MINERALOGICAL ANALYSIS OF UPPER DEVONIAN BLACK SHALES IN WESTERN NEW YORK

Mineral composition and the percent of total organic carbon (TOC) in black shales of Dunkirk and Hume formations in western New York were determined by X-ray diffraction. Upper Devonian Black Shales of the Dunkirk and Hume Formations lie in the Upper Devonian Canadaway group. Dunkirk and Hume formations are potential source rocks for oil and gas-producing reservoirs. To examine the burial depth and temperature of the black shales, the extent of illite-smectite diagenesis was examined. Mineral composition of the black shales was determined quantitatively using the RockJock software to analyze the X-ray diffraction scans. TOC was analyzed with a CM 5120 TOC analyzer. The principal clay minerals in all the samples are chlorite and 2M1 illite. There is a modest inverse relationship between the percent of organic carbon and the weight percent of illite suggesting that the clay minerals have participated in hydrocarbon production. The degree of metamorphism experienced by the black shales was determined by measuring the Kübler index (KI), also based on the X-ray diffraction scans. Most samples had KI values corresponding to the transition from anchizone to epizone, though a few samples fall into the epizone. The highest temperatures, over 360°C may be related to large fractures in the black shale.