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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 68 (1984)

Issue: 4. (April)

First Page: 449

Last Page: 449

Title: Oblique-Slip Sedimentation and Deformation in Nonacho Basin (Early Proterozoic), Northwest Territories, Canada: ABSTRACT

Author(s): Lawrence B. Aspler, J. A. Donaldson

Abstract:

The Nonacho basin shares several traits with molassoid basins formed in oblique-slip settings: (1) great thicknesses (about 9 km, 6 mi) of siliciclastic sediments deposited in alluvial fan, fan-delta, braided stream, beach, deltaic, and lacustrine environments; (2) synsedimentary faults which activated nearby sources; (3) rapid sedimentation and subsidence; (4) telescoped facies transitions, particularly adjacent to active faults; (5) extremely variable thicknesses of lithostratigraphic units; (6) diachronous sedimentation resulting from the migration of source areas and sites of sedimentation along deformation fronts; (7) mobility of deposition and deformation such that early sediments were uplifted, cannibalized, and redeposited; (8) paleocurrents directed basinward nea basin margins, and longitudinally in axial regions; (9) lower greenschist facies metamorphism; (10) paucity of volcanic rocks; and (11) complicated structural geometries. However, these features alone are not diagnostic of oblique-slip origin; all are compatible with rift, aulacogen, impactogen, retroarc, peripheral, intramontane, and broken foreland settings. More reliable indicators of an oblique-slip tectonic setting for the Nonacho basin are: (1) anastomosing pattern of near-vertical, en echelon faults which delineate rhomb-, wedge-, and rectangular-shaped semi-independent subbasins and basement uplifts; (2) stretching lineations of shallow to moderate plunge along shear zones; (3) folds and near-vertical penetrative fabrics, related to shear zones, but at angles of 20°-30° to these zones. The Nonacho basin fill is interpreted as a foreland molasse of the Trans-Hudson orogene. Deposition and deformation probably occurred in response to convergence accommodated by oblique slip, analogous to the Tarim and Tsaidam basins of China, which developed in the late stages of India-Eurasia collision, north of the Tibetan Plateau.

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