Fault-related fold kinematics recorded by terrestrial growth strata, Sant Llorenc de Morunys, Pyrenees Mountains, NE Spain

摘要

Foreland basin growth strata are ideal recorders of deformation rates and kinematics in tectonically active regions. This study develops a high-resolution chronostratigraphic age model to determine folding rates in the Eocene-Oligocene terrestrial growth strata of the Berga Conglomerate Group, NE Spain. The Berga Conglomerate Group was sampled for rock magnetic, magnetostratigraphic, and magnetic susceptibility (chi) cyclostratigraphy analyses. Analysis of rock magnetic measurements indicate a mixed mineral assemblage with both paramagnetic and ferromagnetic minerals. A new magnetic reversal stratigraphy constrains the time frame of folding and is in agreement with previous interpretations. Time series analysis of chi variations show statistically significant power at expected orbital frequencies and provides precession-scale (20 kyr) temporal resolution. Strain measurements including anisotropy of magnetic susceptibility (AMS) fabrics and bedding plane strain worm burrow distortion are consistent with fixed hinge, flexural folding kinematics. Fault-related folding was modeled using chi cyclostratigraphy timing and strain measurement kinematic constraints. The onset of folding was at 33.85 Ma and the end of deformation is less constrained but is younger than 31.06 Ma. Deformation and sediment accumulation rates are unsteady at 20 kyr time scales but appear artificially steady at polarity chron time scales. (C) 2016 Elsevier Ltd. All rights reserved.