INVESTIGADORES
GARCIA Victoria Josefina
congresos y reuniones científicas
Título:
ORIGIN AND EVOLUTION OF THE EARLY LAND PLANTS IN ARGENTINA AND SOUTH AMERICA THROUGH THE PALYNOLOGICAL RECORD
Autor/es:
CLAUDIA VIVIANA RUBINSTEIN; VICTORIA JOSEFINA GARCÍA; PHILIPPE STEEMANS
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress. The history of life: A view from the Southern Hemisphere; 2014
Institución organizadora:
CONICET
Resumen:
The worldwide first evidence of land plants comes from
the Central Andean Basin (CAB) in northwestern Argentina, where a diverse
cryptospore assemblage composed of five genera pushes backward the beginning of
the colonization of continents until c. 471-473 Ma. This finding in
Dapingian (early Middle Ordovician) rocks of the CAB confirms the first
appearance of land plants in the Gondwana palaeocontinent. Upwards, in the same
locality, low-diverse and commonly not well-preserved cryptospores were found
in Darriwilian and Hirnantian rocks. The non-continued cryptospore record could
be related to the Ordovician foreland basin and particularly to the marine
marginal deposits with frequent sea level changes. However, in the Precordillera
Basin, scarce and low-diversified cryptospores, mainly represented by naked
tetrads, have been found in the Sandbian and Katian. It should be noted that
these deposits correspond to a tectonically complex palaeoenvironment, related
to the accretion of the Precordillera terrane to the western Gondwana margin
during the Middle-Late Ordovician. The CAB latest Ordovician deposits, related
to the Hirnantian glaciation, yielded one of the most abundant and diversified
Ordovician cryptospore assemblages worldwide. To date, palynological data from
other Ordovician basins of South America are sparse, and there are no records
of land-derived palynomorphs outside Argentina. The oldest record of trilete
spores in South America comes from the Hirnatian glacial deposits of the CAB
and is represented by the Ambitisporites avitus- dilutus Morphon.
Surprisingly, no trilete spores were found in the Lower Silurian (Llandovery)
of Argentina, neither in the CAB nor in the Precordillera. Meanwhile, the Ambitisporites
avitus- dilutus Morphon first appears in Paraguay, in the late Aeronian of
the Parana Basin and the Archaezonotriletes chulus- nanus Morphon in
Brazil, in the Telychian of the Parnaiba Basin. In the Wenlock of the
Precordillera some taxa such as Archaezonotriletes chulus- nanus
Morphon, Retusotriletes sp. and Emphanisporites sp. have been
recognized while there are not other records of land-derived palynomorphs from
the Wenlock of South America. The Late Silurian was a period when the richness
and diversity of trilete spore assemblages significantly increased,
particularly in the Argentinian Precordillera and the Brazilian Amazon Basin.
Among the South American trilete spores, taxa considered as biostratigraphic
markers for the Late Silurian- Early Devonian, allow correlation with biozones
established for Euramerica, Gondwana and Peri-Gondwanan terranes. Similarities
between terrestrial palynomorphs from South America and those from other
palaeocontinents and palaeolatitudes, suggest a cosmopolitan distribution for some
species of the Late Silurian flora.