CICYTTP   12500
CENTRO DE INVESTIGACION CIENTIFICA Y DE TRANSFERENCIA TECNOLOGICA A LA PRODUCCION
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Early appearance of Lueckisporites virkkiae in South America and global Lower Permian biostratigraphic and paleobiogeographic significance
Autor/es:
DI PASQUO, M.M.; GRADER, GEORGE; ISAACSON, P.; IANNUZZI, R.; SOUZA, PAULO ALVES; DIAZ-MARTINEZ, E.
Lugar:
Rio de Janeiro
Reunión:
Simposio; XIV Simpósio Brasileiro de Paleobotânica e Palinologia; 2013
Institución organizadora:
Museu Nacional/Universidade Federal do Rio de Janeiro
Resumen:
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.