Magmatic evolution of the Gulf of California rift
Michael G. Sawlan
J. Paul Dauphin, Bernd R. T. Simoneit, editor(s)
1991, Book chapter, The gulf and peninsular province of the Californias
Magmatic events in the Baja peninsula-Gulf of California region are closely related to sequential tectonic regimes of: (1) late Tertiary subduction beneath the continental margin until ~16 to 12.5 Ma; and (2) continental to oceanic rifting that began about 13 Ma. Orogenic calcalkaline volcanic rocks formed subparallel belts of rhyolite...
The Briggs Creek Amphibolite, Klamath Mountains, Oregon: Its origin and dispersal
Robert G. Coleman, Marvin A. Lanphere
1991, New Zealand Journal of Geology and Geophysics (34) 271-284
The Briggs Creek Amphibolite (BCA) in southwestern Oregon is an allochthonous slice of metamorphosed oceanic crust emplaced during the Nevadan orogenic event. Even though the evidence is not clear, the authors prefer to have the protolith for the BCA formed in a back‐arc basin contemporaneously as part of the Josephine...
Intrusion of horizontal dikes: tectonic significance of Middle Proterozoic diabase sheets widespread in the upper crust of the southwestern United States
K. A. Howard
1991, Journal of Geophysical Research (96) 12461-12478
Initially horizontal sheet intrusions of Middle Proterozoic diabase are abundant in a region 650 by 300 km across in Arizona and California. The diabase forms discordant sheets in basement granite and gneiss and sills in overlying shelf sedimentary sequences. Massive granite is the most common...
Modelling the petrogenesis of high Rb/Sr silicic magmas
A. N. Halliday, J.P. Davidson, W. Hildreth, P. Holden
1991, Chemical Geology (92) 107-114
Rhyolites can be highly evolved with Sr contents as low as 0.1 ppm and Rb Sr > 2,000. In contrast, granite batholiths are commonly comprised of rocks with Rb Sr 100. Mass-balance modelling of source compositions, differentiation and contamination using the trace-element geochemistry of...
Origin of xenoliths in the trachyte at Puu Waawaa, Hualalai Volcano, Hawaii
David A. Clague, Wendy A. Bohrson
1991, Contributions to Mineralogy and Petrology (108) 439-452
Rare dunite and 2-pyroxene gabbro xenoliths occur in banded trachyte at Puu Waawaa on Hualalai Volcano, Hawaii. Mineral compositions suggest that these xenoliths formed as cumulates of tholeiitic basalt at shallow depth in a subcaldera magma reservoir. Subsequently, the minerals in the xenoliths underwent subsolidus reequilibration that particularly affected chromite...
Oligocene basaltic volcanism of the northern Rio Grande Rift: San Luis Hills, Colorado
R. A. Thompson, C.M. Johnson, H. H. Mehnert
1991, Journal of Geophysical Research (96) 13577-13592
The inception of the Rio Grande rift in northern New Mexico and southern Colorado was accompanied by voluminous mafic volcanism preserved in part as erosional remnants on an intrarift horst within the current axial rift graben of the San Luis Valley. Oligocene (∼26 Ma) volcanic...
The late Cenozoic diatom stratigraphy and paleolimnology of Tule Lake, Siskiyou Co. California
J.P. Bradbury
1991, Journal of Paleolimnology (6) 205-255
Lacustrine diatoms are diverse, well preserved and abundant in cores of lake sediment to 334 m depth near the town of Tulelake, Siskiyou County, northern California. The cores have been dated by radiometric, tephrochronologic and paleomagnetic techniques, which indicate a basal age of about 3 million years (Ma) and a...
Infectious hematopoietic necrosis (IHN) and viral hemorrhagic septicemia (VHS): Detection of the trout antibodies to the causative viruses by means of plaque neutralization, immunofluorescence, and enzyme-linked immunosorbent assay
P. E. Vestergard Jorgensen, N.J. Olesen, N. Lorenzen, J. R. Winton, S.S. Ristow
1991, Journal of Aquatic Animal Health (3) 100-108
Sera collected from cultured rainbow trout Oncorhynchus mykiss surviving outbreaks of infectious hematopoietic necrosis (IHN) or viral hemorrhagic septicemia (VHS) were examined for the presence of antibodies to both of the causative viruses, infectious hematopoietic necrosis virus (IHNV) and Egtved virus (viral hemorrhagic septicemia virus: VHSV). Sera were screened with...
