Dating synfolding remagnetization: Approach and field application (central Sierra Madre Oriental, Mexico)

Growth of magnetite has been variably linked to fluid-bearing events or clay diagenesis, and the development of a chemical remagnetization as a result of such events. In this study we examine remagnetized carbonate rocks from the central Sierra Madre Oriental (the Mexican fold-thrust belt) in order to develop a method for dating synfolding remagnetizations. By combining 40 Ar/ 39 Ar deformation ages with new paleomagnetic results, we present a quantitative method for absolute dating of synfolding remagnetization. We find that the history of the central Sierra Madre Oriental involved two separate remagnetization events in our study area; synfolding remanence acquisition ca. 77 Ma (Late Cretaceous) in the Zimapan Basin and a younger synfolding remagnetization event ca. 44 Ma (mid-Eocene) in the Tampico-Misantla Basin. The growth of magnetite leading to chemical remagnetization detected in these limestones is interpreted as the result of rock interactions with an Fe-bearing fluid.