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.

Automation of antimicrobial susceptibility testing.

Laboratory services lag significantly behind the time demands of the clinician in determining the appropriate antimicrobic drug to treat a bacterial infection. The authors discuss several new automated optical systems that promise to shorten the time lag for results, as well as lead to improved precision and standardization. The advantages of expressing antimicrobic susceptibility results as Minimum Inhibitory Concentration (MIC) over the three classifications of sensitive, intermediate, or resistant commonly determined by the Kirby-Bauer disc diffusion method are discussed. Computerization is a central feature of emerging instrumentation for antimicrobic susceptibility testin, and it will be potentially useful in providing interpretive data relating the MIC to specific dose-site combinations. The paper is concluded by short descriptions of nonoptical techniques that investigators have used to measure bacterial growth.

Methane-derived marine carbonates of pleistocene age.

In some calcium carbonate-bearing sandstones from the edge of the continental shelf off the northeast United States, the deltaC(13) range is from -30 and -60 per mil for both aragonite and high-magnesium calcite. The deltaC(13) of co-existing shells of Modiolus sp. is normal (+ 1.7 to -2.7 per mil). The deltaO(18) values of around + 3.5 per mil in all samples suggest deposition at temperatures around 0 degrees C. Quaternary methane oxidized either chemically or microbiologically to carbon dioxide is the probable source of carbon in these carbonates.