Origins of acid fluids in geothermal reservoirs
Alfred Truesdell
1991, Conference Paper, Transactions - Geothermal Resources Council
Acid fluids in geothermal reservoirs are rare. Their occurrence in geothermal systems associated with recent volcanism (Tatun, Sumikawa, Miravalles) probably indicates that the geothermal reservoir fluid was derived from volcanic fluid incompletely neutralized by reaction with feldspars and micas. Superheated steam containing HCl (Larderello, The Geysers) forms acid where it...
Late Neogene marine Ostracoda from Tjornes, Iceland
T. M. Cronin
1991, Journal of Paleontology (65) 767-794
On the western side of the Tjörnes Peninsula in northern Iceland exposures of fossiliferous marine sediments, basalts, and glacial tills record the climatic history of this region of the North Atlantic Ocean. Seventy-five marine ostracode species were recovered from the Pliocene Tjörnes sediments and Quaternary sediments known...
Re - Os isotopic constraints on the origin of volcanic rocks, Gorgona Island, Colombia: Os isotopic evidence for ancient heterogeneities in the mantle
R.J. Walker, L.M. Echeverria, S.B. Shirey, M.F. Horan
1991, Contributions to Mineralogy and Petrology (107) 150-162
The Re - Os isotopic systematics of komatiites and spatially associated basalts from Gorgona Island, Colombia, indicate that they were produced at 155??43 Ma. Subsequent episodes of volcanism produced basalts at 88.1??3.8 Ma and picritic and basaltic lavas at ca. 58 Ma. The age for the ultramafic rocks is important...
Tektites in Cretaceous-Tertiary boundary rocks on Haiti and their bearing on the Alvarez impact extinction hypothesis
G. A. Izett
1991, Journal of Geophysical Research (96) 20879-20905
Relic tektites are associated with a Pt-group metal abundance anomaly and shocked minerals in a thin marl bed that marks the K-T boundary on Haiti. The presence of these three impact-produced materials at the precise K-T boundary enormously strengthens the Alvarez impact extinction hypothesis. The tektites...
An AEM-TEM study of weathering and diagenesis, Abert Lake, Oregon: II. Diagenetic modification of the sedimentary assemblage
J.F. Banfield, B.F. Jones, D.R. Veblen
1991, Geochimica et Cosmochimica Acta (55) 2795-2810
This paper compares the mineralogy and chemistry of clay minerals in sediments from various depths and positions in Abert Lake and surrounding playa with those of the weathered materials entering the lake in order to reveal the nature and extent of post-depositional mineralogical modification.Analytical electron microscope (AEM) data from individual...
Rare Plant Monitoring and Management at Point Reyes
Gary M. Fellers, Virginia Norris
1991, Park Science (11) 20-21
Capture myopathy in an endangered sandhill crane (Grus canadensis pulla)
J. W. Carpenter, Nancy Thomas, S. Reeves
1991, Journal of Zoo and Wildlife Medicine (22) 488-493
Despite precautions to protect cranes, a 3-year-old endangered Mississippi sandhill crane (Grus canadensis pulla) was found caught in a leghold trap in Gautier, Mississippi, on 11 November 1987. The bird could have been in the trap for up to 16 hr and was standing and struggling to escape when it...
Responses to in vitro and in vivo immunisations with Aeromonas salmonicida O antigen bacterins in rainbow trout (Oncorhynchus mykiss)
Douglas P. Anderson, G. Jeney
1991, Fish and Shellfish Immunology (1) 251-260
Immunological assays were developed to test for the effects of immunisation with Aeromonas salmonicida O antigen bacterin in rainbow trout (Oncorhynchus mykiss) in vitro and in vivo. Trout spleen sections were immunised in vitro by incubation in media containing 100, 10, and 1 μg ml−1 of the A. salmonicida O antigen. After 10 days at 15°C, the individual sections were minced...
Capture zones for simple aquifers
Carl D. McElwee
1991, Ground Water (29) 587-590
Abstract. The protection and cleanup of aquifers is a matter of high priority for all states and the federal government. One concept that is receiving increased attention is that of wellhead protection. Capture zones showing the area influenced by a well within a certain time are...
