Coordinated displacement on adjacent faults using growth strata at 104-5 year timescales; Catalan Coastal Range, Spain

Abstract

Samples from the Catalan Coastal Ranges, NE Spain, in the wedge-top Mora basin and in the eastern Ebro foreland basin, allow for high-resolution dating of mountain belt formation. Bulk low field magnetic susceptibility data and magnetic polarity stratigraphy, correlated to the GPTS, provide the stratigraphic ages and the rates of accumulation in the synorogenic stratigraphy. The growth strata are part of the proximal Horta-Gandesa alluvial system of late Eocene-Oligocene age. The synorogenic stratigraphy is exposed along the abandoned Pinell de Bray railroad grade, providing near continuous exposures near the towns of Bot and Horta de Sant Joan, Spain. The growth strata were shed by coarse, transverse, braided streams as alluvial fans coincident with thrust belt formation. The recovered magnetic susceptibility data were tuned to orbital mechanics, which are known to result in long term environmental varibilty in Earth’s climate. The magnetic susceptibility data are used to correlate time between the interpreted magnetic polarity chrons on adjacent structures and to provide insights into deformation mechanics and the feedbacks between deformation, landscape evolution, and synorogenic sedimentation. The recovered astrochronology records significant (with respect to robust red noise models) vertical aggregational cycles at 11-15m, 65-85m, and ~270m. The multihierarchical growth strata ages are used to deduce coordinated fault activity and are interpreted to result from Paleogene precessional, obliquity and eccentricity cyclicity forcing.