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| 60 | A t the invitation of L. G. Straus and M. González Morales, I began sedimentological study of El Mirón in 1997. The objectives of this study were the description of the sediments enclosing the archaeological finds, understanding their stratigraphic relations, deciphering their origins and paleoenvironmental settings, and ultimately evaluating the role of sediments in reconstructing human cultural activities in and around the site. The philosophical approach and methodology in this study follow those of W. R. Farrand (2001), adapted as necessary to the idiosyncratic aspects of this particular site. Fieldwork general The studies reported here are based on field observations in 1997, 1998, 2000, and 2002 by the author, with the assistance of William Hubbard in the field in 2000. In each of these seasons we examined the sections exposed by the excavation team and selectively sampled the strata following the identifications of the excavators. Also, Hubbard and I excavated a geologic trench partway up the ramp (“colluvial slope,” as described by Straus [chap. 3, this volume]) that leads from the vestibule up into the dark inner cave. No archaeological remains were found in the ramp sediments, which were poorly sorted, heterogeneous fluvial deposits (plate 5.1). In addition, we explored the surrounding area for evidence of sources of sediment external to the cave, possible river terraces, and related geomorphic features. We were guided in the latter effort by Enrique Serrano, then of Universidad de Cantabria, who was studying the glacial history of the upper Río Asón and the eastern Cantabrian Cordillera. Of special interest was Cuevamur, a cave near El Mirón with a sedimentary fill similar to the older sediments in El Mirón. ChAPter FiVe sedimentology of el mirón Cave William R. Farrand Sedimentology of El Mirón Cave | 61 | was labeled with the number of the stratum and the square from which it was collected and in some cases with the addition of “upper,” “mid,” or “lower” to indicate multiple samples from a given stratum. Samples commonly weighed between 100 g and 1000 g, with larger samples from beds of coarser sediment . In most cases the Munsell color of the sampled sediment was recorded in the field under moist conditions .Theremainderwerecolor-codedinthelaboratory under dry conditions, as noted in table 5.1. The moisture content was measured upon arrival in the laboratory, only a few weeks after the samples were collected. They had been wrapped in double plastic bags that preserved the original moisture state reasonably well. The remainders of these samples are archived in the Museum of Anthropology at the University of Michigan. sampling Seventy-seven stratigraphic samples, listed in table 5.1, were collected from the Cabin, Mid-Vestibule, Corral, and Footslope excavation areas of the sunlit vestibule, as well as from the Trinchera in the dark, inner cave and from the ramp. Miscellaneous samples included pieces of the cave bedrock and terra rossa soil from outside the cave. The samples were shipped to the University of Michigan for analysis. Samples were selected by visual inspection of the exposed strata in the excavated areas with the goal of taking at least one sample from each archaeological stratum or two or more samples if the stratum was rather thick or seemed to include some internal variation. In a few cases a given stratum was resampled in successive seasons or in different excavation squares to evaluate lateral variations. Each sample methodology granulometry The samples were dried and weighed again during initial processing in the laboratory. Then various fractions were separated for further analysis. The coarse fraction, from 128 mm to 10 mm, was measured by hand. The sand and granule fraction, 10 to 0.063 mm, was sorted by wet sieving, and the finest fraction was measured with a Spectrex™ laser counter, with verification of some samples by a Coulter™ counter. In addition, Hubbard (2000, figs. 12–15) determined the granulometry of the fine fraction after decalcification with 10 percent HCl and mild heating. roundness The degree of rounding of the larger clasts—that is, the extent of rounding of originally angular corners of the rock fragments—was observed visually and indexed according to the system of W. R. Farrand (1975, 2001). Clasts of a selected size range, in this case between 8 mm and 32 mm, were classified as follows: • Class 0: only angular corners and edges; no rounding • Class 1: more angular corners and edges than rounded ones—subangular • Class 2: more rounded corners than angular ones—subrounded • Class...

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