Some Nd and Sr isotopic systematics for the REE-enriched deposit at Bayan Obo, China
J. Philpotts, M. Tatsumoto, X. Li, K. Wang
1991, Chemical Geology (90) 177-188
Sm/1bNd and Rb/1bSr isotopic systematics have been determined for rare-earth element (REE) rich samples of carbonate, iron ore, and silicate types from the world's largest known REE deposit at Bayan Obo, China. The results yielded neither Rb/1bSr nor Sm/1bNd isochrons within analytical error. Isochronous relationships may have been disturbed in...
Petrography of Permian “Gondwana” coals from boreholes in northwestern Bangladesh, based on semiautomated reflectance scanning
Neely Bostick, William J. Betterton, Harold J. Gluskoter, Islam M. Nazrul
1991, Organic Geochemistry (17) 399-413
Drilling through Quaternary alluvium and Tertiary cover at low-gravity anomalies in northwestern Bangladesh showed the presence of Permian sedimentary rocks in depressions that may be as much as a thousand meters deep in the crystalline basement. These Permian strata include low-sulfur, high-volatile bituminous coals in beds as thick as 15...
Major element, REE, and Pb, Nd and Sr isotopic geochemistry of Cenozoic volcanic rocks of eastern China: Implications for their origin from suboceanic-type mantle reservoirs
A. R. Basu, Junwen Wang, Wankang Huang, Guanghong Xie, M. Tatsumoto
1991, Earth and Planetary Science Letters (105) 149-169
Major- and rare-earth-element (REE) concentrations and UThPb, SmNd, and RbSr isotope systematics are reported for Cenozoic volcanic rocks from northeastern and eastern China. These volcanic rocks, characteristically lacking the calc-alkaline suite of orogenic belts,...
Geochemistry of a Tertiary sedimentary phosphate deposit: Baja California Sur, Mexico
D.Z. Piper
1991, Chemical Geology (92) 283-316
The San Gregorio Formation in Baja California Sur, a phosphate-enriched sedimentary unit of late Oligocene to early Miocene age, has been analyzed in two areas (La Purisima and San Hilario) for its chemical composition (major oxides, Cu, Cd, Cr, Co, V, and rare-earth elements - REE) and isotopic composition (??18O...
Male sex steroids and hormonal control of male courtship behavior in the yellow-bellied slider turtle, Trachemys scripta
W.R. Garstka, W.E. Cooper Jr., K.W. Wasmund, J.E. Lovich
1991, Comparative Biochemistry and Physiology, Part A: Molecular & Integrative Physiology (98) 271-280
Survey of androgens and estrogens in serum, liver and testes of male yellow-bellied slider turtles, Trachemys (= Pseudemys) scripta, a species exhibiting dissociated gametogenesis age-dependent melanism, revealed the presence of numerous androgen precursors, androgens, androgen metabolites, and estrogens in quantities varying with season, tissue, and male coloration.The most commonly found...
Trondhjemitic, 1.35-1.31 Ga gneisses of the Mount Holly Complex of Vermont: evidence for an Elzevirian event in the Grenville Basement of the United States Appalachians
N. M. Ratcliffe, J. N. Aleinikoff, W.C. Burton, P. Karabinos
1991, Canadian Journal of Earth Sciences (28) 77-93
A newly recognized suite of trondhjemite–tonalite and dacitic gneiss forms a 10 km wide belt of rocks within the Mount Holly Complex in the central part of the Green Mountain massif of Vermont. Field relationships and chemistry indicate that these gneisses are calc-alkaline, volcanic, and hypabyssal plutonic rocks older than the...
Birds of the Kilbuck and Ahklun mountain region, Alaska
Margaret R. Petersen, Douglas N. Weir, Matthew H. Dick
1991, Report
Between 1952 and 1988, we studied the abundance, distribution, occurrence, and habitats used by birds in the northwest portion of Bristol Bay and the adjacent Kilbuck and Ahklun mountains. In the 809 days we were present, we conducted 53 studies or surveys of birds in the region. We gathered...
Geology of the Bayan Obo iron-rare-earth-niobium deposits, Inner Mongolia, China
L.J. Drew, M. Qingrun, S. Weijun
Anon, editor(s)
1991, Conference Paper, Preprint - Society of Mining Engineers of AIME
The plate tectonic setting, regional geology, and certain aspects of the economic geology of the iron-rare-earth-niobium ore bodies at Bayan Obo, Inner Mongolia, China, were studied by a team of geologists from the Tianjin Geologic Research Academy and the U.S. Geological Survey between 1987 and 1989. These ore bodies were...
