Analysis of a Middle Archaic Obsidian Cache From
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LITHICS IN THE WEST CHAPTER 10 ongoing at the site and, to date, 62 obsidian artifacts have been recovered. Obsidian is the only lithic raw FROM CLIFF TO CACHE: ANALYSIS OF A material present at the site, and the lack of debitage MIDDLE ARCHAIC OBSIDIAN CACHE indicates that the artifacts were produced elsewhere and FROM SOUTHWESTERN MONTANA cached at the site. Dating by obsidian hydration (OH) and optically stimulated luminescence (OSL) indicates that the Yearling Spring Cache was created during the Middle Archaic Period, approximately 3,700 years ago. A number of the artifacts were found covered in ochre, and a large By Scott L. Carpenter and Philip R. Fisher ochre‐ stained pit was identified eroding out of a cut bank believed to be the cache area. At the bottom of this pit a single flake tool was recovered in situ during ABSTRACT excavation. The other specimens were found down slope The Yearling Spring site (24PA1377) consists of a cache of from this pit either on the ground surface or within the ochre‐covered bifaces, flake tools, and core fragments all existing sod layer (Figure 10.2). We believe that all of made of obsidian. This site was found eroding from a these artifacts likely had been recently eroded out of the cutbank south of the Yellowstone River in southwestern pit and some were subsequently covered by slopewash Montana. Sixty‐one of the 62 pieces were found on the sediments. ground surface or within the sod layer down slope from a Cache sites are relatively uncommon and can occur as recent bank washout. Archaeological excavations isolated sites or as part of a larger site with one or more undertaken during the spring of 2011 revealed a portion functions. Most lithic caches in western North America of a subsurface ochre‐stained pit with one obsidian biface appear to be isolated from other sites and are often in situ. No other artifacts or features were found in discovered only after some or all of the material has association with this subsurface pit. No flake debitage eroded or been accidentally excavated from their was found, indicating that the pieces were not primary context (Rennie and Rittel 2007). Lithic caches manufactured on site. Two specimens with possible use have been discovered in North America throughout the wear were analyzed for protein residue, and were found Archaic period (Rennie and Rittel 2007),and the earliest to exhibit sera for Salmonidae and Cervidae. An ochre known caches are associated with Clovis technology sample tested positive for Ursus sera. Obsidian (Collins 1999; Gramly 1993; Kilby 2008; Kohntopp 2010; specimens were submitted for x‐ray fluorescence Lassen 2005; Wilke et al. 1991). In the region surrounding sourcing, and are attributed to Obsidian Cliff, Wyoming. the Yearling Spring Cache site there are a number of Hydration rim measurements dating to approximately known biface caches. These caches, located in 3680 years B.P., indicate a probable single event of southwestern Montana and Idaho, vary in the stage of procurement and caching. Geoarchaeological studies reduction of the bifaces and in age of the site. The oldest have been undertaken, with optically stimulated and closest cache to Yearling Spring is the Anzick site luminescence dating supporting the obsidian hydration (Lahren and Bonnichsen 1974; Owsley and Hunt 2001; date. Wilke et al. 1991) which is located about 38 km to the north of Yearling Spring. Others in the region include the INTRODUCTION Yellowstone Bank Cache, Montana (MacDonald et al. The Yearling Spring Cache site (24PA1377) is located 2010), the Fenn Cache, from an undisclosed location in in southwestern Montana near the present day town of either Utah, Idaho, or Wyoming (Kornfeld et al. 2010; Livingston (Figure 10.1). The site lies near a small spring a Frison and Bradley 1999) and in Idaho the Simon Clovis few miles uphill from the Yellowstone River. Research is Cache (Kohntopp 2010), the China Creek Cache - 173- LITHICS IN THE WEST Figure 10.1. Map showing general location of Yearling Spring Cache Site in southwest Montana and location of Obsidian Cliff obsidian source in Yellowstone National Park, Wyoming. (Kohntopp 2001), the Cedar Draw Cache (Kohntopp assemblage content, time period, and context, thus they 2006) and others (Pavesic 1966, Plew and Woods 1986). must be approached carefully when trying to determine Caching is a behavior in which an individual or group why a cache was created (Kilby 2008; Lassen 2005). One of individuals hides or conceals a resource for possible explanation proposes that caches form a safety net of retrieval at a later date (Garfinkel et al. 2004; Lassen sorts where a collection of tools are stored that can be 2005). The definition of prehistoric caches often refers to recovered for later use. Caches can therefore