An Early Givetian land plant and palynoassemblage and its biostratigraphical significance.

MATSUMURA, W.; IANNUZZI, R.; DI PASQUO, M.M.; BOSETTI, E.

FLOrianopolis

Simposio; IX Simpósio Sul-Brasileiro de Geologia- II Workshop de Recursos Minerais da Região Sul; 2015

ufrgs

Several Middle Devonian (Eifelian-Givetian) deposits bearing early land plants in South America have been described in Argentina, Bolivia, Brazil, Colombia, Falkland Islands and Venezuela. In general, these sections are palynologically productives in most of those countries except for Venezuela and Colombia, probably because they are still not well explored. Nevertheless, it is not frequent to have palynology from the same plant level due to a sandier composition rather than a more shaley-silty nature. Furthermore, an intense oxidation (weathering) of Middle Devonian rocks prevents a reliable stratigraphic position and correlation of such levels. Here we present the first Early Givetian section in Paraná Basin based on co-occurrence of land plants, palynomorphs and marine invertebrates. The Vila Ricci outcrop is located in Ponta Grossa Municipality, state of Paraná, southern Brazil, and composed of dark to light gray shales with parallel lamination, siltstones and fine to medium-grained sandstones. This section was preliminarily studied in 1970s and no longer visited due to activities of Industrial Company Cerâmica Sul-Brasil. Recently, the locality was exposed for the earthworks activities allowing sampling for palynology before the weathering acts over it. Land plants (Spongiophyton sp., Palaeostigma sp. and Haplostigma sp.), trilobites calmoniids and crinoids (Ctenocrinus sp.) were recognized only at the base, from where three palynological samples were collected. Several ichnofossil types and plant debris occurs in the whole outcrop. Plant remains can be assigned to Plant fragment and Plant debris Taphofacies. The three palynoassemblages obtained yielded well preserved and diverse miospores (e.g. Acinosporites eumammillatus, Dibolisporites farraginis, Geminospora lemurata, Grandispora pseudoreticulata, Leiotriletes balapucensis), acritarchs/prasinophytes (e.g. Arkonites bilixus, Evittia sommeri, Hemiruptia legaultii, Pterospermella pernambucensis, Unellium piriforme) and chitinozoans (Ramochitina ramosi). An Early Givetian age is supported based on co-occurrence of diagnostic species G. lemurata and R. ramosi, and correlated to the G. lemurata-C. ligurata Zone Melo and Loboziak. This age is given for the new plant assemblage associated. Similar land plant and palynoassemblages were also recognized in the Angosto del Pescado in northern Argentina, and Balapuca, Yesera and Mataral areas in Bolivia. Keywords: Paleobotany, Palynology, Middle Devonian, Paraná Basin. [CNPq 141979/2011-9; PQ 309211/2013-1; PQ 311483/2014-3]