A NEW LOOK AT MONO BASIN OBSIDIANS Richard E. Hughes tIN,.ODUCTION Over the past decade, archaeologists in the Far West have made tremendous strides toward understand- ing the prehistoric uses of obsidian. This understand- ing, however, did not derive solely from within archaeology, but is best understood as a highly benefi- cial consequence of a partnership forged between archaeology and the physical sciences- in particular geology, chemistry and physics. Geochemical studies of obsidian have provided the data base from which inferences about the existence of long distance convey- ance networks and differences in source use by artifact function have been advanced. Such studies have received well deserved notoriety, and I believe that several of these avenues of research have taught us things about the past that we could not have learned any other way. However laudable, many of these descriptive and interpretive papers prepared by archaeologists have relied on older geochemical studies that have been superceded by current work. For example, some of the atifact-to-source attributions made in Jack's (1976) pioneering study of prehistoric California obsidian use were in error- partly because the source inventory for certain parts of the state was much less complete than it is today, and partly because the artifact analyses in those days were not reported quantitatively in interna- tional measurement units (i.e. in parts per million [ppm] and weight percent composition). Aside from the issue of interlaboratory comparison, it is now widely recog- nized that quantitative data are indispensable for distinguishing among certain varieties of chemically similar obsidians, and that quantitative data are some- times the only way researchers can identify and separate glasses from different geographic sources that have superficially similar geochemical "profiles". While these facts are well known to the few specialists currently involved in archaeometric studies of volcanic glasses, such information has not filtered to the large number of archaeologists who routinely use older data for interpretive purposes. Consequently, the results of older work becomes conventionalized in the archaeo- logical literature, and it is only rarely that older results are subjected to critical scrutiny or re-evaluation. Although it has been argued that archaeologists should be concerned with developing research strategies to address what we don't know (Binford 1986), I have suggested that it is equally important to critically evaluate assumptions that may never have been subjected to serious scrutiny but that, through repeti- tion, have become embedded as conventional knowl- edge (Hughes 1988a). It is only by engaging in such critical exercises that incorrect conventions can be exposed and replaced by results obtained through more exacting methods. Contributions of the Archaeological Research Facility Number 48, December 1989 For the past year or so, I have been involved in field and laboratory studies of the geochemistry of obsidians from the Coso volcanic field and, more recently, obsidians from the Mono Basin (see Figure 1). At first blush, there would appear to be little reason for spending one's time studying either of these two places since the trace element geochemistry of Coso obsidian and Mono Basin obsidians has been in print for more than a decade (Jack and Carmichael 1969; Jack 1976). However, my choice of these research sites was guided by a concern for reexamination of convention; specifi- cally, those conventions derived from early trace element work that have come to influence the way archaeologists use the terns "Coso" and "Mono Basin" obsidians. My Coso research (Hughes 1988a) showed that orthodox views about this "source" were in error; specifically, four geochemically distinct obsidians suitable for toolstone manufacture were exploited pre- historically in the Coso volcanic field and environs- not the single "Coso" variety assumed by previous workers. In addition, major and minor element chemical data indicated that each of these glass types