USING GEOCHEMICAL COMPOSITION TO INVESTIGATE SEDIMENT PROVENANCE AND PRODUCTIVITY IN ROCKS FROM CENTRAL KANSAS, USA

Paleo environmental conditions and sediment characteristics are not well constrained for stratigraphic units associated with some small fields within the Central Kansas Uplift. Samples of drill cutting recovered from a well, Hottmans #1, at 10 ft intervals between 3150ft and 3900ft below ground level, were processed and analyzed using X-ray fluorescence (XRF) and X-Ray diffraction (XRD). The XRF technique was used to determine elemental compositions, and XRD was used to determine mineral content. The composition of the rock cuttings was used to characterize sediments and assess paleo-conditions and provenances.

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.