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David Z. Piper

Publications and source records attributed to David Z. Piper.

26 records · Page 2Linked to original sources
USGS1987

The stable isotopic composition of a phosphorite deposit: δ13C, δ34S, and δ18O

The stable isotopes of carbon and sulfur in a major marine sedimentary phosphate deposit from the northwestern United States (the Phosphoria Formation of Permian age) characterize the chemical properties of the depositional environment. The δ 34 S and δ 13 C analyses suggest deposition under conditions of variable redox from a solution the acidity of which was controlled by reaction with carbonate rocks and exchange with seawater. The δ 18 O concentration of apetite indicates phosphatization in a shallow sea, during three glacial and intervening interglacial stages. These data tend to corroborate the interpretation of field studies by others, that the apatite formed on a continental shelf in an area of intense oceanic upwelling during several episodes of sea level change.

Deep Sea Research Part A, Oceanographic Research P↗
USGS1982

Distribution, mineralogy, and texture of manganese nodules and their relation to sedimentation at DOMES Site A in the equatorial North Pacific

DOMES Site A, in the equatorial North Pacific, was surveyed in detail in an attempt to relate the distribution of nodules to sedimentation. The sea floor is characterized by a broad east-west-trending valley defined by strongly dissected highlands to the north and south. Sediment recovered from the highlands and from the north margin of the valley is late Quaternary. The associated nodules are small, often polynucleated, have smooth surface textures, and the dominant mineral is δ-MnO 2 . By contrast, cores along the south margin of the valley contain early Tertiary sediment; the nodules usually are large, discoidal in shape, all have a granular surface texture, and the dominant mineral is todorokite. Cores from the central part of the valley share properties with both of the above environments; the sediment is late Quaternary but the nodules are granular with dominant todorokite. The distribution of sediment and abundance of nodules is interpreted to be controlled primarily by the flow of Antarctic Bottom Water through the valley from west to east. The surface texture and mineralogy of the nodules, and possibly their chemical composition, may, in turn, be controlled by properties of the associated sediment.

Deep Sea Research Part A, Oceanographic Research P↗
USGS1977

Composition of Pacific Ocean ferromanganese nodules

Bulk composition of ferromanganese nodules from the pelagic environment of the Pacific Ocean is apparently related to nodule-growth rate, sediment-accumulation rate, and biologic productivity in the overlying seawater. Nodules with a high Mn Fe "> MnFe ratio and high Ni and Cu concentrations tend to occur in areas where primary productivity in the surface layer of the ocean is high and the sediment-accumulation rate low. Nodules with a low Mn Fe "> MnFe ratio and low Ni and Cu concentrations occur in areas either where sediment-accumulation rate is high or biologic productivity is low. They may have a Mn Fe "> MnFe ratio as low as one and accrete at rates as low as 1 mm 10 6 yrs "> 1mm106yrs . Nodules with a larger Mn Fe "> MnFe ratio apparently have growth rates that are greater by as much as a factor of 10.

Marine Geology↗