INVESTIGADORES
GARCIA Victoria Josefina
congresos y reuniones científicas
Título:
THE EVOLUTION OF EARLY PALAEOZOIC MARINE PHYTOPLANKTON AT THE ACTIVE CONTINENTAL MARGIN OF WESTERN GONDWANA (ARGENTINA)
Autor/es:
CLAUDIA VIVIANA RUBINSTEIN; VICTORIA JOSEFINA GARCÍA
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress. The history of life: A view from the Southern Hemisphere; 2014
Institución organizadora:
CONICET
Resumen:
The southern South American margin of Western Gondwana
was active from the Neoproterozoic to the Mesozoic, until the break-up of the
palaeocontinent. In this context, during the early Palaeozoic, this margin was
strongly affected by successive episodes of subduction and accretion of
terranes. Consequently, the basins related to this margin had a complex
geodynamic history that should have influenced diversity trends of marine
organic-walled phytoplankton. The oldest marine phytoplankton assemblage, low
in abundance and diversity and poorly preserved, comes from the Late Cambrian
of the Cordillera Oriental, Central Andean Basin. The Early Ordovician displays
a gradual increase of diversity during the Tremadocian, with the remarkable
presence of the Gondwanan characteristic messaoudensis-trifidum
acritarch assemblage in the Late Tremadocian. The highest Ordovician diversity
corresponds to the Floian platform facies of the Central Andean Basin. The
Middle Ordovician shows a progressive decline of diversity. However, it must be
taken into account that the Dapingian and Darriwillian marine phytoplankton
comes mainly from estuarine-deltaic facies of the outermost part of the
proto-Andean foreland basin. The diversity dramatically diminishes during the
Sandbian and Katian in coincidence with thickening-coarsening facies related to
the progradation of a deltaic system. The Hirnantian glacial-related deposits
record a new peak in diversity throughout all the foreland basin systems of the
Central Andean Basin. The peri-Gondwana volcanic arc deposits of the Famatina System
yielded rich and diverse Lower to Middle Ordovician phytoplankton assemblages,
even if they show noteworthy differences with coeval assemblages of the Central
Andean Basin. The Ordovician of the Precordillera terrane, marked by its
accretion to the Gondwana margin, yielded sparse and poorly diversified Middle
to Late Ordovician phytoplankton assemblages. During the Silurian, the marine
phytoplankton flourishes with an increase of diversity starting from the
Llandovery in both the Precordillera and the Central Andean foreland basins. A
new biostratigraphic scheme recently proposed for the Silurian deposits of the
Precordillera allows the recognition of the Wenlock, highly questioned in this
basin. The diversity of the marine phytoplankton during the Wenlock remains
quite similar. The highest marine phytoplankton diversity of the whole Silurian
is documented in the Ludlow of the Precordillera, particularly in shaly-predominant
sediments that correspond to a low-energy open shelf environment. Towards the
top of the Silurian sequence, the transition to an inner shelf exposed to storm
activity and a shoreface, is accompanied by a decrease of the diversity in the
Pridolian as well as in the Lower Devonian.