Lithostratigraphy and provenance of the Neoarchean McKellar Harbour Sequence, Superior Province, Ontario, Canada

Abstract

The McKellar Harbour Sequence is located on the shore of Lake Superior approximately 40 km west of the town of Marathon, Ontario. The Sequence was examined in detail through stratigraphic and geochemical investigations in order to determine the depositional environment and provenance of these rocks. Four subsequences were identified in the McKellar Harbour Sequence, consistent with the facies associated with a distal submarine ramp environment. The Sequence shows thickening and coarsening upward trends, indicative of progradation of the ramp onto the basin floor. This indicates that the rocks of the McKellar Harbour Sequence are the distal equivalents of the proximal submarine ramp facies identified in the Beardmore-Geraldton and Quetico terranes to the north of the study area. Sedimentary strata from other potential source regions did not exhibit the characteristic features of a submarine ramp, and were likely deposited through different processes. Insufficient data were collected to determine the depositional environment for these units. Geochemical analyses indicate that the rocks of the McKellar Harbour Sequence have immobile element chemistry that is very similar to that of the Beardmore-Geraldton and Quetico terranes, and that a continuum of deposition from north to south is present. Sediments generated in the Beardmore-Geraldton terrane were transported to small basins associated with the Schreiber-Hemlo volcanic island system by a submarine ramp.