should hydrate at a slightly different rate (Hughes 1988a; see Steven- son and Scheetz [this volume], and Ericson [this vol- ume]). In light of the Coso results, it seemed appropri- ate to extend the re-examination of convention to the Mono Basin; specifically, the Mono Craters and Mono Glass Mountain obsidian sources of central eastern California. BACKGROUND In California, no study of geochemical characteri- zation of obsidian use can proceed without reference to the pioneering work of Robert Jack (1976; Jack and Carmichael 1969). In the first significant pilot study of California obsidians, Jack and Carmichael (1969) employed wavelength dispersive x-ray fluorescence analysis to identify unique trace element signatures for nearly all the volcanic glasses they examined except for . two groups of samples which are virtually indistinguishable from one another; these are the extrusive materials of Mono Craters and those of (Mono) Glass Mountain 20 or so miles toward the east in the Mono basin" (Jack and Carmichael 1969: 22). Their conclusion was that "no really definite trace- element criteria can be found to distinguish the acid lavas from the two (Mono Craters/Mono Glass Moun- tain) centers" (ibid.; my addition). In a later study employing larger numbers of powdered geological obsidian samples from Mono Craters and Mono Glass Mountain, Jack (1976: 191, 203) was able to recognize geochemical distinctions between these sources. However, the non-quantitative, rapid-scan (i.e., semi-quantitative) technique he employed to study artifacts was unsuccessful in replicating the distinctions generated from quantitative analyses of powdered obsidian source samples. In short, the quantitative data (generated from analyses of crushed and powdered obsidian samples) provided a separation between these two sources, but the semi- quantitative (i.e., peak ratios generated from unmodi- fied artifacts) data could not. Through subsequent experimentation, Jack found that Fe Ka / Mn KB intensity ratios (semi-quantitative data) effectively separated geological obsidian samples from the two sources, so this non-destructive technique was applied to archaeological specimens (see Jack 1976: 212). Despite Jack's apparent success in drawing meaningful distinctions between these two sources using non- destructive Fe/Mn ratios, Jackson (1974: 13-14, 77)- using the same x-ray fluorescence system and analytical conditions- found that this ratio did not unambiguously separate Mono Craters from Mono Glass Mountain obsidian at archaeological sites around June Lake. To put this in perspective, it is important to remember that this x-ray work was conducted more than 15 years ago, well before the advent of energy dispersive x-ray fluorescence spectrometers employing microcomputer-based software capable of generating quantitative estimates of certain minor, trace, and rare earth elements non-destructively. The point here is that since no substantive archaeometric research has been undertaken on the problem since 1974, it is understand- able that archaeologists repeat the convention that "Mono Craters obsidian is often chemically indistin- guishable from Mono Glass Mountain" (cf. T. Jackson 1974: 50 with R. Jackson 1985: 106; Hull 1988: 172). THE PROBLEM From the present standpoint, the question was whether or not it was possible to identify quantitatively significant contrasts- using current state-of-the-art instrumentation- that would separate Mono Craters from Mono Glass Mountain obsidians nondestruc- tively. While Jack had demonstrated that these glass types could be separated geochemically, his results applied strictly to crushed and powdered samples (i.e., the contrasts were identified using a destructive form of analysis). Thus, despite the demonstrated ability to partition Mono Craters from Mono Glass Mountain glasses, Jack's results are of limited archaeological 2 A New Look at Mono Basin Obsidians 3 FIGURE 1 LOCATION OF THE STUDY AREA IN CENTRAL EASTERN CALIFORNIA (INSET), SHOWING OBSIDIAN COLLECTION AREAS A I o .