Continental Asia SE of the Eastern Himalayan Syntaxis is a zone of SE-ward escape characterized since early Tertiarytimes by a clockwise rotation and crustal flow around the northern edge of India (Tapponnier et al., 1982). The SE-warddirected crustal drift is accommodated by major strike-slip shear zones, which bound elongated continental blocks. Inwestern Yunnan, from west to east three main tectonic blocks (called Tengchong, Baoshan, and Lanping–Simao blocks)are separated by the Gaoligong, Biluoxueshan–Chongshan, and Ailaoshan–Red River shear zones, respectively. TheCenozoic (late Paleogene-Neogene) tectonic deformation and kinematics along these major active strike-slip faults isfairly well understood (e.g. Zhang et al., 2010; 2012), whereas several uncertainties remain on the post-15 Ma and activedeformation.Here we report on new paleomagnetic data from Tengchong and Baoshan blocks, at both edges of the Gaoligong dextralstrike-slip fault zone. We paleomagnetically sampled 50 sites (ca. 500 oriented samples) from Jurassic-Tertiary red beds,Plio-Pleistocene lava flows and Pliocene whitish lacustrine silts located within a maximum distance of 20 km from thefault. Such distance is established considering that several studies demonstrated that shear-related rotations virtually endwithin 10–20 km from fault trace (Hernandez-Moreno et al., 2014 and references therein). The paleomagnetic sampleswere collected using a petrol-powered portable drill cooled by water and oriented in situ using the Sun (when possible)and a magnetic compass. Paleomagnetic measurements were carried out in the shielded room of the paleomagneticlaboratory of the Istituto Nazionale di Geofisica e Vulcanologia (INGV, Rome), using a 2G Enterprises DCsuperconductingquantum interference device cryogenic magnetometer. Although the measurements are still in progress,the results already available contribute significantly to understand the pattern of deformation and vertical axis rotationsalong the Gaoligong fault zone, and to assess quantitatively rigid block rotation vs. rotations due to fault displacementoccurring during Tertiary and Plio-Pleistocene times.
Paleomagnetism of the Gaoligong strike-slip fault zone (Yunnan, China): understanding block rotation pattern
Pellegrino A. G.;MANISCALCO, ROSANNA;
2016-01-01
Abstract
Continental Asia SE of the Eastern Himalayan Syntaxis is a zone of SE-ward escape characterized since early Tertiarytimes by a clockwise rotation and crustal flow around the northern edge of India (Tapponnier et al., 1982). The SE-warddirected crustal drift is accommodated by major strike-slip shear zones, which bound elongated continental blocks. Inwestern Yunnan, from west to east three main tectonic blocks (called Tengchong, Baoshan, and Lanping–Simao blocks)are separated by the Gaoligong, Biluoxueshan–Chongshan, and Ailaoshan–Red River shear zones, respectively. TheCenozoic (late Paleogene-Neogene) tectonic deformation and kinematics along these major active strike-slip faults isfairly well understood (e.g. Zhang et al., 2010; 2012), whereas several uncertainties remain on the post-15 Ma and activedeformation.Here we report on new paleomagnetic data from Tengchong and Baoshan blocks, at both edges of the Gaoligong dextralstrike-slip fault zone. We paleomagnetically sampled 50 sites (ca. 500 oriented samples) from Jurassic-Tertiary red beds,Plio-Pleistocene lava flows and Pliocene whitish lacustrine silts located within a maximum distance of 20 km from thefault. Such distance is established considering that several studies demonstrated that shear-related rotations virtually endwithin 10–20 km from fault trace (Hernandez-Moreno et al., 2014 and references therein). The paleomagnetic sampleswere collected using a petrol-powered portable drill cooled by water and oriented in situ using the Sun (when possible)and a magnetic compass. Paleomagnetic measurements were carried out in the shielded room of the paleomagneticlaboratory of the Istituto Nazionale di Geofisica e Vulcanologia (INGV, Rome), using a 2G Enterprises DCsuperconductingquantum interference device cryogenic magnetometer. Although the measurements are still in progress,the results already available contribute significantly to understand the pattern of deformation and vertical axis rotationsalong the Gaoligong fault zone, and to assess quantitatively rigid block rotation vs. rotations due to fault displacementoccurring during Tertiary and Plio-Pleistocene times.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
