Alteration diagenetic

Concerns that diagenetic alteration could affect measured °Th ages of corals have existed since the early applications using alpha-counting methods. Thurber et al. (1965) offered the following list for reliable coral °Th ages a) no evidence of recrystallization, b) uranium concentration of 3 ppm, c) p°Th/ Th] of > 20, d) of 1.15 ... 

When dating corals, there are two results when Equations (1) and (2) are solved the °Th age and the initial value. If all corals remained closed to diagenetic alteration,... 

While many models have been proposed for changes in uranium-series isotopic composition with diagenetic alteration (e.g., Hamelin et al. 1991), documentation of a... 

Hedges, R. E. M. and A. R. Millard (1995b), Measurements and relationships of diagenetic alteration of bone from three archaeological sites,. Archaeol. Sci. 22, 201-209. 

In this chapter we consider how reaction modeling applied to open systems might be used to study the nature of diagenetic alteration. We develop examples in which modeling of this type can aid in interpreting the diagenetic reactions observed to have occurred in sedimentary rocks. 

Harrison (1990) proposed that the diagenetic alteration observed in the Latrobe group resulted from the mixing within the formation of two types of groundwaters. Table 25.1 shows analyses of waters sampled from two oil wells, which she took to be representative of the two water types as they exist in the producing areas of the basin. 

To test whether the mixing hypothesis might explain the diagenetic alteration observed, we begin by equilibrating the fresh water, assuming equilibrium with the potassium feldspar ( maximum microcline in the database), quartz, and muscovite (a proxy for illite) in the formation. In REACT, we enter the commands... 

J.W. Louda, J.W. Loitz, D.T. Rudnick and E.W. Baker, Early diagenetic alteration of chloro-phyll-a and bacteriochlorophyll-a in a contemporaneous marl ecosystem Florida Bay. Org. Geochem. 31 (2000) 1561-1580. 

Aromatization of hopanoids, when derived from bacterial detritus in sediments, is inferred to proceed via diagenetic alteration or bonding of the precursors to organic matter (e.g. diploptene to neohopene. 

MITSUI (K.), 1975. Diagenetic alteration of some minerals in argillaceous sediments in western Hokkaido, Japan. Science Rep. Tohoku Univ. 

VAN MOORT (J.C.), 1971. A comparative study of the diagenetic alteration of clay minerals in Mesozoic shales from Papua, New Guinea, and in Tertiary shales from Louisiana, U.S.A. Clays and Clay Min. 19, 1-20. 

Case studies from the Andes and Tibet show how these methods can be used alone or in combination to estimate paleoelevation. In both cases, the potential for diagenetic alteration... 

Cowie, G. L., and J. I. Hedges. 1994. Biochemical indicators of diagenetic alteration in natural organic matter mixtures. Nature 369 304-307. 

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