\ () G.. I A K E' RJ Panum Crater Grtanite luiti . .. _ , . . . ;. :. .! ' 8 ': ... ..... .. . . . .. 8.-- ,', ;,- ,- ,'. 'w':' ," ;' ..,, ,-, '. :,, .'. ,' .. . . * * X *- . .* - ' . :'i .-\lono CXraters . ... .: ;. :. - * .; ,. ...:. . . : .. .. . ; ES1t .... .. ;.; .. .... ..... ..,., X . ,,.,D,.......... R40r .. .; .. . i :. t--.' Bald Nlountainz-^,,, 1, 0 ,\ I nyo Craters 0 5 Miles I Contributions of the Archaeological Research Facility Number 48, December 1989 utility because the contrasts were determined using a technique which required sacrificing some portion of the specimen for analysis. The present study has an explicit bias toward identifying elemental contrasts that can be applied to archaeological specimens without sacrificing ajY portion of an irreplaceable archaeologi- cal artifact (see also Hughes 1986, 1988b). The ques- tion, then, is whether artifacts manufactured from Mono Craters obsidian are distinguishable geochemically from specimens fashioned from Mono Glass Mountain material. To address this issue, it was first necessary to collect and analyze geological samples from several areas at both sources. Obviously, if geochemical distinctions could not be recognized between source specimens, it would be pointless to extend the study to an analysis of artifacts. The principal bias attending sample collection was that the obsidian had to be of toolstone caliber; loci containing obsidians charged with abundant phenocrysts and spherulites were not included in this study. The presence of prehistoric knapping stations associated with several of the collection locations made it readily apparent that they contained obsidian suitable for analysis. THE STUDY AREA Mono Craters and Mono Glass Mountain (see Figure 1) have attracted the attention of geologists for more than a century, beginning with I.C. Russell's (1889) pioneering work in the Mono Valley area. Glass Mountain erupted silicic rhyolite (obsidian) sporadi- cally during between ca. 2.1-1.2 million years ago (m.y.a.) and 1.1-0.8 m.y.a. (Metz and Mahood 1985). Mono Craters glasses are much younger- the earliest are Holocene in age, but some researchers believe that aphyric glasses erupted rather late in the sequence, perhaps within the past 2,000 years (Friedman 1968; Wood 1984). Obsidian at Mono Craters was erupted as recently as ca. 600 years ago, about the same time as obsidian at Inyo Craters ca. 20 kan to the south (Sampson 1987; Sampson and Cameron 1987). Inter- ested researchers should consult the recent geological literature (e.g., Gilbert et al. 1968; Loney 1968; Noble et al. 1972; Bailey, Dalrymple, and Lanphere 1976; Wood 1977; Hildreth 1979; Miller 1985; Metz and Mahood 1985; Sieh and Bursik 1986; Sampson and Cameron 1987) on the Mono Craters, Mono Glass Mountain and the Inyo volcanic chain for detailed discussion of the complex eruptive history in the Mono Lake/Long Valley area an environs. ANALYSIS AND RESULTS: GEOLOGIC SOURCE SPECIMENS Samples analyzed in the present study were collected at nine different loci at Mono Craters and Mono Glass Mountain (see Figure 1), and each group of specimens was subjected to x-ray fluorescence analysis to determine quantitative composition of ten minor, trace, and rare earth elements (see Table 1). All of these measurements were determined non-destructively on unmodified flakes and chunks with suitably flat surfaces. The analytical technique and calibration procedure employed for the x-ray analyses have been described elsewhere (Hughes 1988a). Although quantitative values for the element barium (Ba) have proved extremely useful for distinguishing between some chemically similar obsidians (e.g. Bodie Hills vs. Pine Grove Hills [see Hughes 1985], and Franz Valley vs. Napa Valley [see Jackson, this volume]), Ba occurs in both Mono Craters and Mono Glass Mountain obsidians in concentrations below the detection limit (< 14 ppm) of the x-ray fluorescence instrument employed here (see Hughes 1988a). Consequently, Ba concenta- tions were not measured for either Mono Craters nor Mono Glass Mountain source standards. Table 1 presents the selected minor and trace