Abstract

Distinguishing subglacial till from glaciomarine drift or similar till-like sediments is critical to understanding the late Pleistocene history of the Puget Lowland of Washington. Comparison of void ratios and bulk densities of glacial till and till-like sediments whose origin may be established by other criteria indicates that there are measureable differences related to degree of compaction. These differences may be used to determine whether or not a till-like sediment was deposited beneath glacial ice. Since both void ratio and bulk density depend on particle-size distribution as well as on degree of compaction, differences between till and other till-like sediments are significant only if the samples have similar particle-size distributions.

Void ratios of till from the Puget Lowland are systematically lower than those of glaciomarine drift having similar lithologies, and bulk densities are higher. Although till-like sediments other than glaciomarine drift were not analyzed, the void ratio-bulk density methods should also apply to them.

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