INGEOSUR   20376
INSTITUTO GEOLOGICO DEL SUR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Tectonic control on the evolution of Maastrichtian-Paleogene synorogenic sequences of the Fuegian thrust fold belt, Argentina
Autor/es:
PABLO TORRES CARBONELL; EDUARDO OLIVERO; LUIS DIMIERI
Lugar:
Mar del Plata
Reunión:
Congreso; Geosur 2010; 2010
Institución organizadora:
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale
Resumen:
A geological study of the Atlantic
coast of Tierra del Fuego between the punta Gruesa (54º 21
S; 66° 38.5
W) and the río Policarpo (54º 39 S; 65º 30 W) (Figure 1), and
other sectors of the Fuegian Andes, allowed us to define the stratigraphy and
sedimentology of synorogenic successions from the Austral basin, and their
genetic relations with the geometry and kinematics of the Fuegian thrust-fold
belt.
We define seven synorogenic
successions between the Maastrichtian and the Miocene, bounded by
unconformities: Maastrichtian-Danian (180 to 800 m), Paleocene (50 to 370 m), Ypresian (450 to 650 m), Lutetian (80 m), upper Lutetian-Priabonian
(1200 m),
Oligocene (1600 to 200 m)
and uppermost Oligocene-Miocene (200
m). These successions are composed of marine
sedimentites, mostly deposited by gravity flows bellow storm-wave base. The
paleocurrent directions and the petrography indicate sediment provenance areas
in the volcanic arc along the Pacific margin of the Andes, and in the core of
the Fuegian Andes, the former dominant between the Maastrichtian and the
Lutetian, and the latter since the late Lutetian.
The detailed mapping of the Fuegian
thrust fold belt structures allowed us to construct two balanced cross-sections
that depict their subsurface geometries. The southern cross-section shows main décollements
at the base of the Cretaceous and above the Maastrichtian-Danian, and
thrust-related folding of the Cretaceous-Miocene sedimentary cover. The total
shortening in that cross-section is of 41.8 km. The northern cross-section has a main
décollement at the base of the Paleocene-Ypresian rocks, and minor ones in
Bartonian-Priabonian levels. This section shows thrust-related folding of the
Paleocene-Miocene sedimentary cover, with a total shortening of 17.8 km.
By combining both cross sections,
estimating their location before the development of the Neogene Fagnano
transform system (Figure 2), six contractional stages are defined in relation
to the evolution of the thrust-fold belt, age-constrained by the
biostratigraphy of the synorogenic successions recognized: Df1 (Danian)
with layer parallel shortening and low percentages of shortening in the
foreland; Df2 (Ypresian) with development of thrust-related folding
in a forward thrust-sequence and shortenings between 7 and 18.8 km (21%); Df3
(Lutetian) with development of out-of-sequence structures and a shortening of 6.6 km (7.3%); Df4
and Df5 (Oligocene) related to backthrusting with a shortening of 13.6 km (15.2%); Df6LC
and Df6PG (latest Oligocene-Miocene), the last
contractional stages recorded in the eastern Fuegian thrust-fold belt, comprising
thrust-related folding within the belt with a shortening of 2.8 km (3.1%), and in the
leading edge of deformation with a shortening of 10.5 km (11.6%).