Spectral reflectance of conodonts: A step toward quantitative color alteration and thermal maturity indexes
- Texas Wesleyan Univ., Fort Worth, TX (United States)
- Univ. of Texas, Arlington, TX (United States)
Changes in the color of conodonts have long been used to assess thermal maturity. Color is a subjective measure, and color changes in conodonts are related to a subjective scale, the conodont alteration index or CAI. In this paper, we propose a simple, nondestructive method for objectively determining CAI and relating CAI to thermal maturity, the spectral reflectance of conodonts (SRC). The diffuse reflectance of about 30 large conodont fragments arranged on a barium-sulfate slide was determined with a total reflectance spectrophotometer in the wavelength range of 300-850 nm. By examining conodonts that ranged form a CAI of 1 to a CAI of 6 we found that the average slope of the reflectance curve from 550 to 800 nm is a good proxy for CAI. A second-order regression equation estimates CAI from this slope with high accuracy (correlation coefficient = 0.99). These estimates appear most accurate for a CAI of 1 to a CAI of 4, where the slopes change most rapidly, but give reasonable results up to a CAI of 6. Based on the results of our analysis of two samples with known thermal maturities form the Valles Caldera region of New Mexico, we propose a preliminary relationship among SRC slope, CAI, and in-situ alteration temperature.
- OSTI ID:
- 263027
- Journal Information:
- AAPG Bulletin, Vol. 80, Issue 7; Other Information: PBD: Jul 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Overburden and physical properties in the Marathon fold and thrust belt, West Texas, using conodont thermal maturity and vitrinite reflectance
Interpretation of conodont color alteration and thermal maturation in Amadeus basin, central Australia