element measurements determined for obsidian samples from each sampling locus. Initially, each locus from each source was treated as a separate unit. However, a one-way analysis of variance (ANOVA) test performed on the six best measured elements from Mono Craters and Mono Glass Mountain showed no significant departure from randomness at the 0.05 alpha level. The sole exception was the element rubidium (Rb) with shows relative depletion in Mono Glass Mountain sampling loci R5 and R6 (see Table 1). Noble and Hedge (1970) observed a similar situation with Rb in their Mono Glass Mountain samples, attributing the observed differences to "small variations in the degree of late-stage crystal fractionation" [in the parent magma] (Noble et al. 1972:1180; my addition). This finding of intra-source homogeniety is congruent with the results of other researchers (e.g. Loney 1968; Jack and Carmichael 1969:19), and the elemental data generated here are in excellent agreement with those published by previous analysts (see Table 2). Figure 2 illustrates the agreement between the non-destructive, quantitative measurements generated herein with the previous x-ray fluorescence work of Jack. Samples OS-9 and OS-10 represent, respectively, powdered obsidian samples from Mono Craters and Mono Glass Mountain (cf. Table 2). 4 A New Look at Mono Basin Obsidians O -4 t...-- 00 v c C4 11 -tv crsv 9I ~ . "' I q 4 C _: 1 0 i a 00 0 00 0 -Cl 'n ooo m t- 00 I*t c C vn - -4 riO ..0 %O A % 0 00 C4t F( o: 11 -W t . _ . v) tn V % 0 N r en e4 -4 C_ - N O V .' . 0-11 . 0% C II4 In (: 1 C l - r i o v c .4 . 9 ci 9 6 6 04 ei U2 rA vi 9 4.0 C: 4) 1- E 6 w P A SE (4 a"O " 4 rb u _ sa 0 r _?40 VI .8g G = 8 > 0 *2 o 3.a tn~~~~~~ ~ ~ ~ ~ O 00 t-VV% ne C 0 ItNq n N0 1: -4 V 04 *0o YIu 0 , - 00 _o qt f- _ ,-t N tn n cn C4 > 5 _ _ , . 8 boob '0 v %n ao fi v Fo t- t- fi - t - Cl e a ^ O VI~~~~~~~~~~~- p4 :1I 0EI0 *F ^ 0 m aQ0 5 0-1 iWII 1 r. _-1 _tv' c, 0 0 z 0 2 R uz 0 z 0 U En 0 z 0 04 0 z F- 04 0 U -J U F- 0 z iz co 0 E- E- 0 C4 I- U U z ow U z z F - ut r) z 0 C., 0 0.- V-J F- ClRrS H, ' Contributons of the Archaeological Research Facility Number 48, December 1989 FIGURE 2 SCATTER DIAGRAM OF ZR VS. MN COMPOSITION FOR GEOLOGIC SOURCE SPECIMENS FROM MONO GLASS MOUNTAIN AND MONO CRATERS, WITH 95% CONFIDENCE INTERVAL ELLIPSE OVERLAYS 120- 100- 80- 60- Mono Craters Mono Glass Mountain JACK (Os-10) 325 350 I 1 375 400 Mn (ppm) 425 450 Glass Mountain A R5 A RG * ES-Al A ES-A2 A ES-A3 A RJ Mono Craters m RI o R2 o R3 * R4 a RJ Different symbols represent values for obsidians collected from locations secifiled in FiaUe 1. Zr (ppm) 6 A New Look at Mono Basin Obsidians FIGURE 3 HISTOGRAM OF TOTAL IRON (FE203T) COMPOSITION OF MONO GLASS MOUN- TAIN AND MONO CRATERS OBSIDIANS COMPARED TO ARTIFACTS FROM LEE VINING (CA-MNO-446) AND FORT MOUNTAIN ROCKSHELTER (CA-CAL-991) 10- Number of Specimens 5- I Mono Glass Mountain ITI I - I I I - I I I I IT I- ft .80 .90 1.0 11 Fe23T Weight Percent Mono Craters , I . 1 m I . l . I I I I I I I I I 1 1.2 1.3 Open squares to the left of the figure represent Mono Glass Mountain source specimens, while filled squares are values for artifacts L-305 and L-405 from Mno-446. Stippled squares at the rght of the figure represent Mono Craters source specimens, while open squares are values for eight samples from Mno-446 (L-72a, -72b, -93a, -93b, -395, -435, -516b, -530b) and two from Cal-991 (389-138 and -178). The results of the x-ray analyses can be seen in Figure 2, plotting the concentration of Zr against Mn. I selected these two elements because they help draw the clearest contrasts between these two sources. Each symbol represents a group of specimens sampled from loci specified on Figure 1. The ellipses express the 95% confidence limits for Zr and Mn for each source (see Pires-Ferreira [1975] and Hughes [1988a] for discus- sion of probability ellipses). It is clear from this figure that Mono Glass Mountain obsidian contains lower concentrations of both Zr and Mn than Mono Craters, and that Mono Glass Mountain is more variable in Mn composition. Perhaps