Tectonism and an Upper Silurian Ramp-Prodelta-Rimmed Shelf Succession from Arctic Canada: An Intracratonic Product of Caledonian Compression

Jeffrey J. Packard, Owen A. Dixon

Late Silurian and Early Devonian shelf architecture in the vicinity of Cornwallis Island in the central Arctic Archipelago was largely determined by a series of diastrophic events that are collectively termed the Cornwallis disturbance. The disturbance affected a fault-bounded, basement-cored, intracratonic crustal segment, the Boothia Uplift, which forms a northerly trending feature some 1,000 km long and 80 to 150 km wide oriented normal to the tectonodepositional strike of both the Franklinian and younger Sverdrup basins.

Marine deposition within the vicinity of the uplift can be divided into five phases corresponding to changes in the relative intensity of penecontemporaneous regional tectonism. Phase 1 (late Ludlovian) is a quiescent stage, typified by carbonate ramp sedimentation. The Douro Ramp was a homoclinal ramp that bordered a low-energy, turbid, meromict sea. Phase 2 represents the termination of the stable carbonate ramp and the onset of syntectonic sedimentation. Phase 2 (late Ludlovian) is represented in the rock record by the precipitous and near-simultaneous occurrence of stacked hardgrounds, slope failure phenomena, ox-redox banding, tempestites with significant siliciclastic content, and abrupt shallowing of biofacies. Phase 3 (latest Ludlovian) corresponds to a period of continental w sting and deltaic sedimentation as the newly emergent terrane of the Boothia Uplift shed its detritus northward to form the Hotham clinoform. Phase 4 (latest Ludlovian to earliest Lochkovian) is represented by the Barlow Inlet Platform, an attached rimmed shelf with an accretionary shelf margin. The platform sequence is punctuated by a number (7 minimum) of major forestepping and backstepping events that are attributed to episodic movement of the Boothia Uplift. Phase 5 is the denouement of carbonate sedimentation in the study area. The Barlow Inlet platform initially became an emergent feature of low relief (early Lochkovian) and then was partially exhumed during a period of intense uplift that witnessed alluvial fan sedimentation associated with major high-relief fault scarps (mid to l te Lochkovian).

Activity that formed the Boothia Uplift occurred contemporaneously with the late sinistral transpressive phase of the Caledonian orogeny. Uplifts appear to have formed where structural trends in the basement were northerly and presumably favored response to gentle, west-directed compression.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.