USING GEOCHEMICAL COMPOSITION TO INVESTIGATE SEDIMENT PROVENANCE AND PRODUCTIVITY IN ROCKS FROM CENTRAL KANSAS, USA
Cross plots of detrital proxies Ti, Al, K, and Zr show a strong positive relationship, which account for about 30% of the total elemental composition. Carbonate proxies, Mg, Ca and Sr, show strong positive correlations with each other indicating a common source, and collectively account for 70% elemental composition. This observation supports XRD data that shows that the analyzed interval is mainly carbonate with minor amounts of detrital inputs. Phosphorous, a measure of paleo-productivity ranged from 0.18% to 0.36% with a mean of 0.25%, well above crustal abundance of 0.01%. This significant enrichment of P is interpreted to indicate relatively high paleo productivity. This is supported by a strong positive correlation between P/Al and Ca/Al, as Ca is associated to presence of carbonate shelled organisms. An analysis of downhole variation in Zr/Rb ratio revealed two distinct zones. The first zone from 3150 to 3400 ft below ground level showed a mean Zr/Rb ratio of 1.80 ± 0.26. The second zone ranged from 3400 to 3850 ft with a mean Zr/Rb ratio of 1.44 ± 0.21. Based on these Zr/Rb ratios, the first zone is interpreted to be finer grained compared to the second zone, suggesting a characteristic fining upward sequence in the interval.