The data for this study are derived from 8 traverses across the continental shelf, from Cape Cod to Cape Canaveral, and 3 from the Gulf of Maine. Samples were spaced from 0.5 to 2 miles apart.

The source of the present-day sediment is largely reworked glacial debris for the northern lines, and for those outside the limits of the ice advance, reworked Coastal Plain deposits. Although the distribution of the sediments appears very diverse when the shelf is considered in small areas, certain uniformities in their arrangement appear when it is taken by regions. This distribution indicates that the bottom deposits are becoming adjusted to present sea-level, and that the differences are largely dependent on source of supply.

Calcium carbonate is present in insignificant amounts north of Cape Hatteras. South of this cape however, it is a main constituent of the bottom deposits, often reaching 50-80 per cent. It is derived from the skeletons of various organisms which have been comminuted to the same sizes as the inorganic particles, and also from oolites. Some of the lime is undoubtedly derived from the reworking of older deposits.

The Gulf Stream is the only one of the currents making up part of the main circulatory system of the ocean that has any effect on the sediments of the continental shelf. South of Cape Hatteras the continental slope is, for the most part, swept bare of unconsolidated material by this current. A combination of wave action and tidal currents is sorting the bottom deposits in water shallower than 60 to 70 meters and occasionally to greater depths where the tidal currents are exceptionally strong. Wave action is known to extend to the bottom all over the shelf in winter but is not effective in agitating the sediments below the depths given above.

A profile of equilibrium has been developed on the inner halves of the northern lines and is best exemplified on the Marthas Vineyard traverse. The traverses south of Cape Hatteras represent profiles that are still far above wave base.

South of New England is a large area in which quartz sand grains, exhibiting a very high degree of rounding, are found in abundance. Most of these grains have a mat surface unless it has been secondarily removed. They are thought to be the remains of ancient dunes formed during the lower stands of the sea during the Pleistocene. Many sediments on the break in slope are coarser than those immediately inshore. They are also considered to be residual from a lowered sea-level.

The grade size does not decrease uniformly in an offshore direction. However the bottom deposits, by their very diversity, are merely a modern illustration of conditions that have been in operation throughout the whole history of Coastal Plain deposition. Sedimentation along the margins of a major ocean must not be considered typical of an inland sea.