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ll • south of Pueblo, within Tract "B" of the proposed RGPCC quarry site. Such high carbonate /low non-calcareous percentages could be evidence of a distal paleogeographic position from the western shoreline of the seaway for the Huerfano Park area and Rock Canyon Anticlinorium. An upsection trend towards higher CaCOy percentages in the - shale intetbeds, with the most prominent increases occurring at or near the datum line, can be observed in all 3 sections. Further, this upwards increase in carbonate is mirrored by increasingly negative isotopic oxygen values (a trend best developed at Wolcott), interpreted as a microplanktonic response to steadily warming paleoceanographic conditions within the Western Interior seaway. The fluctuations in C°tg through each shale-limestone couplet in the tower Fort Hays Member is somewhat cyclic in nature, as can be seen in the record from Wagon Mound (having two samples per bed). These variations, however, rarely exceed 0.5 between successive samples. In contrast, the globally-recognized Honarelli Anoxic Event which encompasses the Cenomanian-Turonian stage boundary, has yielded Cars values as high as 4.5% and variations between successive samples of similaz magnitude (Pratt, 1985). Evidence has been presented for aworld-wide oceanic anoxic event (OAI:) during the Coniacian (Arthtu el a[., 1990; Jenkyns, 1991), but this relatively short-term event was largely restricted [o the Late Coniacian, thereby having little beating on the deposition of the Fort Hays Member. Were there an anoxic episode in the Western • Interior during deposition of the FoR Hays, then Cora values greater than 1.0 % (by weight) would be expected from the shale intetbeds. As it is, only a single sample reached organic carbon levels of 1.0 % (shale 5.5, Wolcott section). Black, laminated, organic-rich shale from the upper part of the lower shale unit (Smoky Hill Member), -6 m above the top of the Fort }Iays Member, likely correspond to the purported anoxic event. The piettue presented by carbon and oxygen isotopes is more complex than that from total organic cazbon. In terms of magnitude of perturbation(s) between successive samples, especially between shales and limestones, the isotopic data produced from this study only marginally qualify as significant towards paleoecological interpretations and reconstructions. Great taution was used in making inferences based on attained isotopic oxygen and isotopic cazbon values. The average, or "background" isotopic carbon signal for the Turonian through Santottian of the Westcm Interior is approximately +1.0 ppm (shown by vertical line in Figs. 7 & 8, and background isotopic oxygen levels approach -6.0 ppm. Limestone beds of the lower Fort Hays Member generally tend to be more depleted !lighter in isotopic carbon than shale intetbeds, and ofren have slightly heavier • zoot