Abstract

During recession of continental ice of the Wisconsin stage a complex series of moraines and pitted plains was deposited on Cape Cod and adjacent portions of southeastern Massachusetts. Most notable are the Buzzards Bay moraine, extending in a northeast-southwest direction along the southeast shore of Buzzards Bay, and the Sandwich moraine, trending east-west and roughly parallel to the south shore of Cape Cod Bay. These were deposited during minor readvances of the lobate margin of the ice. The lithologic character of the transported stones reveals the direction from which the ice advanced and is distinctive for the two major lobes of ice. Along the shore north of the Sandwich moraine there are discontinuous bodies of till resting upon and surrounded by glacio-fluvial deposits. These constitute the Scorton moraine, deposited during the wastage of essentially stagnant ice, after retreat of the ice-front from the position marked by the Sandwich moraine. The Ellisville moraine, north of Buzzards Bay, represents a third type of recessional moraine, resulting from a temporary halt in the retreat of the margin of an active ice-lobe without readvance.

The Mashpee pitted plain occupies the angle between the Buzzards Bay and Sandwich moraines. It consists largely of sand and gravel spread by melt water across a land surface strewn with many large blocks of stagnant ice, left stranded beyond the continuous, lobate margin of the ice sheet, at a time when that margin was an appreciable distance north and northwest of the line now marked by those moraines and prior to the readvance of the ice responsible for their emplacement. An extraordinary number of large and deep kettle holes dot the surface of the gently sloping fan-shaped plain. Adjacent to some of them, clumps of till are embedded in the glacio-fluvial deposits. Many of the buried blocks of ice responsible for the kettle holes did not melt away until after the surface of the plain had been extensively furrowed by subaerial erosion and its western and northern margins had been overridden by active ice readvancing to form the bordering moraines.

Thousands of ventifacts are embedded in undisturbed glacial and glacio-fluvial deposits and in disturbed surficial zones throughout the region. All types of wind abrasion from incipient polishing and faceting to pronounced etching, deep fluting, or pitting are displayed. These stones were sculptured by sandblasting in a periglacial climate, both prior to the deposition of the till and during the construction of the glacio-fluvial deposits. Many of the wind-scoured surfaces were modified to greater or lesser extent by abrasion during glacial or glacio-fluvial transport. Thin weathered rims on some of the ventifacts apparently survived such transport but were truncated by wind-cut facets.

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