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Occurrence and preservation of Eocene squamariacean and coralline rhodoliths: Eau, Tonga Occurrence and preservation of Eocene squamariacean and coralline rhodoliths: Eau, Tonga

A widespread rhodolith facies occurs within middle Eocene limestones of Eua, Tonga (Fig. 1). These limestones, first described by Hoffmeister (1932), represent a portion of a broad, early Tertiary platform that developed in the Tonga area prior to disruption and uplift by later Tertiary plate movements (Kroenke and Tongilava 1975). Algal rhodoliths form beds several meters thick within...
Authors
Binyamin Buchbinder, Robert B. Halley

Bottom current and sediment transport on San Pedro Shelf, California Bottom current and sediment transport on San Pedro Shelf, California

GEOPROBE (Geological Processes Bottom Environmental) tripods were used to measure bottom currents, pressure, and light transmission and scattering and to obtain time-series photographs of the sea floor at depths of 23 m and 67 m on San Pedro shelf between 18 April and 6 June 1978. Winds were light ( 5 m/s) with a mean direction from the southwest throughout the measurement period. Hourly...
Authors
David E. Drake, David A. Cacchione, Herman A. Karl

Ferromanganese crusts from Necker Ridge, Horizon Guyot and S.P. Lee Guyot: Geological considerations Ferromanganese crusts from Necker Ridge, Horizon Guyot and S.P. Lee Guyot: Geological considerations

Necker Ridge, Horizon Guyot and S.P. Lee Guyot in the Central Pacific were sampled, seismically surveyed, and photographed by bottom cameras in order to better understand the distribution, origin, and evolution of ferromanganese crusts. Necker Ridge is over 600 km long with a rugged crest, pods of sediment to 146 m thick, slopes that average 12° to 20°, and debris aprons that cover some...
Authors
James R. Hein, Frank T. Manheim, William C. Schwab, Alice S. Davis

Why deposits of longitudinal dunes are rarely recognized in the geologic record Why deposits of longitudinal dunes are rarely recognized in the geologic record

Dunes that are morphologically of linear type, many of which are probably of longitudinal type in a morphodynamic sense, are common in modern deserts, but their deposits are rarely identified in aeolian sandstones. One reason for non-recognition of such dunes is that they can migrate laterally when they are not exactly parallel to the long-term sand-transport direction, thereby...
Authors
David M. Rubin, Ralph E. Hunter

Foraminiferal, lithic, and isotopic changes across four major unconformities at Deep Sea Drilling Project Site 548, Goban Spur Foraminiferal, lithic, and isotopic changes across four major unconformities at Deep Sea Drilling Project Site 548, Goban Spur

Sediment samples taken at close intervals across four major unconformities (middle Miocene/upper Miocene, lower Oligocene/upper Oligocene, lower Eocene/upper Eocene, lower Paleocene/upper Paleocene) at DSDP-IPOD Site 548, Goban Spur, reveal that coeval biostratigraphic gaps, sediment discontinuities, and seismic unconformities coincide with postulated low stands of sea level...
Authors
C. Wylie Poag, Leslie A. Reynolds, James M. Mazzullo, Loyd D. Keigwin

Dolomitization in a mixing zone of near-seawater composition, Late Pleistocene, northeastern Yucatan Peninsula Dolomitization in a mixing zone of near-seawater composition, Late Pleistocene, northeastern Yucatan Peninsula

Patches of dolomite occur in cores of reefal limestone from the shallow subsurface on the northeastern coast of the Yucatan Peninsula. This limestone accumulated during an interglacial high stand of sea level about 200,000 years ago. Dolomitization was preceded by freshwater diagenesis, including precipitation of sparry calcite cement, stabilization of Mg-calcitic skeletal fragments, and...
Authors
W. C. Ward, Robert B. Halley

High-frequency observations and source parameters of microearthquakes recorded at hard-rock sites High-frequency observations and source parameters of microearthquakes recorded at hard-rock sites

We have estimated the source parameters of 53 microearthquakes recorded in July 1983 which were aftershocks of the Miramichi, New Brunswick, earthquake that occurred on 9 January 1982. These events were recorded by local three-component digital seismographs at 400 sps/component from 2-Hz velocity transducers sited directly on glacially scoured crystalline basement outcrop. Hypocentral...
Authors
Edward Cranswick, Robert Wetmiller, John Boatwright

Monitoring the hydrothermal system in Long Valley caldera, California Monitoring the hydrothermal system in Long Valley caldera, California

An ongoing program to monitor the hydrothermal system in Long Valley for changes caused by volcanic or tectonic processes has produced considerable data on the water chemistry and discharge of springs and fluid temperatures and pressures in wells. Chemical and isotopic data collected under this program have greatly expanded the knowledge of chemical variability both in space and time...
Authors
C. D. Farrar, M.L. Sorey
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