Megablocks and Rafts

Abstract

The common occurrence of flat-lying glacial rafts or megablocks throughout glaciated plains was not appreciated until fairly recently (Stalker 1976; Sauer 1978; Ruszczyńska-Szenajch 1987). These megablocks are more-or-less horizontal, slightly deformed, and are often buried under or within thick drift giving little or no morphologic clue to their presence in the subsurface. They may, in fact, easily be mistaken for bedrock, if deep exposures or drilling logs are not available. In other cases, the megablocks form flat-topped buttes, small plateaus, or irregular hills, which have also been mistaken for bedrock outliers.