the sharpest contrast between these sources can be illustrated by comparing their total iron (Fe2031) concentrations (Figure 3). Again, Mono Glass Mountain contains considerably less total iron than Mono Craters. This difference is particularly noteworthy since the iron results are expressed here in weight percent units, not parts per million; thus each increment on this graph (Figure 3) represents 200 ppm. ANALYSIS AND RESULTS: OBSIDIAN ARTIFACTS While the elemental data reviewed above support the position that geologica samples of Mono Craters obsidian can be distinguished non-destructively from those occurring at Mono Glass Mountain, there remains the issue of whether or not these distinctions can be applied productively to archaeological research. To address the archaeological issue, I selected a small group of specimens from two archaeological collec- tions; the Lee Vining site (Mno-446) and Fort Mountain Rockshelter (Cal-99 1). I had previously analyzed specimens from both of these sites (Hughes 1981, 1988c), and was unable to attribute them with confi- dence to either Mono Craters or Mono Glass Mountain using the criteria proposed by Jack (1976). While it would be desirable to reanalyze all of the specimens originally attributed by Jack (1976) to Mono Craters/ I I I I I I - I 7 r- Contributions of the Archaeological Research Facilit Number 48, December 1989 z os " F t 3, ?^ ' g t 8, ol% O 8 0~~~~~~~~ Eu I X V^ e n R ? z o 0 o wS U) >1~~~~~~~~~~~~~~~~~~~~~* 0 0X - I o, I 2 E E ? g o g WI z OhX w w w - > e 8 R a U) ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ V O I o I > Z 0,,)W o 01; - N - - ^ > A]M 8 A New Look at Mono Basin Obsidians Mono Glass Mountain, the present sample from Mno- 446 and Cal-991 illustrates the archaeological utility of these quantitative data. Figure 4 shows the Zr and Mn concentrations for artifacts from Lee Vining (Mno-446) and Fort Moun- tain Rockshelter (Cal-991) in relation to 95% probabil- ity ellipses for each source. Although there is some scatter along the Mn axis for Mono Craters specimens, it is no more extreme statistically than that observed in source samples. Figure 3 illustrates the total iron composition of the Mno-446 and Cal-991 artifacts plotted in relation to Mono Craters and Mono Glass Mountain source standards. DISCUSSION It is worth considering briefly why iron and manganese values were used successfully here to separate Mono Craters and Mono Glass Mountain non- destructively, when previous attempts were largely unsuccessful. Previous workers dealing with geology/ archaeology issues were not able to present quantitative measurements for iron due, in part, to the inherent technological limitations of microcomputerless x-ray spectrometry in the early-late 1970's. Although Mn values generated from analysis of powdered obsidian samples were published (Jack (1976: Tables FIGURE 4 SCATTER DIAGRAM SHOWING 95% CONFIDENCE INTERVAL ELLIPSES FOR ZR AND MN COMPOSITION IN OBSIDIAN SOURCE SPECIMENS FROM MONO GLASS MOUNTAIN AND MONO CRATERS COMPARED WITH VALUES FOR ARTIFACTS (FILLED TRIANGLES) Zr (ppm) A Mono Craters A A& + Mono Glass Mountain 100- A A? A 80- 60- 35 3 40 3 7 Mn (ppm) Zr and Mn values for both artifacts within the Mono Glass Mountain ellipse were generated for specimens L-305 and -405 from Mno-446 (see legend for Figure 3); values for artifacts corresponding with the Mono Craters ellipse are the same ten specified in the legend for Figure 3, above. 400 425 120- 9 325 350 375 450 Contributions of the Archaeological Research Facility Number 48, December 1989 TABLE 3 CHEMICAL INDEX VALUES FOR MONO GLASS MOUNTAIN AND MONO CRATERS OBSIDIAN Source sample number GM-2 GM-4 MO-3B A n obsidian Iame 1 1 1 Obsidian Source (Geochemical Type) Mono Glass Mountain Mono Glass Mountain Mono Craters Mono Craters Determined from data presented in Noble et al. (1972: Table 1). 