Early appearance of Lueckisporites virkkiae in South America and global Lower Permian biostratigraphic and paleobiogeographic significance

DI PASQUO, M.M.; GRADER, GEORGE; ISAACSON, P.; IANNUZZI, R.; SOUZA, PAULO ALVES; DIAZ-MARTINEZ, E.

Rio de Janeiro

Simposio; XIV Simpósio Brasileiro de Paleobotânica e Palinologia; 2013

Museu Nacional/Universidade Federal do Rio de Janeiro

Lueckisporites virkkiae Potonié and Klaus originates during the Artinskian and is a key palynomorph species applied in biostratigraphic schemes in South America and elsewhere. In central Bolivia at Apillapampa, L. virkkiae was recently recovered in the 350m thick Copacabana Formation. Older studies here attributed this unit to the Asselian through Artinskian based on conodonts, foraminifera, fusulinaceans, and palynomorphs. New microfossil and ID-TMS U-Pb radiometric zircon data confirm that most of the marine, lower part of the Copacabana Formation at Apillpampa is Asselian to early Sakmarian, yet L. virkkiae occurs at 69m between two Asselian ashes at 40m and 120m dated as 298 and 295.2 Ma. The overlying transitional Coal Member occurs above a sequence boundary zone and is Artinskian based on palynomorphs and plants. The Coal Member could be older based on an early Sakmarian ash date (291.6 Ma) occurring near its base at 242m. Assuming the absolute ages are correct, the appearance of L. virkkiae does not match its previous oldest known record (281.4 + 3.4 Ma, middle Artinskian), radiometric dates obtained from the upper portion of the Rio Bonito Formation in Brazil. This disagreement between palynozone ages containing L. virkkiae in South America is addressed herein. Moreover, other absolute ages from the sections where this taxon occurs in Argentina and Uruguay are younger: a mid-Artinskian age is given for their bases even if they do not come exactly from the base of their corresponding zones Lueckisporites-Weylandites and Striatoabieites anaverrucosus-Staurosaccites cordubensis. Other Artinskian appearances of L. virkkiae are also known from outside South America, but very few are constrained with radiometric data. Most of the FODs of this taxon from outside South America are Kungurian to Wordian, its LOD in SAM is regarded as Wordian/Capitanian. Furthermore, outside this region L. virkkiae ranges to the end of the Permian. Triassic records are generally interpreted as reworked. This work suggests that L. virkkiaeis important as a biostratigraphic marker of mostly local significance. From its geographic distribution throughout the Permian, one possible interpretation could be that its inception was progressively younger stemming from central Bolivia during the mid-Asselian and radiating to Argentina, Brazil and Uruguay and places in Africa during the Artinskian, finally reaching more distal parts of Gondwana and elsewhere during the late Cisuralian, Guadalupian and Lopingian. Finally, plant remains recovered from the Coal Member of the Copacabana Formation at Apillpampa were attributed to the somewhat younger Glossopteris Flora. This palynological information extends the record of several groups of plants characteristic of this floral realm to the mid-Asselian.