The effect of the new Massachusetts Bay sewage outfall on the concentrations of metals and bacterial spores in nearby bottom and suspended sediments.

Since the new outfall for Boston's treated sewage effluent began operation on September 6, 2000, no change has been observed in concentrations of silver or Clostridium perfringens spores (an ecologically benign tracer of sewage), in bottom sediments at a site 2.5 km west of the outfall. In suspended sediment samples collected with a time-series sediment trap located 1.3 km south of the outfall, silver and C. perfringens spores increased by 38% and 103%, respectively, in post-outfall samples while chromium, copper, and zinc showed no change. All metal concentrations in sediments are <50% of warning levels established by the Massachusetts Water Resources Authority. An 11-year data set of bottom sediment characteristics collected three times per year prior to outfall startup provides perspective for the interpretation of post-outfall data. A greater than twofold increase in concentrations of sewage tracers (silver and C. perfringens) was observed in muddy sediments following the exceptional storm of December 11-16, 1992 that presumably moved contaminated inshore sediment offshore.

Upper wisconsinan till recovered on the continental shelf southeast of new England.

Basal till was identified in two sediment cores collected about 69 kilometers southeast of Nantucket Island on the east and west sides of Great South Channel. These are the first samples of till collected on the outer continental shelf off the northeastern United States. The carbon-14 age of the total organic carbon in the tills provides a "no older than" age of about 20,000 years before present and suggests that the tills were deposited during the late Wisconsinan glaciation. This conclusion is in support of the hypothesis of an extensive Laurentide ice sheet that extended to the northern side of Georges Bank.

U.s. Geological survey core drilling on the atlantic shelf.

The first broad program of scientific shallow drilling on the U.S. Atlantic continental shelf has delineated rocks of Pleistocene to Late Cretaceous age, including phosphoritic Miocene strata, widespread Eocene carbonate deposits that serve as reflective seismic markers, and several regional unconformities. Two sites, off Maryland and New Jersey, showed light hydrocarbon gases having affinity to mature petroleum. Pore fluid studies showed that relatively fresh to brackish water occurs beneath much of the Atlantic continental shelf, whereas increases in salinity off Georgla and beneath the Florida-Hatteras slope suggest buried evaporitic strata. The sediment cores showed engineering properties that range from good foundation strength to a potential for severe loss of strength through interaction between sediments and man-made structures.