Source Area Analysis of Obsidian Flakes from a Lower Loup Phase Site in Nebraska

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Non-destructive energy dispersive x-ray fluorescence analysis was applied to obsidian flakes from 25LP8, a Lower Loup phase site in Nebraska. All flakes have the same trace element composition as volcanic glasses of the Cerro del Medio chemical type, located in the Jemez Mountains of northern New Mexico.

Keywords: obsidian, source analysis, Lower Loup phase

Recent studies of lithic raw material utilization in the Lower Loup phase (ca. 1550/1600-1803)i.e., by the Pawnee people during protohistoric period-have emphasized procurement strategies and their implications for land use (Holen 1983, 1991; Hudson 1982). These analyses quite properly are concerned with the predominant raw materials and not with the exotic (non-local) materials that comprise a small percentage of the collections. Vehik and Baugh (1994:263) and Roper (1994:63), however, have recently noted that very little is known about exchange relations during the Lower Loup phase. In this brief note, therefore, we place on record provenance data for obsidian recovered from a single Lower Loup phase site in east-central Nebraska, which we hope will contribute to a fuller understanding of sixteenth and seventeenth century exotic material conveyance patterns in the Central Plains.


The source analysis reported here was conducted on obsidian flakes recovered during extensive excavations in 1984 by the junior author at the Royel Goodnow site, 25LP8. Now inundated by Calamus Reservoir, Goodnow was an approximately 5 hectare hunting camp site on a terrace of the Calamus River in extreme eastern Loup County, Nebraska (Figure I ). It was attributed to the Lower Loup phase on the basis of the pottery and chipped stone artifact types (Roper 1989). Ludwickson and Tieszen (1996) recently disputed the Lower Loup phase identification and assigned the site to the Extended Coalescent variant, suggesting it is entirely unrelated to the Pawnee or other Northern Caddoan peoples. Roper, however, rejected their argument for reasons detailed elsewhere (Roper 1997). A radiocarbon age determination on charcoal from a hearth is 280+60 BP (Beta- 12,737). The calibrated 1sigma calendar date range is 1512-1598 or 1617-1671, with a slightly higher probability of the true date falling into the earlier range (calibrations made using Method B of Stuiver and Reimer 1993). Dates obtained using Grange's (1984) ceramic formula method range from 1610 to 1651, depending on the exact identification of several ambiguous vessel rims (Roper 1994:65). Either way, 25LP8 appears to have been a fairly early Lower Loup phase site.

The chipped stone element of the 25LP8 assemblage included 108 projectile points, 64 bifaces or biface fragments, 77 scrapers, 75 utilized flakes, 15 cores, and 27,755 pieces of unmodified debitage (Roper 1989:207-235). In total, 89.2% of all tools and 95.0% of the debitage were Republican River jasper; the remaining lithic toolstones included cherts, chalcedonies, quartzites, and obsidian. No finished artifacts were made of obsidian, but 25 flakes (0.1 %) were of this material. The majority of the obsidian flakes, 17 of 25, fell into the 5-IO mm size class. Four each of the remaining flakes were in the 0-5 and 10-15 mm size classes. All were found in a small area in the east-central part of the site. They appear macroscopically identical and may represent a single episode of reduction or maintenance of a nodule or tool. Four of the largest flakes were selected for source analysis (Table 1).


Laboratory investigations were performed by the senior author on a Spectrace(TM) 5000 (Tracor Xray) energy dispersive x-ray fluorescence spectrometer equipped with a Rh x-ray tube, a 50 kV x-ray generator, with microprocessor-controlled pulse processor (amplifier) and bias/protection module, a 100 mHz analog to digital converter (ADC) with automated energy calibration, and a Si(Li) solid state detector with 150 eV resolution (FWHM) at 5. …