INVESTIGADORES
RICHIANO Sebastian Miguel
artículos
Título:
TSUNAMI VS STORM ORIGIN FOR SHELL BED DEPOSITS IN A LAGOON ENVIROMENT: AN EXAMPLE FROM THE UPPER CRETACEOUS OF SOUTHERN PATAGONIA, ARGENTINA
Autor/es:
AUGUSTO N. VARELA, SEBASTIÁN RICHIANO & DANIEL G. POIRÉ
Revista:
Latin American journal of Sedimentology and Basin Analysis
Editorial:
Asociación Argentina de Sedimentología
Referencias:
Año: 2011 vol. 18 p. 63 - 85
ISSN:
1669 7316
Resumen:
The criteria by which the deposits of tsunamis are distiguished from
other deposits, including storm surges, have been controversial for more than 10
years. The Mata Amarilla Formation of the lower Upper Cretaceous of Southern
Patagonia has excellent outcrops that in its lower section, sedimentary and
taphonomic characteristics suggest a tsunami origin. This paper presents details
of these aspects, as well as a model of temporal stages that led to their deposition
within a lagoon. The sediments are composed of alternating white sandstones and
mudstones, with interbedded bioclastic accumulations in the lower section. The
depositional environment was characterised by a lagoon bounded by shallow marine
bars. These fine-grained sediments are sporadically interrupted by tsunami events
represented by coquinas, bioclastic sands and shell pavements with allochthonous
and autochthonous mollusk associations from freshwater and marine habitats. Some
areas of the lagoon became exposed, thus enabling the development of vegetation on
the substrate and pedogenic processes. Subsequently, a forced regression occurred
when a fluvial system invaded the lagoon area, representing the beginning of the
deposition of the middle section of the Mata Amarilla Formation.