How do we know that parts of southern Maine were covered by the ocean when the last glacial ice sheet melted away?
Many low-lying areas of southern Maine are blanketed by clay deposits. These clays are know to be marine, because they contain fossil shells of clams, mussels, scallops, barnacles, and other marine life found in the ocean today. In some places where the clay is not weathered, the actual shells are fully preserved. Elsewhere they have dissolved away, leaving only their impressions.
