pip. No!' 2^3T' McNARY RESERVOIR — SHINER 173 



yielded no information. In 1951, Dr. Harold Culver, of the Depart- 

 ment of Geology at the State College of Washington, examined the 

 deposits at Hat Creek and other exposures in the vicinity. He 

 concurred in the opinion that all of the exposures were homologous, 

 and that the source lay in the Cascade Mountains about 100 miles 

 to the west. The volcanic source could not have been much 

 closer than 100 miles, for the ash itself is composed entirely of minute 

 particles. Were the source closer, the ash would have contained larger 

 particles including pumice. The fact that the ash was airborne over a 

 considerable distance was verified by Dr. Culver. 



Dr. Culver found no basis on which the precise time of the ash fall 

 could be determined. He postulated a postglacial age and late rather 

 than early postglacial. Examination of the ash itself was made by 

 Dr. C. D. Campbell, also of the State College of Washington. He de- 

 scribed the material as very fine volcanic dust with an index refraction 

 of 1.53, indicating andesitic rather than rhyolitic affinities. Part of the 

 material proved to be 90 percent glass with no incipient crystalliza- 

 tion. Another part of the column showed 50 percent crystalline ma- 

 terial, in part plagioclase feldspar. 



Estimates, all admittedly guesses, would place the time of the ash 

 deposition at between 2,000 and 5,000 years ago. Without going into 

 detail, it is the writer's opinion that it would be difficult, indeed, from 

 a cultural perspective, to account for as much as 5,000 years since 

 the eruption. On the other hand, the changes in material culture and 

 depth of deposit seem to require no small amount of time. It is 

 dangerous perhaps to speculate with so little evidence, but the cul- 

 tural data would tend to support a figure closer to 2,000 rather than 

 5,000. 



Recognition of the layer of volcanic dust as a single event permits 

 the relative placement of several of the McNary sites in time. Sites 

 35-UM-3 and 35-UM-5 (Hat Creek) are stratigraphically earlier than 

 the deposition; sites 35-UM-7 (Cold Springs), 35-UM-8, and 

 45-BN-6 are later, since the ash stratum underlies the occupational 

 remains. 



35-UM-5 (HAT CREEK) 



On the south banli of the Columbia about 6 miles east of McNary 

 Dam, Hat Creek empties into the river. The creek is named for Hat 

 Rock, a tall erosional remnant of colunmar basalt that looks like an 

 old beaver hat. This landmark was seen by Lewis and Clark and 

 noted on their map by the name "Hat Rock." 



The site is located on both sides of Hat Creek, a little distance from 

 the river proper. The principal exposure, on the east bank of the 

 creek, was 50 yards from the river ; the one on the west bank was 100 



