Transverse Zones in the Eastern Cordillera (Colombia): An example in the Zipaquira Anticline

Abstract:

Lateral connectors are expressed in map view by along-strike terminations of thrust faults and ramp anticlines; by curves and offsets in strike; and by along-strike changes in angle and direction of plunge, dip of fold limbs, direction of vergence, stratigraphic level of detachment, and structural style. Such lateral connectors could be formed from reactivated transform faults, transverse faults or lateral ramps. The Zipaquira Anticline (ZA) is a salt-cored structure, with a NE-SW axial axis direction, a clear defined map-view curvature. The Neusa Transverse Zone (NTZ) controls the kinematicof faults and folds. The Zipaquirá Transverse Zone (ZTZ) is located to the southern of the ZA. This transverse zone is a key feature in the area, controlling the ZA and allowing the ascend of diapirs and salt sheets to shallow deeps. Our study was focused on Cretaceous marine sediments and Cenozoic transitional to continental sedimentary sequence around the ZA. 224 oriented cores were collected using a gas portable drill. At each site we collected 10 cores, spaced in order to try to average out secular variation. All samples were oriented using a magnetic compass, corrected to account for the local magnetic field declination. Cores were cut into standard cylindrical specimens and magnetic fabric, rock magnetic and paleomagnetic measurements were done in the shielded room of the paleomagnetic laboratory of in the IAG in the Sao Paulo University. We measured the low-field (AMS) in a Kappabridge (MFK1-FA, AGICO). All samples were thermally demagnetized up to 680°C by a shielded oven, and the natural remanent magnetization (NRM) of the specimens was measured. Magnetic mineralogy analyses were carried out to identify and characterize the main magnetic carriers. The ZA is an important example of natural connection between multiple factors controlling deformation and geological evolution. Interaction between salt, transverse zones and folding, the ZA could be considered as a scale model for the Eastern Cordillera. Our goal is related the ZA and the transverse zones using Anisotropy of Magnetic Susceptibility (AMS) and paleomagnetism to unraveal the kinematic evolution of the anticline and the temporal relationship between the transverse zones and the ZA.