Locality map for scintillometer and analytical data collected in 1981, Ugashik and Karluk quadrangles, Alaska

Abstract

Scintillometer data were collected routinely in 1981 as part of the field investigations in the Ugashik and Karluk quadrangles. The instrument used was a Geometrics Model GR-101A, mounted in the helicopter. The data, in counts per second (cps), were obtained at most of the sites by the helicopter pilot (Svec) while geologists were occupying the sample site. Scintillometer localities are indicated on the map by a dot. The sites are concentrated in the southeastern part of the map area where previous work (OF 81-253) had outlined an area with anomalously high cps. The bedrock at these sites is a Late Tertiary hornblende granodiorite instrusive dated at 9.4 my. Hornfelsed sedimentary rock overlying the batholith gave cps nearly as high as the intrusive rock. Samples routinely checked by semiquantitative spectrographic analysis for thorium failed to detect the element. In general the Ugashik and Karluk quadrangles have a low level of gamma radiation. A majority of the sites, 52 percent, gave readings of less than 35 cps, and only 10 percent had values of greater than cps. Thick alluvium or glacial deposits generally gave low values. Readings from sedimentary bedrock were extremely erratic and no generalization can be made concerning their level of gamma radiation. The hornblende granodiorite and overlying hornfelsed sedimentary rock are all greater than 30 cps, but again, the values are somewhat erratic and no definitive pattern is readily apparent. Bedrock samples are collected for analysis are on the map by a triangle.