Leandro C. Gallo, Renata N. Tomezzoli, Alejandra Dalenz Farjat, Roberto M. Hernández
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Latinmag Letters, Volume 6, Special Issue (2016), B14, 1-6. Proceedings São Paulo, Brasil
Se realizó un estudio magnetoestratigráfico en sedimentitas del Paleozoico Superior de la Cuenca de Tarija. Para tal fin, fue muestreada a escala decamétrica una sección continua de alrededor de 800 m que incluyen sedimentos glaci-lacustres de la Formación San Telmo (Grupo Mandiyutí superior) y la super-secuencia de estratos rojos del Grupo Cuevo. El análisis paleomangnético revela una componente de gran estabilidad a temperaturas mayores a 600º C, esta componente se interpreta como una magnetización remanente característica (MRCa), cuyo mineral portador es hematita que fue adquirida con anterioridad al plegamiento, sobre la base de un test de plegamiento (Enkin, 2003). Se obtuvo una posición paleopolar levemente diferente después de corregir el error de inclinación por el método de Elongación-Inclinación (Tauxe, Kent, 2004). La posición computada luego de la corrección (60.8ºS 349º E; N =16; α95 =3.9; k=16) es consistente con las direcciones del Carbonífero Superior – Pérmico Inferior de Gondwana. La presencia de magnetizaciones normales hacia el techo de la columna indica que su depositación ocurrió con posterioridad al Supercron de Polaridad Reversa Kiaman, indicando que la base de la Formación Vitiacua es de edad Guadalupiana.
We carried out a magnetostratigraphic and anisotropy of magnetic susceptibility study of late Paleozoic
sediments of the Tarija Basin. With this aim, we sampled at decametric scale a continuous section of
about 800 m including glaci-lacustrine sediments of the San Telmo Formation (upper Mandiyuti Group)
and a regressive red bed megasequence (Cuevo Supercuence). Paleomangnétic analysis reveals a highly
stable component to temperatures above 600° C, this component is interpreted as a characteristic remanent magnetization (ChRM). Hematite is the likely carrier of this magnetic component and was acquired prior to folding, on the basis of a fold-test (Enkin, 2003). A slightly different average inclination, and thus paleomagnetic pole position, is obtained by correcting the inclination shallowing error by the Elongation–Inclination method (Tauxe, Kent 2004). The calculated position after correction (60.8ºS 349th E; N = 16; α95 = 3.9, k = 16) is consistent with the directions of the upper Carboniferous - lower Permian Gondwana APWP. The presence of both normal and reversed polarity zones to the top of the column indicate deposition after the end of the Kiaman Superchron. Our results indicate a Guadalupian age for the base of the Vitiacua Formation.
sediments of the Tarija Basin. With this aim, we sampled at decametric scale a continuous section of
about 800 m including glaci-lacustrine sediments of the San Telmo Formation (upper Mandiyuti Group)
and a regressive red bed megasequence (Cuevo Supercuence). Paleomangnétic analysis reveals a highly
stable component to temperatures above 600° C, this component is interpreted as a characteristic remanent magnetization (ChRM). Hematite is the likely carrier of this magnetic component and was acquired prior to folding, on the basis of a fold-test (Enkin, 2003). A slightly different average inclination, and thus paleomagnetic pole position, is obtained by correcting the inclination shallowing error by the Elongation–Inclination method (Tauxe, Kent 2004). The calculated position after correction (60.8ºS 349th E; N = 16; α95 = 3.9, k = 16) is consistent with the directions of the upper Carboniferous - lower Permian Gondwana APWP. The presence of both normal and reversed polarity zones to the top of the column indicate deposition after the end of the Kiaman Superchron. Our results indicate a Guadalupian age for the base of the Vitiacua Formation.
http://www.geofisica.unam.mx/LatinmagLetters/LL16-01-SP/B/B14.pdf
