Of Caves and Shell Mounds

4. Prehistoric Mining in the Mammoth Cave System

4 Prehistoric Mining in the Mammoth Cave System Kenneth B. Tankersley MORE THAN 100 years of archaeological investigations demonstrate that the Flint-Mammoth Cave system was explored prehistorically. Indeed, Putnam (1875), Young (1910), Nelson (1917), Pond (1935, 1937), and Schwartz (1960a) illustrate a wide range of perishable artifacts associated with prehistoric caving activity. Watson (1966, 1977, 1985b, 1986; Watson, ed., 1974; Watson et al. 1969), demonstrates that most of this exploration activity was carried out by Early Woodland peoples for the purpose of obtaining two types of cave mineralsgypsum and speleothem salt. In this chapter I focus on the prehistoric exploitation of speleothem salt, first describing the occurrence of these resources and the techniques used in their procurement. Evidence suggesting that Early Woodland peoples understood that speleothem salt is renewable, and that they took steps to exploit this phenomenon is presented. Finally, the implications of renewable mineral mining in the context of contemporary exploitive patterns in the Green River valley is discussed. Speleothem Salt Occurrence and Procurement Techniques Two forms of speleothem salt occur in the Mammoth Cave systemmirabilite (NaS04 lOH20 hydrous sodium sulfate, glauber salts), and epsomite (MgS04 7H20 hydrous magnesium sulfate, epsom salts). Mirabilite has a salty taste and is more common and widespread than epsomite in the areas of the Flint-Mammoth Cave system that were explored prehistorically (Watson 1966, 1977; Watson, ed., 1974; Watson and Yarnell 1966). My discussion concentrates on this resource. The procurement techniques of speleothem salt varied according to its habit, that is, the shape and relative proportions of the crystals. Mirabilite effloresces as both fibrous and massive crystals (Hill 1976:61-75). If the deposit occurred as delicate cottonlike "whiskers," then speleothem salt could have been brushed into a receptacle with a stiff feather, like those described by Putnam (1875) and Young (1910:316). If the deposit occurred as needles protruding from sulfate-saturated alluvium, then the salt-rich sediment was likely excavated with the aid of a digging stick (Munson et al. 1989; Young 1910:317). If the de33 34 I Kenneth B. Tankersley posit occurred as a crust or series of flowers, then stone and shell tools were probably used to scrape the salt from the cave walls (Watson et al. 1969:59, 61). Because of their chemical and textural similarity, mirabilite and gypsum frequently co-occur (Watson 1966:242; Watson and Yarnell 1966:847; White 1969:79-82). In this form, speleothem salt falls from exfoliating cave walls and ceilings. Undoubtedly, large chunks of this material were procured by hand. In its purest crystalline state, mirabilite is soluble and dehydrates when exposed to surface air (Hill 1976:65). Speleothem salt, however, retains its salty properties in most surface environments (Watson and Yarnell 1966:847). Opportunistic and Systematic Mining The earliest form of speleothem salt mining was perhaps strictly opportunistic . As the first prehistoric cavers explored the dry upper levels of the FlintMammoth Cave system, they would have encountered sparkling white speleothem salt on walls, ledges, breakdown, and alluvial surfaces (Figures 4.1 and 4.2). In certain areas, such as the Snow Room in Mammoth Cave and the area just north of Grand Forks in Salts Cave, the salt is so concentrated that the aboriginal cavers must have literally tasted it in the air as one does today. It seems reasonable to assume that subsequent salt procurement would have continued to be opportunistic, but also systematic. Assuming a "least cost" mining attitude, speleothem salts located closest to cave entrances would have been procured first, and those deposits located farthest from entrances would have been procured last. Aside from the excitement of exploring the underground world, the exploitation of speleothem salt may have been the early driving force behind the exploration of the Flint-Mammoth Cave system (Watson 1985b:152; Watson 1966:242; Watson et al. 1969:57). Given the fact that the suite of radiocarbon dates associated with prehistoric activity in the Flint-Mammoth Cave system spans more than 2,000 years (Kennedy , this volume; Watson, ed., 1974:236-37), two archaeological and geological assumptions can be made concerning speleothem salt procurement: (1) speleothem salt regenerates in areas of the cave that were previously mined, and (2) Early Woodland miners noticed this phenomenon. Some of the mining sites that were stripped of salt one year would have been entirely replenished during the following season. Mirabilite grows relatively rapidly, in a matter of months (Hil11976:65). This regrowth usually occurs during the damp months of late winter and early spring...