UC Merced Journal of California and Great Basin Anthropology Title Invaders from the South? Archaeological Discontinuities in the Northwestern Great Basin Permalink https://escholarship.org/uc/item/4gj347dt Journal Journal of California and Great Basin Anthropology, 7(2) ISSN 0191-3557 Author Layton, Thomas N Publication Date 1985-07-01 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Journal of California and Great Basin Anthropology Vol. 7, No. 2, pp. 183 -201 (1985) Invaders from the South? Archaeological Discontinuities in the Northwestern Great Basin THOMAS N. LAYTON N 1972 this author published a series of gist (Cowles 1960), lacks precise provenience Ihydration measurements on obsidian pro­ documentation. jectile points recovered during an archaeologi­ More recently, major excavations were cal excavation at Hanging Rock Shelter conducted under the direction of the author (NV-WA-1502) in northwestern Nevada (Lay- at Last Supper Cave (NV-HU-102), located 32 ton 1972a). These data were used to tempor­ km. northeast of Hanging Rock Shelter. As a ally order a number of recognized Great Basin consequence of these investigations, a point types in the collection. In addition, the 9,000-year obsidian hydration sequence is hydration results indicated possibly two epi­ now available for the site. Among the objec­ sodes of occupational hiatus at the shelter. tives of this paper is a comparative evaluation The earlier break was believed to have coin­ of the hydration records from Hanging Rock cided with the onset of Altithermal climatic Shelter and Last Supper Cave. Given advances conditions (cL Antevs 1953), while the later since 1972 in the measurement of obsidian hiatus was thought to have occurred relatively hydration bands, additional hydration meas­ late during the ensuing Medithermal climatic urements have been obtained for certain of period. At the time of the hydration analysis, the specimens from Hanging Rock Shelter. however, obsidian studies were largely in their Hydration data from both sites collectively infancy and the importance of geochemical support the recognition of terminal and environmental variables had yet to be Anathermal/early Altithermal and late Medi­ fully appreciated by most archaeologists. thermal episodes of occupational hiatus and Moreover, the Hanging Rock Shelter se­ projectile point stylistic discontinuity in quence, spanning some 9,000 years, stood northwestern Nevada. alone as the longest and most well- documented, site-specific obsidian hydration THE SITES record in the general region. The only extant Hanging Rock Shelter and Last Supper record of comparable length consisted of Cave are situated in the heart of the High hydration measurements on obsidian artifacts Rock Country of northwestern Nevada (Fig. from Cougar Mountain Cave (Layton 1972b), 1). A tableland of vast, layered lava beds but this uncataloged assemblage, excavated averaging 1,850 m. above sea level in elev­ and reported upon by an amateur archaeolo- ation, the region is the most southerly exten­ sion of the Columbia Lava Plateau. Lava beds are warped, faulted, eroded, and often ex­ Thomas N. Layton, Dept. of Anthropology, San Jose State posed as rimrock in canyon walls. Vegetation Univ., San Jose, CA 95192. throughout the region can be generally de- [183: 184 JOURNAL OF CALIFORNIA AND GREAT BASIN ANTHROPOLOGY few perishable artifacts were found — primar­ • Cougar Mountain Cave ily near the surface of the deposit. Human occupation of the shelter spans the last 9,000 OREGON IDAHO years, terminating with an historic component (Layton 1973a). Three hundred seventy-eight typable projectile points, almost all of obsid­ • Last Supper Cave « Hanging Rock Shelter ian, were recovered from Hanging Rock Shel­ • Silent Snake Springs Danger Cavei ter. Last Supper Cave was discovered, map­ Soulh Fork Shelter ped, and tested during the summer of 1968 and completely excavated during the summers Honey Lake of 1973 and 1974. Initially exposed by the umboldt Lake Bed 5. downcutting of Hell Creek through a faulted Wagon Jack Shelter* Reese River Valley rhyoHtic lava flow, the cave apparently owes • Alta Toquima Village its origin to the collapse and stream-removal of soft sediments underlying the flow. Situ­ ated at an elevation of 1,650 m., the cave is o approximately 10 m. wide at the mouth and Crooked Fork Site ca. 22 m. deep, with its walls converging CALIFORNIA Owens Valley towards the rear. The cave opens to the east, but its interior is nearly always shaded. Fig. 1. Locations of Hanging Rock Shelter and Last Spring-fed Hell Creek, which flows only mar­ Supper Cave, and other sites mentioned in ginally in late summer, lies 20 m. below the text. floor of the cave. The stratified cultural scribed as