MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
artículos
Título:
Palynological record of the Paleogene Río Leona Formation (southernmost South America): stratigraphical and paleoenvironmental implications
Autor/es:
BARREDA, V.; PALAZZESI, L.; MARENSSI, S.
Revista:
REVIEW OF PALAEOBOTANY AND PALYNOLOGY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2009 vol. 154 p. 22 - 33
ISSN:
0034-6667
Resumen:
Terrestrial palynomorph assemblages have been
recovered from the Río Leona Formation, southwestern Santa Cruz Province,
southern South America. Organic debris (spores, pollen grains, fresh water
algae, plant tissues and fungi) are preserved in shales associated with other
plant fossil remains (leaves and wood). The Río Leona Formation is here assigned
to the early Late Oligocene based on the presence of key species of the M-M
palynological zone (Margocolporites tenuireticulatus Barreda, Diporites aspis
Pocknall and Mildenhall, Granodiporites nebulosus Partridge, Mutisiapollis spp.)
and the virtual absence of warmth-adapted taxa (abundant from the latest Late
Oligocene to Middle Miocene in Patagonia). A temporal gap between the Río Leona
Formation and the overlying Centinela Formation (Early Miocene) -exposed in the
studied region- is suggested
here
based on the differences observed in their palynological
assemblages. The Río
Leona Formation was deposited in a continental environment, with local peat swamps
and coastal plain environments. The presence of Antarctic palynomorphs in the
lower and middle sections of the Río Leona Formation is consistent with the
cooling trend globally recognized during the Late Eocene and Early Oligocene
times. The appearance of some Neotropical families in the upper section might
indicate the beginning of the globally recognized Late Oligocene warming event.
Records of Asteraceae (Mutisiapollis telleriae Barreda and Palazzesi sp. nov.),
Menyanthaceae (Striasyncolpites laxus Mildenhall and Pocknall), and Rosaceae (Psilatricolporites
quenua Barreda and
Palazzesi sp.nov., Psilatricolporites sp.) are the oldest reports in Patagonia to date,
and provide significant information on the early divergence and radiation times
of these major angiosperm families.