Reconnaissance paleomagnetic results from western Cuba

Abstract

A paleomagnetic study of Mesozoic rocks from the Sierra de Los Organos and Sierra del Rosario fold belts of western Cuba revealed postfolding magnetisation in diabases of the Late Jurassic El Sábalo Formation and carbonates of the middle Cretaceous Pons and the Late Cretaceous Carmita and Moreno formations. Steep components with inclinations of about 70° were isolated from all three formations; at the same time, postfolding shallow components were also found in a few samples of the Pons limestones. We rule out a possibility to account for these results by either horizontal movements or non-dipole field anomaly. Neither very appealing is a hypothesis of a post-remagnetization tilt of the entire region. All the components appear to be confined to a plane perpendicular to the main structural trends; we hypothesize that the remanences might have been distorted or re-aligned during deformation; this assumption, however, is far from being proven. In contrast, well-defined characteristic components were isolated from basalts of the Aptian-Albian Encrucijada ( D I = 247° 23° , K = 14, a 95 = 9.0°) and the Late Cretaceous Orozco ( D I = 228° 22° , K = 110, a 95 = 4.7) formations from the Bahia Honda zone in the north of western Cuba; the remanence in the Encrucijada Formation is shown to predate deformation. Mean inclinations in both formations match those in Cretaceous volcanics from central Cuba, and all the results show lower latitudes than expected from the reference data for the North American plate thus implying that volcanic domains of Cuba were displaced northward by about 1000 km prior to the Middle Eocene. Cretaceous declinations in western and central Cuba differ by about the same amount as the major structural trends of these two areas suggesting oroclinal bending of Cuba. At the same time, both areas are rotated counterclockwise with respect to North America thus implying movements on a broader scale.