11.1-11.5; Jack and Carmichael 1969: Table 1), Jack's only use of iron was semi-quantitative (peak intensity counts; see Jack 1976: 188). In the Mono Craters/ Mono Glass Mountain case, the difficulty with employ- ing semi-quantitative data (peak intensity count ratios) is that values for iron and manganese vary in the same direction; Mono Glass Mountain contains less manganese Apj iron than Mono Craters. Consequently, despite differences in absolute concentrations, ratios of these values (Fe and Mn) will be quite similar. I suspect that if iron composition had been reported quantitatively, the prevailing convention that Mono Craters and Mono Glass Mountain cannot be clearly distinguished would never have come into existence. Implications for Obsidian Hydration Studies This study has been concerned specifically with using trace element geochemistry to segregate Mono Craters and Mono Glass Mountain obsidian non- destructively, but it is relevant to discuss some of the implications of these findings for obsidian hydration dating. It is widely known that although variability in trace element composition is the most practical way to "fingerprint" obsidian sources and artifacts, it is the variability in major and certain minor constituents of volcanic glass which appear to directly influence the obsidian hydration process (Friedman and Long 1976). So, while these trace element data show distinctions between sources, they are not directly relevant to determining potential differences in hydration rates. Fortunately, the major and minor element composi- tion for obsidian from Mono Craters and Mono Glass Mountain has been published (Carmichael 1967: Table 5; Noble et al. 1972: Table 1), so it was possible to derive the chemical index values for each glass type (cf. Friedman and Long 1976: 347) to see whether or not significant differences obtained. Table 3 shows that Mono Craters obsidian has chemical index values of 44-46, while Mono Glass Mountain has a value of 53. These differences support the position that Mono Glass Mountain and Mono Craters obsidian should hydrate at slightly different rates- but whether these differences are of sufficient magnitude to effect obsidian hydration dating studies is somewhat more difficult to address with data presently at hand. To illustrate the current difflculty in extrapolating from chemistry to chronometrics, consider current studies in the Coso volcanic field. Stevenson and Scheetz' (this volume) induced hydration research with two varieties of Coso volcanic field obsidian shows an agreement between chemical index values and induced hydration estimates for one source (Sugarloaf Moun- tain), while the induced rate for the other (West Sugarloaf) is slightly slower than that predicted by the chemical index. On the other hand, Ericson's (this volume) induced hydration wotk with the same Mg glassel indicates no significant difference in hydration rates between the two flows. The implications for the Mono Craters/Mono Glass Mountain case are corre- spondingly contradictory; foliowing Ericson's lead, the differences in chemical indexes between Mono Craters Chemical Index 53 53 46 44 10 A New Look at Mono Basin Obsidians and Mono Glass Mountain might well convert to iignificant differences in hydration rate. Alterna- tively, extrapolation from Stevenson and Scheetz' results would support the position ta potendally signficant hydration rate differences may obtain between the two sources. In any event, it is clear that actual induced hydration experiments will have to be conducted on source samples from Mono Craters and Mono Glass Mountain before further speculation is warranted. Outside the laboratory, of course, archaeol- ogically relevant hydration rate calculations must include consideration of a host of affective variables (see Ericson [this volume]) including effective hydra- ion temperature (EHT) extant in particular burial envi- roments, as well as potential changes in these through time. CONCLUDING COMMENTS The results of this study show that non-destructive energy dispersive x-ray fluorescence spectrometry is capable of identifying comparatively fine-grained disinctions between the geochemical compositions of acid lavas from Mono Craters and Mono Glass Moun- tain, and that these distinctions are