Publications

The Mariano Lake uranium deposit, hosted by the Brushy Basin Member of the Jurassic Morrison Formation, occurs in the trough of an east-west trending syncline at the western end of the Smith Lake-Mariano Lake group of uranium deposits near Crownpoint, New Mexico. The orebody, which contains abundant amorphous organic material, is situated on the reduced side of a regional reduction-oxidation (redo

No abstract available. 

Limestones of mid-Cretaceous age containing as much as 8.6 percent organic carbon were cored at one site (463) in the Mid-Pacific Mountains and at two sites (465, 466) on southern Hess Rise, central North Pacific Ocean, during Leg 62 of the Deep Sea Drilling Project. In the Mid-Pacific Mountains, three layers containing more than 2% organic carbon are associated with volcanic ash in silicified lim

The Mid-Pacific Mountains constitute one of the largest aseismic rises in the central North Pacific Ocean. They have been generated by mid-plate volcanic events prior to Barremian time, but their volcanic activity continued through the remainder of the Cretaceous. Evidence of the latest stages of this volcanism are the trachytic ashes included in mid- and Late Cretaceous sediments and the presence

The geology of Hess Rise is interpreted from studies of morphology and structure, igneous petrology, sediment lithofacies, seismic stratigraphy, and paleoenvironments. Hess Rise probably formed at a triple junction, between 116 and 95 m.y. ago, in the equatorial zone of the southern hemisphere. A large archipelago, formed by volcanism, subsequently moved northward as part of the Pacific Plate and

No abstract available.

The mechanical properties of elemental sulfur are such that the upper crust of Io cannot be primarily sulfur. For heat flows in the range 100–1000 ergs cm−2, sec−1, sulfur becomes ductile within several hundred meters of the surface and would prevent the formation of calderas with depths greater than this. However, the one caldera for which precise depth data are available is 2 km deep, and this v

Two classes of fracture zones are distinguished on the basis of their orientations with respect to a spreading axis and length of associated ridge-ridge transform offset. (1) Minor fracture zones associated with transform faults of short offset (<30 km; minitransforms); the minor fracture zones may exhibit an asymmetric V-shaped configuration with respect to a spreading axis at variance with small

No abstract available.

Air fall ash beds (Pearlette) originating from rhyolitic eruptions in the Yellowstone‐Island Park region of Wyoming and Idaho are discontinuous but widespread throughout the western United States. Accumulation and deposition of ashes occurred in low‐energy fluvial and lacustrine environments. These ash beds have been correlated, according to their chemistry and remanent magnetism, with specific er

Tree-ring analysis can be a reliable method of determining past snow avalanche events when good historical records are lacking. Characteristic features in the tree-ring record indicative of disturbance include: (1) the occurrence of reaction wood, (2) abrupt changes in growth rate, (3) age of scars caused by avalanche impact, (4) age of trees in reforested tracks, and (5) examination of a “new lea

Unsorted and unstratified deposits of volcanic rock debris typically flank recently active stratovolcanoes. It is often difficult, using standard geologic procedures, to establish whether a particular deposit was emplaced by a pyroclastic flow, lahar, rock avalanche, or glacier. Determination of the emplacement temperatures of clasts contained in the deposit aids in discriminating among some of th