Magnetic mineralogy of Jurassic rocks in the Eastern Cordillera, Colombia

We report magnetic mineralogy from Triassic to Lower Cretaceous of volcano-sedimentary and continental sedimentary sequences in the Santander Massif and the Eastern Cordillera of Colombia. A total of 44 samples were distributed in the Norean and Jordan formations, and the Giron Group located in the Santander Massif and west flank of the Eastern Cordillera and the Palermo, Montebel, and Russia formations located in the Arcabuco Anticlinorium in the axial zone of the Eastern Cordillera. Three experiments were carried out, the isothermal remanent magnetization, thermal demagnetization of the three components of isothermal remanent magnetization, and the temperature versus magnetic susceptibility thermomagnetic curves. The results show units from the Triassic to the Middle Jurassic are characterized by the contribution of detrital magnetite and locally the contribution of pyrrhotite in the Montebel Formation. The Upper Jurassic to Lower Cretaceous, Giron Group is characterized by a magnetic mineralogy dominated by ilmenite-hematite and the absence of detrital magnetite. Compositional differences in detrital magnetite could be associated with the distance from the source area, climate, and the velocity of the flow.

Automated summary

We present a study on the magnetic mineralogy of Triassic to Lower Cretaceous volcano-sedimentary and continental sedimentary sequences from the Santander Massif and Eastern Cordillera in Colombia. Samples from the Norean and Jordan formations, Giron Group, Palermo, Montebel, and Russia formations were analyzed using three experiments. Results indicate that the Triassic to Middle Jurassic units are characterized by detrital magnetite with local contributions of pyrrhotite, while the Upper Jurassic to Lower Cretaceous Giron Group is dominated by ilmenite-hematite mineralogy without detrital magnetite. Differences in detrital magnetite composition may be influenced by source area distance, climate, and flow velocity.