02a0019459;20011205d1996 ekmy0engy01;eng;a z 000yy;r;40Ar/39Ar ages of some Challis Volcanic Group rocks and the initiation of Tertiary sedimentary basins in southwestern Montana;John W. M'Gonigle & G. Brent Dalrymple;Washington;U.S. GPO;1996;iii, 17 p.;1 map;Bulletin;U.S. Geological Survey;no.2132;2001b;aBulletin ; fU.S. Geological Survey ; vno.2132;蒙大拿州西南部第三纪沉积盆地查利斯火山群部分岩层的氩40/氩39年龄与起源;a360 ; a275;M'Gonigle ; Dalrymple;John W. ; G. Brent;101;457301;P;254.2;B87;v2132 ; r1050.00;a03;b1;cP