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Glacial Erosion of Bedrock and Ice Flow History in the Kivalliq Region
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 Geological Survey of Canada
Natural Resources Canada > Earth Sciences Sector > Geological Survey of Canada > Surficial Geology
Glacial Erosion of Bedrock and Ice Flow History in the Kivalliq Region, Nunavut, Canada
Multi-directional Indicators

Bedrock outcrops in the region often display two or more sets of striations having distinct trends. Opposing directions of ice flow are found near and under the area of the Keewatin Ice Divide. There, NNW striated surfaces are preserved on the south sides of small bedrock islands and rocky points while opposite SE to ESE striations dominate the north sides of the same outcrops. Cross-cutting striations record separate ice flows resulting from shifts in ice divides during a single glaciation, or from separate glacial events.

Multi-directional indicator Photo Description
Grooves and striations NE of Copperneedle Esker
Grooves and striations NE of Copperneedle Esker
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Deep, straight grooves and striations oriented SE (1) were observed in mafic volcanic rock in the SW extremity of the Tavani map sheet (55K). Well defined rat tails parallel to these grooves indicate a SE ward direction of ice flow. A second set of deep and fine striations oriented SSE (2) occur in between the large grooves. This younger flow is oblique to the Copperneedle esker located less than 2 km from this site and reflects lateral movement of ice toward the esker ridge during deglaciation.
Opposing roches moutonnées in Thirty Mile Lake
Opposing roches moutonnées in Thirty Mile Lake
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Roches moutonnées indicating opposite directions of ice flow to the WNW and to the ESE occur on a small island in Thirty Mile Lake. The sense of ice flow was defined by crescentic fractures and rat tails on both sides of this composite landform. The age relationship could not be determined. The area is located on the axis of the Keewatin Ice Divide.
Mistake Bay
Mistake Bay
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Two sets of striations are preserved on a flat bedrock island along the emerging Hudson Bay coast near Whale Cove. Deep striae and crescentic fractures indicating ice flow towards the ESE (1) are preserved on the gentle lee-sides (west) surfaces striated to the SE (2). The SE flow dominates on the island and the older ESE flow is found only on the west sides of outcrops.
Corbett Inlet
Corbett Inlet
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Two sets of striations are preserved on a large island offshore from Pork Peninsula near Corbett Inlet. Deep striae and grooves indicating ice flow towards the SE (1) are preserved on the lee-side (north) of ESE ward striated surfaces (2) which dominate the outcrops in the area. This relationship is opposite to the one found in Mistake Bay to the south and is thought to reflect late glacial ice flow associated with changing ice front positions.
Thirty Mile Lake map area - SE
Thirty Mile Lake map area - SE
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In the SE part of the Thirty Mile Lake map area, the age relationship between two opposing movements cannot always be determined. Truncation lines (shown in green) are smoothed and both faces are protected relative to the other. The age relationship between the two events was better defined at another outcrop further south, indicating that the NNW flow (1) preceded the SE flow (2).
Yathkyed Lake outlet - Kazan River
Yathkyed Lake outlet - Kazan River
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Near the outlet of Yathkyed Lake along the Kazan River, ESE deep striae and roches moutonnées (2) dominate the outcrop. NW oriented striations and crescentic gouges (1) are preserved on the lee-side (south) of the main striated surfaces.
Thirty Mile Lake area
Thirty Mile Lake area
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Along the shores of Thirty Mile Lake, the ice flow record is particularly complex. Evidence for up to 5 directions of distinct ice flows can be preserved on a single outcrop. Age relationships can be difficult to determine at an individual site. Here, three movements are recorded on mafic volcanic rock. Age relationships have been determined by regional associations between parallel sets of striae.
Thirty Mile Lake map area - NW
Thirty Mile Lake map area - NW
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In the NW Thirty Mile Lake map area, ice flows are predominantly westward and northwestward. Here along the western shore of Princess Mary Lake, NNW deep striae (1) are preserved on the lee-side (west) of the dominant and most recent westerly flow (2). This relative chronology is similar to that recorded in the SE part of the lake where old NNW trending crag-and-tail landforms are preserved.
Yathkyed Lake area
Yathkyed Lake area
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Multi-faceted outcrops forming small trigonal pyramid islands are common in the Yathkyed Lake area. The pyramidal shape is the result of glacial erosion from three different ice flow directions. Two of the truncated surfaces are commonly well striated.

2005-11-17Important notices