2002-07-03_PERMIT FILE - M2002004

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• EXHIBIT D - MINING PLAN GEOLOGY The Fort Hays Limestone Member (Niobrara Formation) was deposited in a shallow seaway which covered the Western Interior of North America during the Late Cretaceous period. (approximately 88.0 million years ago). The distribution of the characteristic interbedded white to light gray limestones and dark gray shale interbeds was controlled to a large extent by distance from the western shoreline of the ancient Cretaceous seaway. Over the course of hundreds of thousands of years the accumulated skeletons of calcium carbonate-secreting planktonic microorganisms (e.g. calcareous nannofossils) formed the nearly pure limestone visible in numerous outcrops surrounding the City of Pueblo. As these microscopic animals required relatively clear, sunlit seawater to survive, the limestone-dominated belt of the Fort Hays does not extend as far west as the position of the "paleobeach." The location of these ancient shoreline deposits ( in the vicinity of present day east-central Utah) is an area dominated by sandstone and mudstone rocks, with no limestone. The most westerly outcrop of the Fort Hays Limestone is at Newcastle, CO - a locality having no pure limestone beds due to the high amount of mud and silt from the western sediment source area. The Fort Hays Limestone at the project site in Pueblo County, in contrast, is predominantly pure limestone, with very thin shale interbeds. The general strike of the limestone is N49°W at a dip of approximately 2°NE The shales are free of excessive quantities of pyrite and associated sulfide minerals, due to the well-oxygenated nature of the seafloor during deposition of the Fort Hays; therefore, the area immediately southeast of Interstate I-25 that has been drill core sampled and tested by Rio Grande contains much less organic carbon-bearing, fine-grained mud rock than the foothills to the west, an . observation easily verified by visual analysis of the numerous Fort Hays cores presently archived in Pueblo. Agrochemical testing of these limestones (from Rio Grande lands) indicates that they contain some of the lowest concentrations of kerogens and sulfur-based by-products of any carbonate rock presently used as a resource by the cement industry in Mexico, Canada, and the United States. Findings of the August 2000 geologic report (Appendix J) by Christopher J. Collom, PhD, are summarized in the following four main points: The proposed Rio Grande plant/surface mine site in Pueblo County, Colorado is within the "central limestone-dominated" belt of the Fort Hays Member (in terms of the total geographic distribution of the Fort Hays Member); in contrast, at least two cement operations in Colorado are located in and utilizing less pure Fort Hays resources from the "western argillaceous-dominated" belt. 2. Relative to the western shoreline of the Late Cretaceous-age seaway (that covered essentially all of Colorado during the deposition of the Fort Hays Member), the proposed Rio Grande site is sufficiently distant from the prevailing sediment-supply to avoid contamination by siliciclastic muds (thus, the majority of the sediments observed are detritus-free limestones) - additionally, north to south geostrophic ("longshore") currents along the western shoreline of the seaway, documented from abundant stratigraphic evidence (in Colorado, Wyoming, Montana, and Utah) "buffered" the offshore regions of the Western Interior (=central limestone-dominated belt) from river-born plumes of fine-grained detritus. 3. The position of the proposed Rio Grande surface mine on the Trans-Continental Arch basement • structure (actively uplifted during the Late Cretaceous) provided additional condensation of sediments during the deposition of the Fort Hays Member, and effective bypass or removal of 1180-Mine Permit Exhibits (Jul.03.02)FINAL.doc D-1 July 3, 2002