INVESTIGADORES
DAVILA Federico Miguel
artículos
Título:
Dynamics of deformation and sedimentation in the northern Sierras Pampeanas: An integrated study of the Neogene Fiambalá basin, NW Argentina (DISCUSSION)
Autor/es:
DAVILA, F.M.
Revista:
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
Editorial:
GEOLOGICAL SOC AMER, INC
Referencias:
Año: 2010 vol. 122 p. 946 - 949
ISSN:
0016-7606
Resumen:
In a recent contribution to the Geological Society
of America Bulletin, Carrapa et al. (2008)
provided an interesting geochronological and
thermochronological database for the Fiambalá
Basin, northern end of the Sierras Pampeanas,
which, together with stratigraphic, sedimentological
and structural data, led them to interpret
a late MiocenePliocene foreland reorganization
from a simple scenario (e.g., DeCelles and
Giles, 1996) to settings dominated by intermontane
basement thrusting. They associated
this reorganization with the beginning of fl at
subduction, which would have been coeval
(according to Carrapa et al., 2008) with broken
foreland stages in the Bermejo Basin (>400 km
south). One of the most crucial issues that
Carrapa et al. (2008, p. 15181543) address (in
their words) is the structural and sedimentary
behavior of broken forelands and their relationships
with large-scale plate-tectonic processes
such as fl at-slab subduction that can contribute
to a better understanding of the transition
from unbroken foreland (thin-skinned) to broken
foreland (thick-skinned) styles of deformation
and related sedimentation. However,
for some reason, they did not discuss the entire
Andean stratigraphy of the area, superbly
exposed much less than 50 km southward
and 100 km northward of their study region
(in central Famatina and Southern Puna, respectively;
see Fig. 1). These two regions are
evidently much closer than the Bermejo Basin
exposures (see Jordan et al., 2001), which were
used as a key correlation. The Bermejo Basin
is located at ~31°S, i.e., ~400 km southward of
Fiambalá (Fig. 1).
Although I do agree that the entire extent of
the Sierras Pampeanas shows evidences of basement-
thrusting tectonics during the late Miocene
to Pliocene and even during the Quater nary
(already demonstrated previously; e.g., Jordan
and Allmendinger, 1986; Ramos et al., 2002;
among others), there are sources that indicate
the foreland partitioning would have begun earlier.
Particularly, I disagree with: (1) the timing
of transformation from simple fl exural stages
to broken foreland scenarios and (2) their interpretation
about a synchronous slab shallowing
at ca. 6 Ma.
This discussion is divided into four lines of
reasoning: mapping and stratigraphy of Tertiary
sequences in Famatina and Southern Puna; timing
of basement thrusting in boundary regions;
thermochronology; and evidences of fl at subduction
between 29°S and 26°S.