INVESTIGADORES
CASELLI Alberto TomÁs
artículos
Título:
Paleolimnology evolution in rift basins: the Ischigualasto?Villa Unión Basin (Central-Western Argentina) during the Triassic.
Autor/es:
MANCUSO, A.; CASELLI A.T.,
Revista:
SEDIMENTARY GEOLOGY
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2012 vol. 275- p. 38 - 54
ISSN:
0037-0738
Resumen:
Extensional basins offer a high preservation potential for sedimentary and fossil records. Nonmarine rift basins
contain diverse environments, including fluvial and lacustrine. Lake deposits have long been recognized as significant
archives of the paleoenvironmental record. The Ischigualasto?VillaUnión Basin represents the only nearly
continuous continental Triassic record with up to 6000 mof alluvial, fluvial, and lacustrine deposits. The deep
lacustrine interval is known as the Los Rastros Formation and consists of several lacustrine?deltaic cycles. A detailed
facies analysis allowed the characterization of five facies associations and two types of cycles: (1) a
shoreline-dominated, progradational Type I cycle containing Facies association A (offshore lacustrine deposits)
and Facies association B (marginal palustrine deposits along the shoreline of the lake) or Facies association C (lacustrine
siliciclastic coastal deposits) and (2) a delta-dominated, progradational Type II cycle characterized by
Facies association A (offshore lacustrine and prodelta deposits), Facies association D (delta front deposits), and
Facies association E (delta plain deposits). The sedimentary evolution of the Chañares?Los Rastros sequence is
defined within this extensional setting as one depositional sequence with three system tracts (lowstand, transgressive,
and highstand system tract). Biotic, abiotic, and sedimentologic data allowed the interpretation of the
limnologic dynamics of the Los Rastros paleolake as a deep freshwater lake within a half-graben, exhibiting
meromixis, and showing a change frommoderate eutrophic conditionswith lowoxygen content to relatively oxygenated
oligotrophic conditions. The successive fluctuations recorded in lake level are considered in the sequence
stratigraphic framework of Bohacs et al. to reflect the relative balance of sediment and water input
versus accommodation in an overfilled lacustrine basin.