Publications

Palaeomagnetic results have been obtained from thirty sites in intrusive and extrusive rocks of Oligocene age from the San Juan Mountains, south-western Colorado. All specimens from each site were subjected to af demagnetization, and the reliability of each site determined. Twenty-three sites gave reliable results. Because five sites from the thick intracaldera part of the La Jara Canyon Member of

Silicoflagellates are important biostratigraphic markers for age determination in nontropical regions because age-diagnostic calcareous microfossils are sparse. Upper Cretaceous and Cenozoic biostratigraphic zonation is proposed, based on silicoflagellates from Deep Sea Drilling Project sites in the subantarctic region.

The inner rift valley of the Mid-Atlantic Ridge at 36°48′ N. is 1.5 to 3 km wide and 100 to 400 m deep. It is symmetrical in profile with a discontinuous medial ridge 100 to 240 m high and 800 to 1,300 m wide along its axis. The medial ridge is replaced every 1 to 3 km with a central trough 200 to 600 m wide.The medial ridge is apparently built by eruptions of pillow basalt recurring at intervals

No abstract available.

Study of major element chemical analyses of Columbia River basalt leads to a grouping of most of the analyses into 11 chemical types which are distinguished with little overlap on a SiO2-MgO variation diagram. Other diagnostic variation diagrams are total iron (‘FeO’)-MgO, K2O-MgO, and TiO2-MgO.A four-unit informal stratigraphy has been adopted in order to define the relations between chemical com

The 1959 eruption of Kilauea volcano is unique among recent Kilauea summit eruptions (1952 to 1968) in at least two respects: (1) a large collapse of Kilauea summit accompanied the eruption, and (2) the erupted lavas show a complex variation in their bulk chemical composition. Both features suggest that the 1959 eruption was fed from a source different from that which fed other summit eruptions in

Review of quantitative data, restricted range in gold content (rarely more than 10 ppb, generally below 5 ppb), mafic rocks have more, so do early crystallizing minerals, no use in exploration, factors other than concentration determine mineralization; examples

Rocks of the Late Cretaceous composite Boulder batholith, though successively emplaced in a relatively small segment of the Earth's crust within a very brief time span (78 to 68 m.y.), can be grouped chemically into two magma series: (1) the main series, defined principally by plutons in the central and northern parts of the batholith; and (2) the sodic series, defined mostly by plutons in the sou

Recent literature contains numerous references to basement ages and basement depths determined by the Deep Sea Drilling Project. The data are derived from a variety of sources, many of them inadequately documented or preliminary, and are not uncommonly inaccurate or conflicting. In this paper we present tabulations of basement ages and depths from DSDP Legs 5, 8, 9, and 16 in the eastern equatoria

Late Pleistocene or Recent lavas from San Quintin, Baja California are basanitoids and alkali basalts. The surface quench temperatures of the lavas average 1 005° C with log fO2fO2=−11.4, as deduced from the groundmass Fe-Ti oxides. Spinel lherzolite xenoliths and megacrysts of augite and andesine have been found in lava flows and cinder deposits. Using analytical data on the rocks and minerals an

Lava from the Mauna Ulu eruption on Kilauea Volcano entered the sea on the south coast of the Island of Hawaii three times from 1969 to 1971. Two of these flows were investigated underwater by divers, one while lava was actively flowing.The June 1969 flow entered the sea as a narrow flow of aa. Below sea level, the flow maintained continuity and flowed at least several hundred meters to a depth be

A new descriptive term, comb layering, is proposed to replace the informal term Willow Lake-type layering, first introduced by Poldervaart and Taubeneck (1959) to describe layering in granitoid rocks in which constituent crystals are oriented approximately perpendicular to individual layers. The term schlieren layering is proposed to describe the “normal” layering of granitic rocks defined by alte