Chemistry of volcanic ash layers from the southern Atlantic

Petrographic and geochemical investigations were carried out on 21 ash layers from four sites of ODP Legs 113 and 114 in the southern Atlantic Ocean. With the help of geochemical data and petrographic characterization three rock series can be distinguished for stratigraphically different ash layers from Site 701 (Leg 114) located east of the South Sandwich Island Arc, whereas the Leg 113 tephras from the southern slope of the South Orkney Microcontinent belong to another magmatic series. Geochemical correlation of the Leg 113 tephras with possible source areas indicates that they were probably erupted from the Antarctic Peninsula. The Miocene ashes from Site 701 are probably derived from the now-extinct Discovery Arc, the precursor of the South Sandwich Islands. The Pliocene ashes from the site show some affinity with the South Shetland Islands, although the available data do not permit a clear correlation. The Quaternary ashes from Site 701 display a chemistry typical of island-arc tholeiites and are therefore most probably derived from eruptions on the South Sandwich Islands. Because of their distant position the southern Andes seem to be rather improbable as a potential source region for the tephra layers investigated.

Chemical composition of volcanic ash layers from ODP Leg 134 sites

Volcanic ash layers (1-3 cm thick) are abundant in the North Aoba Basin drill sites but less common at forearc sites. Ash deposited on the forearc slopes is liable to be redistributed as turbidites. In addition, the westerly upper winds also minimize ash-fall on the western (forearc) side of the New Hebrides Island Arc. Crystalline components in the ashes are primarily plagioclase (An90-An44), clinopyroxene (Ca46Mg49Fe5-Ca43Mg33Fe24), olivine (Fo87-Fo62), and titanomagnetite. There are also small amounts of orthopyroxene, magnetite, apatite, and quartz. Glass shards occur in most of the ashes and range in composition from basalt to rhyolite. There is often a variety of glass compositions within a single ash layer. One explanation for this is that the rate of accumulation of ash from several different eruptions or eruptive phases exceeded the background sedimentation rate: there may also have been a certain amount of reworking. The high-K and low-K trends previously recognized in volcanic rocks from the New Hebrides Island Arc are clearly represented in the Leg 134 glasses. All of the ashes investigated here are thought to have originated from the Central Chain volcanoes. The source of the high-K group was probably the Central Basin volcanoes of Santa Maria, Aoba, and Ambrym. The lower-K series includes a distinctive group of dacites and is likely to have originated from the Epi-Tongoa-Tongariki sector of the arc where major pyroclastic eruptions, associated with caldera collapse, have occurred during the Holocene, perhaps as recently as 400 yr ago.

Labor legislation of Ecuador /

"This translation of the labor laws of Ecuador was made under the direction of Ethel Y. Larson, of the Bureau of Labor Statistics."

Labor legislation of Paraguay /

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Labor legislation of Venezuela /

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A study of the feasibility of utilizing solid wastes for building materials : phase III and IV summary reports /

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Mutual fund legislation of 1967 : hearings ... Ninetieth Congress, first session, on S. 1659.

Pt. 3 on Amendment No. 438 to S. 1659.

Investigation of feasibility of utilizing available heat resistant materials for hypersonic leading edge applications.

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State solar energy legislation of 1976 : a review of statutes relating to buildings /

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State solar energy legislation of 1977 : a review of statutes relating to buildings /

Feb. 1979.

FIFRA extension [microform] : hearing before the Subcommittee on Agricultural Research and General Legislation of the Committee on Agriculture, Nutrition, and Forestry, United States Senate, Ninety-sixth Congress, first session, on S. 717 ... April 26, 1979.

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Require the Secretary of Agriculture to disseminate farm income estimates [microform] : hearing before the Subcommittee on Agricultural Research and General Legislation of the Committee on Agriculture, Nutrition, and Forestry, United States Senate, Ninety-seventh Congress, second session, on S. 2291 ... September 14, 1982.

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Laws of Barbados. 1894-2 to [1912-7] With table shewing effect of the legislation of 1894-2 to [1910-34] inclusive. And an index by Sir W.H. Greaves ... vol. IV-[VII]

Vol. 7, pt. 3, 1911-1--1912-7, does not have the "table shewing effect of the legislation."

Legislation of interest to women, ... General Assembly, final report.

Description based on: 1983; title from cover.