BREAKUP OF LIMESTONE BEDROCK BY FROST SHATTERING AND CHEMICAL-WEATHERING, EASTERN CANADIAN ARCTIC

This paper investigates the range of Holocene weathering features in Arctic carbonate terrain, and suggests mechanisms for their genesis. Both the bedrock macrostructure and microstructure are conducive to breakdown. Joints, weak beds, and vugs allow infiltration of water and provide sites for fracturing by volumetric expansion of water as it crystallizes into ice, either in open-system or closed-system environments, or by hydraulic freezeback processes. Hairline discontinuities along bedding planes and the silty clay texture of disaggregated products provide surfaces and capillaries that promote ice lensing and hydration weathering. Frost weathering produces extensive areas of broken pavement, block fields, and sorted circles. Slabby limestone is buckled upward to a height of 1.5 m along joint lines. Joint expansion and detachment of blocks from parent rock masses cause topples along cliff faces. Chemical reactions with atmospheric CO2, water, and limestone create solution pits on exposed surfaces, with precipitation of secondary carbonate below. Weathered bedrock joints are depleted in carbonates and enriched in iron oxide and clay minerals.