| Folds are commonly accompanied by thrusts in deformed low- to medium-grade sedimentary belts. The Acadian fold belt (AFB) of the Meguma Group (comprising the slatey Halifax and sandy Goldenville formations) in east mainland Nova Scotia lacks thrusts. To address the question of why folds predominate in the AFB, an applied geographic information systems-geophysical approach was employed to establish and constrain the basic geometry of the folds by the construction of balanced cross-sections.; The balanced cross-sections reveal two orders of folding. The 1 st order folds are large-scale, 11 to 18 km wavelength, steep limbed anticlinoria and synclinoria with strong VG anomalies highlight the boundaries between 1st order folds. The 2nd order folds are 4 to 6 km wavelength anticlines and synclines that include cylindrical folds with periclinal fold tips. Periclinal fold tips range in plunge from 1 to 22°. Buckle shortening is 35%. Calculated detachment depths increase from south to north, approximately 6 km along the coast to between 10 and 14 km inland.; The folds are interpreted to have developed in a thick competent multilayer (Goldenville Formation) embedded in an incompetent medium with wavelengths determined both by gravity and mechanical properties of the multilayer. The incompetent embedding medium comprises the Halifax Formation above and a weak unit, perhaps less competent Goldenville Formation below, the competent, multilayered Goldenville Formation. (Abstract shortened by UMI.)... |
