nevertheless, a few well‐documented occurrences of these fossils in clasts contained in coarse‐grained rocks of a wide age range have been discovered in recent years. Erratic limestone blocks from the Late Carboniferous–Early Permian Fitzroy Tillite Formation in the Falkland/Malvinas Islands yielded three archaeocyath taxa. Also, seven taxa were reported from archaeocyathan limestone clasts in a metaconglomerate of the Cambro‐Ordovician El Jagüelito Formation in northern Patagonia. In addition, a new record from the Late Carboniferous–Early Permian Sauce Grande Formation diamictites in Sierras Australes, Buenos Aires Province, Argentina, is presented herein. Preservation of this scarce new material is poor, but at least three different taxa can be distinguished. The most likely source of all archaeocyathan limestone clasts found in southern South America is the Shackleton Limestone from the Transantarctic Mountains in East Antarctica. The new record from the Sauce Grande Formation and the inferred clast provenance reinforce the correlation between this unit, the Dwyka Tillite (South Africa) and the Fitzroy Tillite Formation (Falklands/Malvinas), suggesting a very wide distribution of these Antarctic occurrences during the Late Carboniferous–Early Permian Gondwana glaciation (Episode III). Thus, even though being allochthonous, archaeocyaths are emerging as a new key biological feature for Gondwana palaeogeographic reconstructions. Copyright © 2012 John Wiley & Sons, Ltd.

Patagonia: where does it come from?

“…This metaconglomerate contains clasts of the underlying limestones and is petrographically quite similar to the El Jagüelito Formation metaconglomerate (González et al, 2011a). It is evident that the Transantarctic Mountains limestones were the source of limestone blocks and erratics for a very long time, as has been proposed for the fossiliferous Permo-Carboniferous tillites from Antarctica (Debrenne and Kruse, 1986), South Africa (Debrenne, 1975), the Malvinas Islands (Keidel, 1916;Stone and Thomson, 2005), the Sierra de la Ventana tillites (González et al, 2013), as well as for recent moraines (Hill, 1965).…”

“…The Nimrod Group is exposed only in the Miller Range (Fig. 3) where it yields ages ranging from Archean to Paleoproterozoic (Goodge et al, 1993a). Rocks as old as the Nimrod Group are not known in Patagonia, although some zircon cores from orthogneisses with inherited Archean ages have been reported (Rolando et al, 2002;Chernicoff et al, 2013).…”

The Late Paleozoic Tectonometamorphic Evolution of Patagonia Revisited: Insights From the Pressure‐Temperature‐Deformation‐Time (P‐T‐D‐t) Path of the Gondwanide Basement of the North Patagonian Cordillera (Argentina)

“…However, the tectonic significance of this key orogenic event is still under debate and has been alternatively attributed to collisional or accretional tectonics (e.g., Gregori et al, 2008Gregori et al, , 2016Heredia et al, 2017Heredia et al, , 2018Hervé et al, 2016;Pankhurst et al, 2006;Prezzi et al, 2018;Ramos, 2008;Varela et al, 2015;Vizán et al, 2015Vizán et al, , 2017von Gosen, 2003). These proposals have in turn led to contrasting hypotheses about the origin of the North Patagonian massif, for which an allochthonous, autochthonous, or para-autochthonous origin has been inferred (Castillo et al, 2017;Dalla Salda et al, 1992;González et al, 2011González et al, , 2012González et al, , 2018Gregori et al, 2008;Heredia et al, 2018;Pankhurst et al, 2006Pankhurst et al, , 2014Ramos, 1984Ramos, , 2008Ramos & Naipauer, 2014;Rapalini et al, 2010Rapalini et al, , 2013.…”

Geology reviewed for the Falkland Islands and their offshore sedimentary basins, South Atlantic Ocean

“…All of the archaeocyathan limestone was thought to have originated in the Transantarctic Mountains, but recent discoveries in Argentina (González et al . 2013) have added a new dimension to the regional picture that is not yet fully appreciated.…”