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January 2012

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Timothy D. Bechtel, Ph.D., P.G. 1, Chet Hedden, Ph.D. 2, J.D. Mizer 3, Ute Bellmann 4, Sarah Truebe 3, Kenneth Destrang 3, Ellen Bechtel 5 1Franklin and Marshall College, Lancaster, PA, USA; 2Cave Research Foundation, Tuscon, AZ, USA; 3University of Arizona, Tuscon, AZ, USA; 4Karlsruhe Institute of Technology, Karlsruhe, Germany; 5Wellesley College, Wellesley, MA, USA Background and PurposeAt least two cave explorers recall accessing a significant underground river through a crawlway beneath a ledge in Swinnerton Avenue on the upper level of the Mammoth Cave system just southwest of the Duck-Under on January 2 and March 19, 1960 (see Figure 1). Recent expeditions to Swinnerton Avenue (in the 1980s and 2000s) failed to find this crawlway. Instead, the rock ledge in the area where the explorers recall the crawlway is at or only slightly above the level of sediment in the passage. Previous expeditions in 2007 and 2010 failed to find the crawlway, but did identify sediment transport features (ripple marks with gypsum fluff in the troughs, and gravelly rills; see Figure 2). However for sedimentation to have concealed the crawlway, it must have occurred between the 1960s and 1980s, and cosmogenic dating of sediments at the level of Swinnerton indicates that they have been underground for about 2.5 million years (Granger et al, 2001). In addition, according to records of the USGS gauging station BRKN2 just south of Mammoth Cave at Brownsville, KY, the largest flood since 1905 occurred on January 24, 1937 and raised the Green River 44.94 feet above normal pool (NOAA, 2013). This is far less than the 200 or more foot rise (Palmer 1981) necessary backflood Swinnerton Avenue. However, the authors have observed recent organic material in passages just below Swinnerton in 2003, 2007, and 2010, as well as flowing water in a narrow (impassable) channel obliquely crossing Swinnerton north of the Duck-Under, suggesting open channel flow of infiltrating surface water. Such flow, particularly if it is intense during and/or after storm events could have moved sediments within the cave. Alternatively localized aeolian sediment transport within the upper levels of Mammoth may be indicated by a famous set of "dunes" in Turner Avenue, and by the preferential occurrence of gypsum fluff in the troughs of ripple marks as observed in Swinnerton itself (Figure 2). The purpose of this investigation was to determine whether there is evidence in Swinnerton of recent sediment transport that could explain the apparent disappearance of the entrance to the "Lost River". In addition, while preparing for this study, the authors became aware of the "Three Springs Conundrum" formulated by Meiman et al (2001) based on dye tracing that showed that the disappearing stream fed by Three Springs has not been found underground, and that shallow and deep flow pathways may go in different directions. The volume and direction of flow in the "Lost River" as recalled by early explorers even before formulation of the Conudrum is consistent with a likely explanation for the Conundrum - that is, the Lost River is in the right place and flowing the right direction to represent the swallowed Three Springs water. Thus, a second complementary purpose became collection of data that might indicate the path taken by water that emerges at Three Springs, and is quickly lost again into the Mammoth plumbing system. Open Access - Permission by Author(s) See Extended description for more information.

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K26-01559

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