IGEBA   23946
INSTITUTO DE GEOCIENCIAS BASICAS, APLICADAS Y AMBIENTALES DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
PALEOMAGNETISM OF JURASSIC AND LOWER CRETACEOUS ROCKS IN THE WESTERN FLANK OF THE PERIJA RANGE; CONSTRAINTS FOR JURASSIC PALEOGEOGRAPHY AND ROTATIONS
Autor/es:
NOVA, GIOVANNI; MONTAÑO, PAOLA CATALINA; BAYONA, GERMÁN; RAPALINI, AUGUSTO E.; MONTES, CAMILO; SILVA, CESAR
Reunión:
Congreso; 108th Annual Meeting Geological Society of America; 2012
Institución organizadora:
Geological Society of America
Resumen:
PALEOMAGNETISM
OF JURASSIC AND LOWER CRETACEOUS ROCKS IN THE WESTERN FLANK OF THE
PERIJA RANGE; CONSTRAINTS FOR JURASSIC PALEOGEOGRAPHY AND ROTATIONS
NOVA, Giovanny1, MONTAÑO, Paola Catalina1, BAYONA, Germán1, RAPALINI, Augusto.E.2, MONTES, Camilo3, and SILVA, Cesar1,
(1) Corporación Geológica ARES, Calle 44 A # 53-96, Bogotá, Colombia,
gionovar@hotmail.com, (2) Instituto de Geofísica Daniel A. Valencio
(INGEODAV), Facultad de Ciencias Exactas y Naturales, Universidad de
Buenos Aires, Pabellón 2, Ciudad Universitaria, Buenos Aires, 1428,
Argentina, (3) Geosciences, Universidad de Los Andes, Bogota, Colombia
In
order to establish the origin and evolution of the Perija range (PR),
and its relation with accreted terranes in northwestern South America, a
paleomagnetic study of 15 sites was carried out in the Jurassic La
Quinta Formation and lower Cretaceous Río Negro Formation of the
southwestern flank of the PR. Characteristic components with
northeastward directions were isolated in the Rio Negro Formation (D=
38.5 I=7.4 k=13.2 a95=15.8 N=6) and La Quinta Formation (D= 31.6 I=19
k=30.94 a95=11 N=7). Normal and reversal directions were documented in
La Quinta Formation, and the mean inclination of La Quinta is higher
than of the Rio Negro Formation.
The comparison of these directions with middle Jurassic and lower
Cretaceous directions calculated for a nearby site in the craton
(4N72W) documents different magnitude of clockwise rotation. For La
Quinta Formation the magnitude is 41.7° ± 16.3, while for the Rio Negro
Formation is 28,2° ± 16.4. Comparison of the Jurassic mean direction
with the reported in the eastern flank of the PR for only Jurassic rocks
(Gose et al. 2003; D= 48.1 I=26.8; clockwise rotation 44.7°±14.2° N=1)
indicate similar magnitude of rotations but different inclination
values. Comparison between Jurassic directions of the PR with the
Jurassic directions from the Santa Marta massif (Bayona et al. 2010; D=
20.4 I=-18.2; clockwise rotation 17°± 12.8°), indicate a higher
magnitude of clockwise rotation for the PR, but different inclinations;
the Santa Marta massif inclinations are negative, whereas in the PR are
positive. The difference in magnitude of inclination for both middle
Jurassic units could be explained as a result of magnetization at
different paleolatitudinal position of those blocks.
More sites in Jurassic and lower Cretaceous rocks are needed in
the northern segment of the PR to document whether the scale of
vertical-axis rotation is regional or is associated to local structures,
and better constrain the paleogeographic position of the PR for
Jurassic and early Cretaceous time.