The presence of Cimmeriella Archbold & Hogeboom and Jakutoproductus Kaschirtzev in Patagonia

TABOADA, ARTURO CÉSAR; PAGANI MARÍA A

Trelew, Argentina

Workshop; the Carboniferous-Early Permian Stratigraphy, Paleontology, Paleogeography and Paleoclimatology of; 2009

MEF-LIEB, FCN-UNPSJB

Late Paleozoic marine beds from Patagonia have yielded an abundant and diverse fauna including brachiopods, bivalves, gastropods, cephalopods, hyolithids, echinoderms, cnidarians, ostracods and scarce trilobites. However, microfossils remains (foraminifers and conodonts) have not been recorded so far. The faunal succession at the Tepuel-Genoa Basin is relatively well known, although not entirely described, particularly from southernmost localities that show a predominance continental facies (Río Genoa Formation), where a more intensive sampling is needed in order to have a complete biostratigraphical scheme of the whole basin. In this contribution we described two new brachiopod species belonging to the genera Cimmeriella and Jakutoproductus recovered from the Cisuralian deposits of the Tepuel-Genoa basin. Cimmeriella sp. occurs in upper levels of the Mojón de Hierro Formation, whilst records of Jakutoproductus sp. come from the Río Genoa Formation. These new findings have transcendent paleobiogeographical significance and allow identifying conspicuous early Permian biotic events in Patagonia, which are valuable for regional and intercontinental correlations, in special with mid-high latitude faunas from both hemispheres. The upper Mojón de Hierro Formation faunal assemblage includes Cimmeriella sp. nov., the brachiopods Costatumulussp., Spirelytha sp., Quinquenella sp., Brachythyrinella sp., Arctitetra sp., and Neochonetes sp., and is tentatively assigned to the late Sakmarian (Sterlitamakian). With the exception of Costatumulus and Neochonetes (with different species), neither of the mentioned genera is at the moment recorded in the localities in the Rio Genoa Formation. The Jakutoproductus assemblage from Rio genoa Formation is basically characterized by two species of this genus and can be regarded as slightly younger than the previous Cimmeriella assemblage based on the Permian evolutive tendencies known for the Jakutoproductus and its distribution of the Russian species of Jakutoproductus. As a result, the present correlation levels between the Mojon de Hierro and Rio Genoa formations based on the faunal content should be partially reconsidered in light of these new findings. The Cimmeriella assemblages occurred in early Permian beds from Western Australia (Callytharra Formation and Wooramel Group of the Carnavon basin). The common occurrences of the widespread key genus Cimmeriella also in Patagonia, allows to refine a proposal of intercontinental correlation between both last regions, which probably would also had been under similar paleolatituds and paleoclimatic conditions. In this way the Cimmeriella fauna in Patagonia could be likely correlate with the Strophalosia irwinensis Zone. On the other hand, Patagonia assemblages could be somehow compared with assemblages from the Boreal Realm that share the bipolar genera Verchojania, Jakutoproductus and Cimmeriella. Besides Patagonia, the only another region where Cimmeriella and Jakutoproductus occurs in a stratigraphic succession, is the Yukon Territory, Arctic Canada, where they were recorded in the upper member of the Jungle Creek Formation. Jakutoproductus species are also known from Northeastern Asia where they  characterize marine assemblages that lived in the surrounding Angaraland marginal seas. In this regard, the Munugudzhakian Superhorizon of the Kolyma-Omolon regions and its partially correlative regional sections as well as the Upper Kygyltassian and Khorokytian Horizons of Verchojan area, could be broadly correlated with the Mojon de Hierro and Río Genoa formations of Patagonia based on the co-occurrence of the couple Verchojania and Jakutoproductus.