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much as 30 meters thick), southeastem Colorado (IS m at its thickest), and ttortheastem • New Mexico (aver 17 m thick). The Fort Flays is known from several different Western Interior basins, which include the Salina Basin (south central Nebraska}, Dodge City Rosin (western Kansas), Denver-Julesburg Basin (eastern Colorado and southeastern comer of Wyoming), North and South park Basins (north-central Colorado), Raton Basin (southeastern Colorado and northeastern New Mexico), and Las Vegas Basin (norchem New Mexico). Throughout most of its extent, the Fort Hays Member unconformably overlies (has an erosional lower contact) four different members of the Carlile Formation: the Montezuma Valley Shale Member (formerly referred to as the "Sage Breaks equivalent"), Juana Lopez Member, Codell Sandstone Member, and the upper portion of the Blue Hil] Shale Member. Within the proposed RGPCC quarry site the Fort Hays Limestone uncgnfotmably overlies the Codell Member (the Juana Lopez and Montezuma Valley members are absent). The so-called "Shale and Limestone Unit" of Scott and Cobban (1964), located immediately above the Fort Hays Member, will be referred to in this report as the "Trans-Lime"; an informal term used in the cement industry in Colorado to describe the more shale-rich (less pure) beds of the lower Smoky Hill Member. The relatively more condensed nature of the Carlile Formation -Niobrara Formation contact in the Pueblo area is due to the underlying granitic basement rocks (more than I.5 billion • years old). The particular basement feature that was tectonically reactivated during the deposition of the various rock oohs listed above is the Trans-Continental Arch (Fig. 4). It's upward movement, measured on the scale of metres, was nevertheless sufficient to cause marine erosion of a significant portion of the overlying sediments, and lead to deposition of thinner shale interbeds within the Fort Hays Member. Yelagic basiaal sequences displaying rhythmic bedding Can be correlated, essentially bed-by-bed, over very long distances. In the Western Interior Cretaceous this is especially true for the Bridge Creek Limestone (Hattin, 1977) and Fort Hays Limestone. Laferriere (1987) achieved high resolution correlation most prominently at the 1 Z6 Kyr Tavel in the Fort Hays (exposure spacing of ~80 km), though this may or may not be a ret7ection of the eccentrieiry cycle. Correlation of individual limestone beds has proven difficult, given the amount of anastomosing & bifurcating of limestones that apparently does occur, but Collom (1991) has been able to precisely correlate the basal ten limestone beds over distances greater than 500 km (with average exposure spacing of 125 km). High-resolution work of this kind uti]ize all available marker beds, which in this instance include bentonitcs, shell lags, and macrofossil occurrences (Figure 5). • 1995