directly applicable to the study of archaeological collections. These Mono Craters/Mono Glass Mountain results, along with those generated independently in the Coso volcanic field (Hughes 1988a), will hopefully stimulate renewed interest and research on other obsidian "sources" assumed to represent indivisible geochemical types. Such research might prove fruitful elsewhere in the Mono Basin area; specifically, at the Casa Diablo source where rhyolitic flows of different ages have been identified (Bailey 1989) which may have produced obsidians with contrasting trace element geochemis- tries. ACKNOWLEDGMENTS I thank Peter Ainsworth, Rob Jackson, Linda Reynolds, Elizabeth Skinner, and Wallace Woolfenden for help in securing source samples from Mono Craters and Mono Glass Mountain. Joachim Hampel, Depart- ment of Geology and Geophysics University of California, Berkeley, generously provided splits from Robert Jack's Mono Craters and Mono Glass Mountain powdered obsidian samples (OS-9 and OS-10 in Figure 2 and Table 2 herein). I also appreciate the assistance of Robert Jack, who through the years has provided me with copies of his notes and raw data and allowed me to present the results of some of his unpublished obsidian work. Tammara Ekness-Hoyle drafted the graphics that appear herein. REFERENCES CITED Bailey, R.A. 1989. Geologic map of the Long Valley Caldera, Mono-Inyo Craters Volcanic Chain, and Vicinity, Eastern California. US. Geological Survey, Miscellaneous Investigations Series, Map 1-1933. Bailey, R. A., G. B. Dalrymple, and M. A. Lanphere 1976. Volcanism, strucre, and geochronology of Long Valley caldera, Mono County, California. Journal of Geophysical Research 81: 725-744. Binford, L. R. 1986. In pursuit of the future. IN: American Archaeology Past and Future, edited by David J. Meltzer, Don D. Fowler and Jeremy A. Sabloff. Pp. 459-479. Smithsonian Institution Press, Washington, D.C. Carmichael, I. S. E. 1967. The iron-titanium oxides of salic volcanic rocks and their associated ferro- magnesian silicates. Contributions to Mineral- ogy and Petrology 14: 31-64. Ericson, J. E. 1981. Exchange and production systems in Californian prehistory: the results of hydration dating and chemical characterization of obsidian sources. British Archaeological Reports International Series 110. Oxford. Ericson, J. E., T. A. Hagan, and C. W. Chesterman 1976. Prehistoric obsidian in California II: geologic and geographic aspects. IN: Advances in Obsidian Glass Studies: Archaeological and Geochemical Perspectives, edited by RE. Taylor, pp. 218-239. Noyes Press, Park Ridge, New Jersey. Friedman, I. 1968. Hydration rind dates rhyolite flows. Science 159: 878-880. Friedman, I., and W. Long 1976. Hydration rate of obsidian. Science 191: 347-352. Gilbert, C. M., M. N. Christensen, Y. Al-Rawi, and K. R. Lajoie 1968. Structural and volcanic history of Mono Basin, California-Nevada. IN: Studies in Volcanology: A Memoir in Honor of Howel Williams, edited by Robert R. Coates, Richard L. Hay and Charles A. Anderson. Geological Society of America Memoir 116:275-329. Hildreth, W. 1979. The Bishop Tuff: evidence for the origns of compositional zonation in silicic magma chambers. IN: Ash-Flow Tuffs, edited by Charles E. Chapin and Wolfgang E. Elston. Geological Society of America, Special Paper 180: 43-75. Hughes, R. E. 1981. Sources of obsidian at Lee Vining (CA-Mno-446), Mono County, Califoria. IN: Archaeology of the Lee Vining Creek site, FS- 05-05-51-219 (CA-Mno-446), Mono County, Califomia, by Robert L. Bettinger. Manuscript on file, Inyo National Forest, Bishop, CA. 11 Contributons of the Archaeological Research Facilty Number 48, December 1989 1985. Obsidian source use at Hidden Cave. IN: The Archaeology of Hidden Cave, Nevada, by David Hurst Thomas. Anthropological Papers of the American Museum of Natural History 61: 332-353. 1986. Energy dispersive x-ray fluorescence analysis of obsidian from Dog Hill and Burns Butte, Oregon. Northwest Science 60: 73-80. 1988a. The Coso volcanic field reexamined: im- plications for obsidian sourcing and hydration dating research. Geoarchaeology: An Interna- tional Journal 3: 253-265. 