Flexural-slip folding in the Meguma Group, Nova Scotia, Canada

Flexural-slip folding has been established for two anticlines in the Meguma Group, Nova Scotia. Flexural slip postdates the main Acadian episode of fl exural-flow fold growth and represents a late, brittle-ductile reactivation of the fold belt. Flexural-slip structures are dominated by bedding-parall el movement horizons, but include a linked system of frontal and lateral ra mps and conjugate movement horizons. Slip amount calculated from displaceme nt of discordant quartz veins, combined with vein spacing, indicates an ave rage local shear strain of approximately 0.5. However, because flexural-sli p occurred when the fold limbs were steep, the shear strain accounts for a small change in limb dip (4-8)degrees. Variation of slip amount with spacin g of movement horizons suggests progressive flexural slip was accommodated by continuous initiation of new movement horizons as well as continuing sli p on existing movement horizons. The presence of quartz veins along flexural-slip structures together with e vidence for ductile deformation coeval with flexural slip suggests that sli p episodes were fluid assisted and intermittent, separated by periods of du ctile deformation and build up of fluid pressure. Flexural-slip veins in th e Ovens Anticline are auriferous and a flexural slip model may be appropria te for other similar Meguma gold deposits. Thrust sheets, up to 10 m thick, occurring on a fold limb are interpreted t o have originated in flat box fold hinges and to have been placed onto the steep limbs of the chevron folds during the flexural slip episode. Thrustin g may have assisted the transformation of a box fold into a chevron. (C) 20 01 Elsevier Science Ltd. All rights reserved.