“…Dip magnitudes decrease from 7,770 to 7,774 ft from 45°NE to 42°NNE in a tight group of three; next reading is @ 7,790 ft: 23°N, followed by 13°NE @ 7,792 and 18°N @ 7,796 and 7,798 ft. (table 1), are based primarily on my interpretation of the borehole compensated sonic and gamma ray (BHC/GR) log, in conjunction with the compensated neutron-formation density (FDC/CNL) log and log of lithology of returned drill cuttings, commonly known as a mudlog. These data were then compared with those of other drillholes from southwest Montana (Perry and others, 1981;Perry, 1986) as well as descriptions of stratigraphic units by Lowell (1949Lowell ( , 1963, Pecora (1981), and Hildreth (1981). I calculated formation thickness from drilled intervals, picked on the BHC/GR log, on the basis of publicly released dipmeter arrow plots (dip azimuth vs. dip magnitude) for the drill-hole interval 1,002 to 7,918 ft.…”