Source and Dispersion of Surface Sediments in the Gulf of Maine--Georges Bank Area

Abstract

ABSTRACT A study of the mineral composition of the sand fraction (2 to 0.062 mm) of 115 surface samples from the Gulf of Maine--Georges Bank area has defined eight provinces based mainly on heavy mineral composition. Sediments in three provinces, off the Penobscot, Kennebec, and Merrimack Rivers, are of recent origin. The remaining five provinces are composed of relict sediments of which three are of glacial origin. Sediments of Georges Bank are reworked from the Coastal Plain, either derived from rocks underlying the bank or from the Gulf of Maine, in which instance they have been transported to the bank by glaciers. Fine-grained sediments have been winnowed from Georges Bank and transported into the Gulf of Maine where they have mixed with the glacial sediments of that area. Mineral composition throughout the area of study is controlled mainly by the source, though reworking has resulted in some modification. This modification is most pronounced in the high energy areas of Georges Bank and off Cape Cod, where more resistant heavy minerals predominate. The sediments in these areas are also better sorted and have lower feldspar-quartz ratios than the sediments in the low energy areas of the Gulf of Maine. Reworking of sediments on the ridge areas in the Gulf of Maine was anticipated, but not definitively observed. This may be due to the small number of examined samples or lack of sufficient time for these sediments to come to equilibrium with their environment.