1988b. Archaeological significance of geochemi- cal contrasts among southwestern New Mexico obsidians. Texas Journal of Science 40: 297- 307. 1988c. X-ray fluorescence analysis of 15 obsid- ian artifacts from Fort Mountain Rockshelter (CA-Cal-991), Calaveras County, Califomia. IN: Archaeological Investigations at Fort Mountain Rockshelter (CA-Cal-991), a Late Prehistoric Habitation Site in Cental Calaveras County, California, by Greg White. Manuscript on file, Bureau of Land Management, Sacramento, CA. Hull, K. 1988. Obsidian studies in Yosemite National Park preliminary observations. Proceedings of the Society for California Archaeology 1: 169- 187. Jack, R. N. 1976. Prehistoric obsidian in California I: geochemical aspects. IN: Advances in Obsidian Glass Studies: Archaeological and Geochemi- cal Perspectives, edited by RE. Taylor, pp. 183- 217. Noyes Press, Park Ridge, New Jersey. Jack, R. N., and I. S. E. Carmichael 1969. The chemi- cal '"mgerprinting" of acid volcanic rocks. California Division of Mines and Geology Special Report 100: 17-32. San Francisco. Jackson, R. J. 1985. An archaeological survey of the Wet, Antelope, RailMroad, and Ford timber sale compartments in the Inyo National Forest. Manuscript on file, Inyo National Forest, Bishop, CA. Jackson, T. L. 1974. The economics of obsidian in cental California prehistory: applications of x- ray fluoresence spectaphy in archaeology. Unpublished M.A. thesis, Deatment of Anth- pology, San Francisco State University. Loney, R. A. 1968. Flow structure and composition of the south coulee, Mono Craters, Califomia- a pumiceous rhyolite flow. IN: Studies in Vol- canology: A Memoir in Honor of Howel Williams, edited by Robert R. Coates, Richard L. Hay and Charles A. Anderson. Geological Society of Amerka Memoir 116: 415-440. Metz, J. M., and G. A. Mahood 1985. Precursors to the Bishop Tuff eruption: Glass Mountain, Long Valley, California. Journal of Geophysical Research 90 (B13): 11,121-11,126. Miller, C. D. 1985. Chronology of Holocene eruptions at the Inyo volcanic chain, California- implica- tions for possible eruptions in Long Valley caldera. Geology 13: 14-17. Noble, D. C., and C. E. Hedge 1970. Distribution of rubidium between sodic sanadine and natual silicic liquid. Contributions to Mineralogy and Petrology 29: 234-241. Noble, D.; C., M. K. Korringa, C. E. Hedge, and G. 0. Riddle 1972. Highly differentiated subalkaline rhyolite from Glass Mountain, Mono County, Califomnia. Geological Society of America Bulletin 83: 1179-1184. Pires-Ferreira, J. W. 1975. Formative Mesoamerican exchange networks with special reference to the Valley of Oaxaca. Memoirs of the Museum of Anthropology, University of Michigan 7. Russell, L. C. 1889. Quaternary history of Mono Valley, Califomia. Eighth Annual Report of The US. Geological Survey for 1889: 267-394. Sampson, D. E. 1987. Textual heterogeneities and vent area structures in the 600-year-old lavas of the Inyo volcanic chain, eastern Califonia. IN: The Emplacement of Silicic Domes and Lava Flows, edited by Jonathan E. Fink Geological Society of America Special Paper 212: 89-101. Sampson, D. E., and K. L. Cameron 1987. The geochemistry of the Inyo volcanic chain: mul- tiple magma systems in the Long Valley region, eastern Califomia. Journal of Geophysical Research 92 (B10): 10,403-10,421. Sieh, K., and M. Bursik 1986. Most recent eruption of the Mono Craters, eastern cental California. Journal of Geophysical Research 91 (B 12): 12,539-12,571. Wood, S. H. 1977. Distribution, correlation, and radiocarbon dating of late Holocene tephra, Mono and Inyo craters, eastern California. Geological Society of America Bulletin 88: 89- 95. 1984. Obsidian hydration-rind dating of the Mono Crats. IN: Holocene Paleoclimatology and Tephrochronology East and West of the Cental Siefran Crest, edited by Scott Stine, Spencer Wood, Kerry Sieh, and C. Dan Miller. Field Trip Guidebook for the Friends of the Pleistocene, Pacific Cell, October 12-14, 1984. Genny Smith Books, Palo Alto, CA. 12