Seismic reflection study of the geologic structure underlying southern Narragansett Bay, Rhode Island

A subbottom reflection survey of southern Narragansett Bay, Rhode Island was made by means of a continuous seismic reflection technique (the Continuous Seismic Profiler)developed at the Woods Hole Oceanographic Institution (Knott and Hersey, 1956). The observational program was conducted in May, 1958 under contract with the Corps of Engineers, U. S. Army, and in May, 1960 under contract with the Bureau of Ships, U . S. Navy, to obtain foundation data for locating hurricane barriers (Corps of Engineers, 1957) and to develop techniques for studying the geologic structure of shallow water areas. At the Woods Hole Oceanographic Institution this work is part of a continuing, broader program directed toward describing the structures and tracing the geologic history of continental margins. The Continuous Seismic Profiler employs a wide-band sound source the pulses from which are reflected from the bottom and from sediment and rock layers beneath the bottom. The sound pulse is synchronized with the sweep of a Precision Graphic Recorder (PGR), which records sound energy received at an underwater detector. (In 1958 the sound source was an early form of the Sparker, while in 1960 the Edgerton Thumper was the source. (These instruments are described below.) When the sound source and the detector are towed from a boat, the reflected sound energy is recorded to present a continuously correlated picture of subbottom structure. Measurements in Narragansett Bay were made south of the Jamestown Bridge in the West Passage and between Conanicut Island and Newport Neck in the East Passage (Fig . 1A and lB). Two additional traverses were made across the bay in areas to the north where core data are available (Fig. 2).The Bureau of Ships under Contract NObsr 72521 and the U. S. Army Corps of Engineers under Contract DA-19-016 CIVENG-58-6

Table 1. Composition of manganese crusts from the Atlantis Fracture Zone

Summaries of the transition element chemistry of oceanic ferro-manganese deposits report compositional trends related to water depth and to geographic proximity to continental margins1-4. Explanations of compositional variations include continental source influence3, 5, 6, diagenetic environmental control of manganese mineralogy that regulates the trace metal composition1, 3, 7, ionic mobility in interstitial solutions during diagenesis3, 8-10, and volcanic or hydrothermal influence3, 11-14. Glasby15 rejects a significant pressure control on manganese oxide mineralogy on thermodynamic grounds

(Table 2, Annex), Manganese crusts and manganese coated rocks recovered from study area (lat 26°N)

An asymmetric tectonic fabric was delineated by narrow-beam bathymetric profiles in a 180-km2 area of the Mid-Atlantic Ridge crest at lat 26°N. Features of the tectonic fabric are a continuous rift valley offset by small (<10-km) transform faults and minor fracture zones expressed as valleys with intervening ridges that trend normal and oblique to the two sides of the rift valley. The discharge zone of a postulated sub-sea-floor hydrothermal convection system is focused by faults on the southeast wall of the rift valley and driven by intrusive heat sources beneath the rift valley. The rift valley has a double structure consisting of linear segments, bounded by ridges, and basins at the intersections of the minor fracture zones. The double structure of the rift valley acts like a template that programs the reproduction of the tectonic fabric. The minor fracture zones form an asymmetric V about the rift valley at variance with the symmetric small circles formed by major fracture zones. To reconcile the asymmetry of minor fracture zones with the symmetry of major fracture zones, it is proposed that the minor fracture zones have been preferentially reoriented by an external stress field attributed to interplate and intraplate motions. Major fracture zones remain symmetric under the same stress field owing to differential stability between minor and major structures of oceanic lithosphere

Geochemistry on manganese deposit from the Median Valley of the Mid-Atlantic Ridge

A manganese oxide crust from an extensive deposit in the median valley of the Mid-Atlantic Ridge was found to be unusually high in manganese (up to 39.4% Mn), low in Fe (as low as 0.01% Fe), low in trace metals and deficient in Th230 and Pa231 with respect to the parent uranium isotopes in the sample. The accumulation rate is 100 mm to 200 mm/10 million year, or 2 orders of magnitude faster than the typical rate for deep-sea ferromanganese deposits. The rapid growth rate and unusual chemistry are consistent with a hydrothermal origin or with a diagenetic origin by manganese remobilized from reduced sediments. Because of the association with an active ridge, geophysical evidence indicative of hydrothermal activity, and a scarcity of sediment in the sampling area, we suggest that a submarine hot spring has created the deposit

Improgan, a cimetidine analog, induces morphine-like antinociception in opioid receptor-knockout mice.

Improgan is an analog of the

Opioids activate brain analgesic circuits through cytochrome P450/epoxygenase signaling.

To assess the importance of brain cytochrome P450 (P450) activity in opioid analgesic action, we generated a mutant mouse with brain neuron-specific reductions in P450 activity; these mice showed highly attenuated morphine antinociception compared with controls. Pharmacological inhibition of brain P450 arachidonate epoxygenases also blocked morphine antinociception in mice and rats. Our findings indicate that a neuronal P450 epoxygenase mediates the pain-relieving properties of morphine. © 2010 Nature America, Inc. All rights reserved