The very high spatial resolution and stereo capability of GeoEye-1 images were utilized to map the geology of a part of the western Neoproterozoic Minto Inlier on Victoria Island. To optimize the results of predictive mapping, a LANDSAT-7 image together with a SPOT-5 image were also used in concert with the GeoEye-1 images. The predictive bedrock geology map, interpreted based on 3D stereo visualization, presents much more detailed geological information compared to the existing 1:500,000 scale geological map of the area. The high spatial and moderate spectral resolution of GeoEye images allowed us to distinguish a black shale unit (black shale member), and resolve subtle spectral and textural differences between massive stromatolitic dolostone and dolostone containing fine-grained interlayers in an upper carbonate member. As well, an important distinction could be made between Proterozoic sedimentary strata and unconformably overlying interlayered sandstone and carbonate rocks of Cambro-Ordovician age. The SWIR bands in the LANDSAT and SPOT images proved to be very useful in identifying gabbro sills. A geological map, based on field work, was used to evaluate the remote predictive map. Comparison of the predictive map with the field map shows that the two maps look similar in terms of the regional distribution of the lithological units; however, there are discrepancies between the two maps, especially in areas in which the bedrock is covered by glacial sediments and/or other overburden materials. The spectral similarity between different stratigraphic units comprising similar rock types, also contributed to differences between the predictive map and the field map.
This map and the related geodatabase illustrate the bedrock geology of central and northeastern Victoria Island, Stefansson Island, and western Prince of Wales Island. Major features of the area include inliers of Neoarchean basement granitoid rocks; clastic rock-dominated sections associated with the late Paleoproterozoic Kilohigok Basin, and Mesoproterozoic Elu Basin; extensive Meso- and Neoproterozoic strata of Amundsen Basin, diabase sills, and extrusive basaltic rocks related to the Franklin Large Igneous Province (ca. 723 Ma) and unconformable Cambrian to Devonian strata of Arctic Platform.
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Isopachs of Huronian strata of the Elliot and Hough Lake groups in the southern part of the Cobalt Basin can be used to define the geometry of a 4 km wide valley system that directly influenced the location of gravel-bed rivers bearing detrital gold and auriferous pyrite in the Mississagi Formation. Distribution and thickness of these and underlying formations can be directly linked to initial valley formation parallel to existing north-south-oriented faults in the Archean basement. Thickness distributions were directly influenced by active subsidence associated with transverse, east-south-east (ESE)-oriented, normal faults, related to extension along the Huronian transform-rift margin further south. Strata underlying the Mississagi Formation were largely removed by erosion in the northern part of the paleovalley system, but thickened and then thinned south of the ESE faults. Pyrite and detrital gold in the Mississagi Formation may have been concentrated from reworking of coarse clastic rocks of the Matinenda and Ramsay Lake formations, along with significant contributions from erosion of proximal Archean basement within 3–5 km of the preserved basin margins. There is strong evidence to suggest that stream flow was initially concentrated in three main structurally influenced valley systems in the north, with one lateral tributary in the south-eastern part of the basin. The fluvial systems merged, and thickened, south of the Tee Lake fault, possibly reflecting trans-tensional influences on the basin margin faults.
Geochemical and geochronological data from the Pinguicula Group and unit PR1 of the lower Fifteenmile Group (Yukon, Canada) provide information on sediment provenance and timing of break-up of supercontinent Columbia and seaway development on Laurentia’s northwestern margin. The older unit PR1, in the Coal Creek inlier, has a near-unimodal detrital zircon population with an age of 1499 ± 3 Ma. The Pinguicula Group detrital zircon data, in the Wernecke and Hart River inliers, display a polymodal detrital zircon population with a maximum age of <1322 ± 23 Ma. Using detrital zircon signatures, Sm–Nd isotopic data, and C-isotopic signatures, lithostratigraphic correlations between the Pinguicula Group in the Wernecke and Hart River inliers are confirmed, whereas the Pinguicula Group and unit PR1 are no longer considered correlative. The zircon population in unit PR1 requires a proximal source, but sources of this age are not known in western Laurentia. Based on detrital zircon and Sm–Nd data, sediment in unit PR1 was derived from the Mt. Isa inlier in northeastern Australia sometime after 1460 Ma. Unit PR1 correlates with older Mesoproterozoic successions, including the Belt-Purcell, that were deposited during break-up of supercontinent Columbia, and contain sediment from Australia and the Mawson continent. Mesoproterozoic successions deposited after 1.45 Ga, including the Missoula Group, lack North American Magmatic Gap (NAMG)-aged zircon and instead record sediment provenance from southern Laurentia, as north Australia and the Mawson continent rifted from Laurentia’s western margin. The Pinguicula Group has few NAMG-aged grains that were probably recycled from older Mesoproterozoic basins.
Fluvial sandstone in the Kilohigok and Elu basins of western Nunavut record deposition related to the amalgamation and tenure of the Nuna supercontinent. The ca. 1.9 Ga Burnside River Formation was sourced by erosional unroofing of the nearly coeval Thelon Orogen, about 250 km away, in a regime of crustal flexure. This proximally sourced sandstone contains abundant clustered channel forms that point to high-magnitude discharge and sediment yield in weakly mobile channels. By comparison, the ca. 1.6 Ga Ellice Formation was sourced by the erosional unroofing of the ca. 1.8 Ga Trans-Hudson Orogen, about 1000 km away, in a geodynamic regime of thermally driven sagging. The distally sourced Ellice Formation contains some rare and nonclustered channel forms that point to lesser discharge and sediment yield in mobile channels. Provenance analysis and plate models support links between the fluvial style of the Burnside River and Ellice formations and orogenic unroofing facilitated by Hadley-cell atmospheric circulation at tropical paleolatitudes.
Lacking evidence for fluvial lateral-accretion elements in early Palaeozoic systems has been ascribed to an absence of binding by rooted vegetation on subaerial landscapes. Transposing this thesis to earlier geological times, it has been proposed that, likewise, Precambrian landscapes could not have sustained highly sinuous fluvial networks. This paradigm has been hardly ever tested for the Proterozoic, a shortcoming addressed here through review of selected outcrop data and remote sensing of modern sinuous channel-flow configurations. Five sedimentary rock units deposited on Laurentia between 1.6 to 0.7 Ga record diverse palaeogeographic and tectonic settings and yield evidence of lateral accretion and planform sinuosity in fluvial channels over a full range of developmental stages. In the absence of vegetation, multiple processes interacted at craton to channel-reach scales, setting conditions favourable for self-sustained lateral accretion and thus sinuosity. Discharge modulation in perennial channels is interpreted to have had an overriding role, owing to craton-scale catchments capable of sustaining year-round flows or favourable climate settings. Steady sediment supply and local channel-bank strengthening limited braiding, allowing for narrow hydraulic profiles with flow configurations favourable to lateral accretion. Less than 15% of current literature on Proterozoic fluvial rocks reports reliable directional data on palaeoflows and stratal accretion, a bias that undermines literature compilations aimed at gauging the relevance or insignificance of pre-vegetation lateral accretion. Fluvial deposits aggraded on unvegetated landmasses prior to the late Ordovician can only be assessed when comprehensive information on palaeoflow and bar accretion becomes available. The authors thus underline that a lack of evidence for early Palaeozoic lateral-accretion sets should not be used to support the inference that meandering fluvial planforms were a rare occurrence in earlier geological times.
