Publications

No abstract available.

No abstract available.

The research results described in the following summaries were submitted by the investigators on October 20, 1983 and cover the 6-month period from April 1, 1983 through September 30, 1983. These reports include both work performed under contracts administered by the Geological Survey and work by members of the Geological Survey. The report summaries are grouped into the four major elements o

No abstract available.

Nineteen pillow basalts dredged within the rift valley of the Mid-Atlantic Ridge at36.8°N were studied by the Thellier stepwise heating method in order to determine the paleointensity of the geomagnetic field when they erupted on to the sea floor. Previously reported fission track ages are 2,000 to 6,000 years for the youngest rocks (mainly olivine basalts) and 10,000 to 100,000 years for the othe

Previous geological and geophysical investigations have suggested that the Mississippi Embayment is the site of a Late Precambrian continental rift that was reactivated in the Mesozoic. New information on the deep structure of the northern Mississippi Embayment, gained through an extensive seismic refraction survey, supports a rifting hypothesis. The data indicate that the crust of the Mississippi

No abstract available.

A two day selection of MAGSAT data is fit by spherical harmonic series truncated at increasing levels NF in the range 2<NF<14 to determine the extent to which the geomagnetic Gauss coefficients depend upon truncation level of the fit. The dependence is found to be concentrated in the range n<NF≲n+4 decreasing rapidly in magnitude to a few nanotesla as n increases to about 6.Several geomagnetic pro

Gravity models computed for a profile across the long-wavelength paired negative-positive Bouguer anomalies of the southern Appalachian Mountains show that the large negative anomaly can be explained by a crustal root zone, whereas the steep gradient and positive anomaly east of the root may be explained equally well by three different geometries: a suture zone, a mantle upwarp, or a shallow body.

A close spatial and temporal association between three aseismic uplift episodes and subsequent large (M ≈ 7) earthquakes on the Izu Peninsula, Japan, suggests a causal relation. Quaternary geology, as well as studies by other workers, indicates a volcanic origin for the observed uplift, and we use a simple inflation model constrained by leveling data to compute the expected increments in normal an

Many landforms in Martian outflow channels have characteristics that suggest sculpture by glaciers, ice streams, or ice sheets. Viking Orbiter and terrestrial satellite images were examined at similar resolution to compare features of the Martian outflow channels to features produced by the movement of ice on earth. Many resemblances were found. They include the anastomoses, sinuosities, and U‐sha

The reflection and refraction of general (homogeneous or inhomogeneous) plane P and type-I S(SV) body waves incident on plane boundaries are considered for general linear viscoelastic solids. Reflection—refraction laws, physical characteristics of the waves, and the nature of critical angles are examined in detail at welded boundaries and a free surface. General visco-elasticity with no low-loss a