Artemisia-domina.tQd Upper Sonor- deposits reach a maximum depth of 1.3 m., an Life Zone. with the lowermost deposits seasonally wet Hanging Rock Shelter was discovered in from groundwater. Numerous perishable arti­ 1967 and excavated during the summer of facts were found in the upper deposits and in 1968 (Layton 1970, 1972a). Lying 53 km. nearby pack-rat nests. A series of radiocarbon south of the Nevada-Oregon border and 45 dates indicate human occupation of the cave km. east of the Nevada-California border, the over the last 9,000 years with, as at Hanging site is located in a canyon formed by the Rock Shelter, a terminal historic component downcutting of Hanging Rock Creek through (Layton 1977a). Approximately 600 typable a massive rhyolitic lava flow. Stream under­ projectile points, again nearly all obsidian, cutting led to the formation of the shelter were recovered from Last Supper Cave. itself. The ground surface of the shelter is approximately 1,700 m. above sea level, and OBSIDIAN AND THE 4.5 m. above Hanging Rock Creek (at present, HIGH ROCK COUNTRY a perennial spring-fed stream). Given its Research in the past three decades has southern exposure, the floor of the shelter shown that the hydration of obsidian is receives some direct sunshine. The cultural controlled by at least three major variables: deposits have a maximum depth of one meter time, temperature, and chemical composition and are seasonally wet from groundwater. (cf. Friedman and Smith 1960; Friedman and Consequently, during the excavation only a Long 1976; Taylor 1976; Michels and Tsong INVADERS FROM THE SOUTH? 185 1980). In most cases, the specific temperature ature history than do obsidian artifacts found history of an obsidian tool over thousands of at open sites where hydration may proceed at years is extremely difficult to ascertain. Vag­ accelerated rates because of higher effective aries of preservation, including duration of temperatures (Layton 1973b). ground-surface exposure, depth of burial, and climatic changes, all contribute to a highly THE DATA variable temperature history. Likewise, the The present study is based on hydration chemical composition of a particular obsidian measurements for 126 obsidian projectile tool and the chemistry of the soil in which it points from Hanging Rock Shelter and 121 lies directly influence the rate of hydration in obsidian points from Last Supper Cave. Both ways not yet fully understood. The absence samples include most of the major point types of adequate controls over both the tempera­ known for the northern Great Basin. With the ture history and chemical composition of exception of Great Basin Stemmed series archaeological obsidian in many published points (Layton 1979: 47; Tuohy and Layton hydration studies has often led to anomalous 1977), the type designations used here follow results which, in turn, have forced extremely the morphological key proposed by Thomas cautious applications of this dating method. (1981a) for the central and western Great Fortuitously, the High Rock Country of Basin. northwestern Nevada is a region ideally suited Hydration values for the specimens from for obsidian hydration dating since, for a Hanging Rock Shelter were obtained by Paul number of reasons, some degree of control Aiello at the University of California, Los can be achieved over the temperature histories Angeles, Obsidian Hydration Laboratory in and chemical compositions of obsidian arti­ 1970. Hydration on the Last Supper Cave facts. First, obsidian occurs in abundance specimens was measured in 1979 by Marvis throughout the High Rock Country. Thus, Kelly, under the supervision of R. E. Taylor, local obsidian has been the primary tool at the University of Cahfornia, Riverside, material throughout prehistoric human occu­ Obsidian Hydration Dating Laboratory. Origi­ pancy of the region (over 95% of all exca­ nally, in an attempt to at least minimally vated chipped-stone tools are made of obsid­ control for geochemical variability, artifacts ian). Second, obsidian trace-element charac­ from both sites were candled and only those terization studies in northwestern Nevada are displaying a similar color and degree of fairly advanced due to the efforts of Jack translucency were selected for measurement. (1976), Erickson, Hagan, and Chesterman Subsequently, however, at the suggestion of (1976), and Hughes (1983a, 1983b, 1985). Taylor (personal communication 1979), two Finally, numerous exogene rockshelters occur apparent problems in the extant hydration throughout the High Rock Country exposed data were addressed with additional, focused at the basal edges of dissected lava flows. laboratory analysis. First, Taylor observed Many of these shelters contain multicom- that in both sample