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ANALYSIS OF SIGNIFICANCE EVALUATION CRITERIA The boundary study criteria contained in the National Park Service Management Policies (Chapter 2:8), states that "The National Park Service will conduct studies of potential boundary adjustments and may recommend boundary revisions to include significant resources or opportunities for public enjoyment related to the purposes of the park; address operational and management issues such as access and boundary identification by topographic or other natural features or roads; and protect park resources critical to fulfilling the park's purposes. The latter two criteria are not applicable to this study since there was not a situation where there was a related issue. Primary justification for expanding the boundary woold be to include significant resources and opportunities for public enjoyment related to the purpose of the park." The "purpose" of BLCA is stated in Presidential Proclamation No. 2033 dated March 2, 1933, which established the area. This document cites the purpose as being "...for the preservation of the spectacular gorges and additional features of scenic, scientific, and educational interest. Those resources and opportunities within the study area determined to be significant in relation to the purpose of the monument and of scientific and public interest follow. SIGNIFICANT FEATURES Geological Values Renowned geologist, Wallace R. Hansen, has thoroughly studied the lower gorge area and offers the following comments on its character. "This reach of the canyon shares many of the attributes of the monument, but in many ways, it is much different, particularly with respect to the sedimentary cap rocks, which are poorly exposed in the monument but are exceptionally well exposed downstream. These rocks, Jurassic and Cretaceous in age, add a scenic and geologic aspect to that part of the canyon that is essentially nonexistent in the monument. "Both sections ofthe canyon, however, are integral parts of one huge physiographic entity and they complement one another rather than compete. Neither section alone tells the whole story. The whole Black Canyon is truly a world-class gorge, among the best that America has to offer the visiting public, and the geologic story is incomplete without reference to its downstream section. "One of the most significant geologic attributes of the downstream section of the canyon is the extent and display of large-scale faulting and the relationship of faulting to the geologic history of the Gunnison uplift and the canyon itself. This concept may at first 15