Publications
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Paleogene paleoceanography of the Arctic Ocean is constrained by the middle or late Eocene age of USGS Core Fl-422: Evidence from silicoflagellates
Arctic Ocean Core Fl-422 has been of central importance in Arctic tectonics and paleoceanography because it provides the sole evidence for early Cenozoic marine conditions in the Arctic. The presence of several Eocene and Eocene or Oligocene guide species of silicoflagellates in samples from this core shows that it is no older than middle Eocene, and is not Paleocene as previously reported. There
Authors
David Bukry
Ultrathin lava layers exposed near San Luis Obispo Bay, California
Sequences of extraordinarily thin (1–5 cm thick) lava layers, resembling individual lava flows, are interbedded with Jurassic and Cretaceous pillowed lava flows near San Luis Obispo Bay on the California coast. Such layers are formed inside submarine pillowed lava pipes or flow lobes. As the lava surface in a pillow pipe falls to a lower level owing to diminished supply entering the pipe, water en
Authors
James G. Moore, D.W. Charlton
Lead and strontium isotopic evidence for crustal interaction and compositional zonation in the source regions of Pleistocene basaltic and rhyolitic magmas of the Coso volcanic field, California
The isotopic compositions of Pb and Sr in Pleistocene basalt, high-silica rhyolite, and andesitic inclusions in rhyolite of the Coso volcanic field indicate that these rocks were derived from different levels of compositionally zoned magmatic systems. The 2 earliest rhyolites probably were tapped from short-lived silicic reservoirs, in contrast to the other 36 rhyolite domes and lava flows which t
Authors
C. R. Bacon, H. Kurasawa, M.H. Delevaux, R. W. Kistler, B. R. Doe
Magmatic inclusions in rhyolites, contaminated basalts, and compositional zonation beneath the Coso volcanic field, California
Basaltic lava flows and high-silica rhyolite domes form the Pleistocene part of the Coso volcanic field in southeastern California. The distribution of vents maps the areal zonation inferred for the upper parts of the Coso magmatic system. Subalkalic basalts (<50% SiO2) were erupted well away from the rhyolite field at any given time. Compositional variation among these basalts can be ascribed to
Authors
C. R. Bacon, J. Metz
Upper Cenozoic silicoflagellates from offshore Ecuador, Deep Sea Drilling Project Site 504
Diverse and abundant late Miocene to Pleistocene silicoflagellates at DSDP Site 504 can be correlated by tropical biostratigraphic zones and relative paleotemperature values to eastern tropical Pacific reference site DSDP 503A farther to the west. Early Pliocene assemblages, which were poorly known until now, are present and can be correlated locally between DSDP Holes 504, 503A, and 495, using sp
Authors
David Bukry
Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.
New investigations of the geology of Crater Lake National Park necessitate a reinterpretation of the eruptive history of Mount Mazama and of the formation of Crater Lake caldera. Mount Mazama consisted of a glaciated complex of overlapping shields and stratovolcanoes, each of which was probably active for a comparatively short interval. All the Mazama magmas apparently evolved within thermally and
Authors
C. R. Bacon
Nature and mechanics of the mount St Helens rockslide — avalanche of 18 May 1980
The bulging sector of the north slope of Mount St. Helens collapsed on 18 May 1980, triggered by an earthquake, thereby creating a tremendous mass movement. This movement in turn initiated volcanic eruptions resulting in the formation of an avalanche of debris. Limit equilibrium analysis of the slope suggests that failure was due to several culminating factors, including progressive strength losse
Authors
Barry Voight, R. J. Janda, H. Glicken
Eruption-triggered avalanche, flood, and lahar at Mount St. Helens - Effects of winter snowpack
An explosive eruption of Mount St. Helens on 19 March 1982 had substantial impact beyond the vent because hot eruption products interacted with a thick snowpack. A blast of hot pumice, dome rocks, and gas dislodged crater-wall snow that avalanched through the crater and down the north flank. Snow in the crater swiftly melted to form a transient lake, from which a destructive flood and lahar swept
Authors
R. B. Waitt, T. C. Pierson, N. S. MacLeod, R. J. Janda, B. Voight, R. T. Holcomb
Patterns of sediment concentration in hyperconcentrated flows at Mount St. Helens
No abstract available.
Authors
Randy L. Dinehart
Semiquantitative spectrographic analyses of stream-sediment samples from the Wenaha Tucannon Wilderness, Washington and Oregon
No abstract available.
Authors
Donald A. Swanson, Thomas L. Wright
Time-predictable bimodal volcanism in the Coso Range, California
The bimodal Pleistocene part of the Coso volcanic field has erupted rhyolite and basalt at constant long-term rates during the past ∼0.5 m.y. Both basalt and high-silica rhyolite were erupted in several independent, geologically brief episodes. The interval between eruptions of rhyolite was proportional to the volume of the preceding eruption. Basaltic eruptions appear to have followed a similar p
Authors
Charles R. Bacon
Cenozoic silicoflagellates from offshore Guatemala, Deep Sea Drilling Project Site 495
Diverse lower Miocene to Pleistocene silicoflagellate assemblages occur at Deep Sea Drilling Project Site 495, but many samples are dominated by one or two taxa. Low-latitude zonation can be applied throughout. Cool-indicating Distephanus speculum s. ampl. is only abundant in the upper Miocene; however, relative paleotemperature values (Ts) suggest temperature extremes in the lower Miocene similar
Authors
David Bukry