Waquoit Bay Reserve, Massachusetts

Geology

Waquoit Bay watershed, like all of Cape Cod, is a geologically young landform composed of glacial materials deposited on top of bedrock toward the end of the Wisconsinan Glacial Stage about 12,000 years ago. The Waquoit Bay watershed lies entirely within the Mashpee pitted outwash plain. Outwash plains were created by broad meltwater streams emanating from the melting glacier margins that carried sands and gravels that were once embedded within the glacial mass. The flowing meltwater streams size-sorted the drift materials depositing the heavier boulders and pebbles near the glacial margin and gravels and sands further away. The term "pitted" refers to the numerous kettle ponds dotting the landscape. Johns Pond and Ashumet Pond are two examples of kettle ponds in the watershed. Waquoit Bay, itself, may have originated as a kettle pond whose southern margin was flooded by sea level rise.

At the close of the Wisconsinan Glacial Stage, the ice sheet retreated and sea level began to rise inundating low lying coastal areas. The action of winds, waves and currents eroded and displaced the loose glacial sand and gravel contributing to the formation of coastal sand dunes, sea cliffs, barrier beaches and salt marshes. These processes continue to alter the dynamic shore.

Waquoit Bay's hydrology is controlled by the region's geology, which is typical of a glacial outwash plain. The unconsolidated sediments of Cape Cod make ideal aquifers. In recognition of the unique groundwater characteristics of Cape Cod, the U.S. Environmental Protection Agency declared this region a Sole-Source Aquifer in 1982, a designation designed to facilitate protection of the water supply. In actuality, the Cape Cod aquifer can be subdivided into six groundwater lenses; the Waquoit Bay watershed lies within the Sagamore or western Cape lens of the Cape Cod Aquifer.

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