Dating Uncertainties with Thermoluminescence
Larry A. DeWerd
Thermoluminescence is the emission of light from a solid material that has received a dose from radiation. This phenomenon can be used to date pottery and volcanic eruptions, since the luminescence increases as it is irradiated with time to the point of saturation. The amount of radioactivity in the vicinity of the sample has to be measured, which can be one of the potential sources of error, since any change in the radioactivity of the past can affect the proposed date. The date obtained is dependent on the environment of the site where the sample is located. Other characteristics of the thermoluminescence process can affect the date obtained. The mechanism of thermoluminescence will be described using an alkali halide, LiF:Mg,Ti, as an example of potential sources of error. Alkali halides have been studied extensively for their use as a dosimeter in the medical radiation field. Careful control of the thermoluminescence can result in good accuracy. The thermoluminescence of quartz will be discussed. The criteria and assumptions necessary for the dating process and the potential problems will be described. The uncertainty of the process will be explained and how it may affect the date. Thermoluminescent measurements, when all uncertainties or the process are accounted for, show dates less than 6000 years. A review of the thermoluminescence process shows that this is a useful area of research for the creation scientist.
A Little Flood Geology Part III: A False Dilemma
Floods are a key category of geologic processes. Parts I and II of this series provided some examples of geologic work by floods and related processes in Central Montana as witnessed by the author and how these may apply to the study of earth history. In Part III, geologic processes associated with these engineering projects are presented that are not flood processes. Evolutionists tend to overlook or resist evidence for catastrophic, large-scale processes (especially diluvial processes), while creationists can be tempted to overlook or downplay the role of smaller-scale processes that are presently active. This is a false dilemma, as these examples illustrate. The problem is one of philosophy and method, not of evidence.
Cyclostratigraphy and Astrochronology Part IV: Is the Pre-Pleistocene Sedimentary Record Defined by Orbitally-Forced Cycles?
Michael J. Oard and John K. Reed
Cyclostratigraphy is a popular method that promises much more precise dates than biostratigraphy or radioisotope dating. Originally, it was pioneered to date Pleistocene glacial/interglacial intervals, but its reach has been steadily extended back through the Cenozoic and into earlier eras using sedimentary cycles. Unfortunately, enthusiasm for its potential has blinded geologists to its problems. Six problems are addressed, revealing the influence of subjective factors not commonly noticed.
The Johnnie Oolite: A Remarkable Early Flood Deposit in the Death Valley Region, California, USA
Cornelius Van Wingerden
The Johnnie Oolite bed is a significant and regionally widespread carbonate deposit exposed in the Death Valley region of the central Southern Great Basin of California, USA. Most modern oolitic deposits occur in warm waters off tropical and temperate regions such as the Bahama Islands. These are well studied and understood. Oolite deposits found in the geologic record leave some investigators perplexed. In ancient environments, mode of deposition, association with confining sediments, chemistry of sea water and the range, size, and development of ooid formation differ from modern exposures. The Johnnie Oolite bed, averaging 6 feet thick, is a carbonate grainstone composed mostly of ooids, peloids, and lithic fragments was deposited in a high energy environment. Several field exposures of the Johnnie Oolite were observed and investigated. It is stratigraphically bounded above and below by shale deposits. The ooids in the Johnnie Oolite bed are cross bedded and normal to inversely graded. In places, clasts of carbonate mud oriented edgewise are floating within the oolite bedding. In the Nopah Range, the upper middle oolite bed is disrupted and contains rip-up clasts, fluid escape structures, and an erosional bedding plane. These sedimentary structures, their relationship to the enclosing shale beds and the thin section analysis indicate rapid deposition by strong currents in a deeper marine environment, consistent with the earliest stages of the Noachian Flood. Johnnie Oolite grainstone is interpreted as a mass flow with physical properties of strength and competence and super saturated with CaCO3 . The ooids and peloids likely formed in transit after the breakup of the initial Fountains and the deposits of the Kingston Peak Fm and Noonday Dolomite. The Kingston Peak Fm is considered the initial Flood deposit in the study area.