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Thermoluminescence Dating of Hawaiian Basalt - Usgs Professional Paper 1095 (Paperback)
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Discovery Miles 4 640
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Thermoluminescence Dating of Hawaiian Basalt - Usgs Professional Paper 1095 (Paperback)
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Loot Price R464
Discovery Miles 4 640
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The thermoluminescence (TL) properties of plagioclase separates
from 11 independently dated alkalic basalts 4,500 years to 3.3
million years old and 17 tholeiitic basalts 16 years to 450,000
years old from the Hawaiian Islands were investigated for the
purpose of developing a TL dating method for young volcanic rocks.
Ratios of natural to artificial TL intensity, when normalized for
natural radiation dose rates, were used to quantify the
thermoluminescence response of individual samples for
age-determination purposes. The TL ratios for the alkalic basalt
plagioclase were found to increase with age at a predictable
exponential rate that permits the use of the equation for the
best-fit line through a plot of the TL ratios relative to known age
as a TL age equation. The equation is applicable to rocks ranging
in composition from basaltic andesite to trachyte over the age
range from about 2,000 to at least 250,000 years before present
(B.P.). The TL ages for samples older than 50,000 years have a
calculated precision of less than: t 10 percent and a potential
estimated accuracy relative to potassium-argon ages of
approximately: t 10 percent. An attempt to develop a similar dating
curve for the tholeiitic basalts was not as successful, primarily
because the dose rates are on the average lower than those for the
alkalic basalts by a factor of 6, resulting in lower TL intensities
in the tholeiitic basalts for samples of equivalent age, and also
because the age distribution of dated material is inadequate. The
basic TL properties of the plagioclase from the two rock types are
similar, however, and TL dating of tholeiitic basalts should
eventually be feasible over the age range 10,000 to at least
200,000 years B.P. The average composition of the plagioclase
separates from the alkalic basalts ranges from oligoclase to
andesine; compositional variations within this range have no
apparent effect on the TL ratios.
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