be viewed lithic materials, but caches can also include other items. as utilitarian in nature and function as a place of storage The cached material presumably held some value to the for a variety of later uses (Garfinkel et al. 2004, Kilby cacher (Rennie and Retter 2007) due to the fact that if 2008; Lassen 2005; Rennie and Rittel 2007). Another the artifacts are in early stages of production and or use hypothesis is that caches are the result of ceremony or and they have the potential to be used in a great deal of ritual. Ritual caches are often associated with human future activity (Odess and Rasic 2007). Tools in early burials such as the Anzick site in Montana (Kilby 2008; stages of production and use are not at a point in their Lassen 2005; Wilke et al. 1991). However, ritualistic use‐life that warrants abandonment and would not be caches need not be associated with human remains. expected to have been intentionally discarded (Odess Ritual caches can be dedications to ancestors or deities and Rasic 2007). Caching is therefore an intentional act as well as towards future endeavors (Kilby 2008; Lassen by those who cached the material. 2005; Kohntopp 2001). Caches must be assessed A number of hypotheses have been proposed to individually when seeking to determine their possible explain caching behavior. However, caches vary greatly in - 174- LITHICS IN THE WEST Figure 10.2. Topographic map of Yearling Spring Cache site area showing locations of obsidian pieces and ochre stain that eroded out of collapsed cutbank during the spring of 2010. function, such as utilitarian or ritualistic or a combination oxide (Fe2O3), commonly known as red ochre, is an of both (Kilby 2008; Lassen 2005). impure variety of hematite (Erlandson et al. 1999; The use of ochre is often associated with prehistoric Mrzlack 2003; Tankersley et al. 1995). Hematite can be caching in North America (Binford 1972; Kilby 2008; found occurring naturally in geological formations Kohntopp 2010; Lassen 2005; Wilke et al. 1991). Ochre (Erlandson et al. 1999). Prehistoric use of ochre is not has been used for pigment, medicines, and ceremonial limited to caches and is often associated with utilitarian, purposes throughout the world for over 100,000 years medicinal, ritualistic, and ceremonial activities. A few (Henshilwood et al. 2011; Popelka‐Filcoff 2006). Iron important uses of ochre include the tanning of hides, as a - 175- LITHICS IN THE WEST pigment in rock art, decorative application to peoples’ adjacent streams originate to the south on Elephant skin, for medicinal purposes, and use in ceremonial Head Mountain at 2875 m (9431 ft.). contexts associated with burials (Erlandson et al. 1999; Rock lithologies in the headwaters are amphibolite Mrzlack 2003; Tankersley et al. 1995; Wilke et al. 1991). and gneiss, transitioning downstream (northward) into Prior to archaeological excavation at the Yearling the drainage midsection to steeply dipping Cambrian Spring Cache site, an ochre stain was observed in the through Cretaceous sedimentary rocks including exposed cut bank profile. Many of the obsidian artifacts sandstone, limestone, dolomite, quartzite, and shale that were recovered nearby on the surface and from the (Eckerle 2011; Berg et al. 2000). Glacial moraine deposits sod layer were also covered in ochre and/or a mud/ochre also occur in the headwaters and midsection of Mission stain. The staining could be a result either of direct Creek that is situated nearby. The drainages in the application of ochre to the artifacts before caching, of vicinity of the site flow across a piedmont slope which being placed in an ochre–filled pit, or as a result of consists of a composite set of gravel‐capped, pro‐glacial, secondary deposition in a mud/ochre mixture after slope outwash fans which transition to terrace treads near the failure exposed the cache. It appears that the ochre and axis of the Yellowstone River. The upstream origin of the the cache of obsidian artifacts are associated with one fans begins near the confluence of Beaver Creek at another, given that one flake tool was discovered in situ around 1463 m (4800 ft.) and the fans extend to the at the base of what appears to be the edge of the ochre‐ south margin of the Yellowstone Valley where their filled subsurface pit. Based on X‐ray fluorescence gradient flattens to a gravel terrace tread before they spectrometry and obsidian hydration dating, it appears terminate at a scarp‐edge at an elevation of ~1402 m that the site is the result of a single caching event. The (~4600 ft.). These terraces are mapped as “Alluvium of lack of debitage at the site suggests that the artifacts fourth youngest alluvial terrace” and “Alluvium of fifth were produced off site. Currently the Yearling Spring youngest alluvial terrace, oldest” (Berg et al. 2000, map Cache site does not appear to be part of a larger site. legend).