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SENT BY~FSP&T, LLC, 02 ;11-20- 1 ~30AM ~ FSP&'I', LLt, uz-~ ~u~ ret azao;~ x/14 <br /> ~FCEIV~~ <br /> <br /> <br /> INTRODUCTION •:~ ~~~;,;;,;;., :- .-„~._ <br />STATiGM1.;AY $OOn'CES,FRCG <br />i <br />;' <br /> <br />• - . <br />. <br />. <br />D <br />i <br />h <br />C <br />i <br />d <br />100 <br />U <br /> ur <br />ng t <br />retaceous Per <br />o <br />( <br />e <br />pper <br />-80 million years ago) sea level was <br /> more than l50 metres above present levels, forming an elongate epicontinental seaway <br /> throughout the west-central portion of the United States and Canada. This is a time when <br /> the state of Colorado and surrounding regions were relatively low-]ying, prior to the <br /> major uplift that formed the present Rocky Mountains. Though rarely more than 1,500 <br /> km in width, deposits of the Western Interior seaway are represented over a fourteen state <br /> / four province area, and reach thicknesses in excess of 1.5 km. The major source of <br /> clastic (non-carbonate) sediment input into the seaway was along the extensive western <br /> shoreline, which over time formed an asymmetric sedimentary basin. The thicker and <br /> coarser-grained portion of this sedimentary sequence-was deposited neaz the western edge <br /> of the basin, whereas thinner near-pure time muds were deposited within the central and <br /> eastern portions of the Western Interior seaway (Figure 2). The lithologies resulting from <br /> deposition of these carbonates were extremely fine-grained, well-indurated to chalky <br /> limestones, separated by thinner dark calcareous shales. This report focuses on a single <br /> ~30 m thick portion of the Upper Cretaceous rock record in Colorado: the Fort Hays <br /> Member of the Niobrara Formation. The limestones of the Fort Hays Mbr display <br /> remarkable lateral persistence, with individual beds laterally correlative for distances up <br /> to 500 km (Collom, 1991). Separating the limestone beds ate considerably thinner <br />• calcareous shale interbeds, that are thicker in the "western facies belt" and thin to <!.0 <br /> cm in eastern Colorrdo(Figure 2), <br />Formally named by B.F. Mudge in 1876, the Fort Hays Limestone Member has <br />been known in some detail for more than a century (Hattie, 1982). It was not until the <br />work of Williston (1893}, though, tha[the Fort Hays was used in it's modem stra[igtaphic <br />definition, except that Williston included the unit in the Benton Formation rather than the <br />Niobrara. Despite being one of the earliest described rock formations. in the American <br />West (Meek & Hayden, 1861), the lower Niobrara Formation continues to present many <br />challenging and unanswered questions to the geologist and paleontologist. <br />Stratigraphically the tower and more resistive of the two members of the Niobrara <br />Fmn (below the thicker and more widespread Smoky Hi11 Chalk), the Fort Hays <br />Limestone typically outcrops along hogbacks and supports steep embankments upon <br />exposure. The type section and locality is along the Smoky Hill River near Hays, Ellis <br />County, wes[ertt Kansas. The Fort Hays Member extends across a six state area, but the <br />most well exposed and complete sections of the Fort Hays are in western Kansas (as <br />• tv~a <br />