48 LAKAMIE BASIN, WYOMING. 
of the ridge. The synclinal area of the Casper formation east of 
Boulder Ridge terminates in Colorado a short distance south of the 
state line. On the west side of Boulder Ridge there are gentle 
slopes of granite which dip beneath the Casper formation at low 
angles into the wide syncline extending to Red Mountain. 
In the northeast corner of T. 13 N., R. 74 W., and in the northwest 
corner of T. 13 N., R. 73 W., just southeast of Sportsman Lake, there 
is a small anticline, parallel to the main flexure of Boulder Ridge, 
which is marked by curved ' outcrops of the Forelle limestone. On 
the south side of Hutton Lake the two limbs of the Boulder Ridge 
anticline are shown, the beds on the west side dipping south of west 
at an angle of 15° and those on the north side dipping north of east 
at angles of 50° to 85°. The steeply dipping beds from Morrison to 
Benton outcrop in a prominent ridge along the south side of the lake. 
On the east limb of this anticline there is a small co-shaped flexure 
in the Mowry shales which is clearly exposed on the south shore of 
the lake. On Laramie River the Niobrara dips to the northeast at 
an angle of 5° on the east side of* the Boulder Ridge anticline and at 
about the same angle to the southwest on its opposite side. Benton 
outcrops along the axis of the Boulder Ridge anticline as far north 
as the west end of The Big Hollow. In this hollow the uplift is 
clearly shown in extensive exposures of the Niobrara, which on the 
east side of the flexure has nearly vertical dips. (See sec. 4, PI. VIII.) 
KED MOUNTAIN-JELM MOUNTAIN AREA. 
Jelm and Ring mountains are due to an anticline of irregular form 
crumpling and faulting the beds along the southwestern margin of 
the syncline of Laramie Basin. There are several axes with numer- 
ous variations in pitch but having a general north-south strike. 
To the south, in Red Mountain and in Colorado, they merge into a 
broad area of gentle undulations well exhibited in beds from Casper 
to Cloverly. In the depression east of Red Mountain the strata are 
broken by a fault with downthrow on the east side amounting to 
several hundred feet. It extends from the south, in Colorado, and 
ends a few miles northeast of Red Mountain in an eastward-dipping 
monocline of Chugwater (upper part) and overlying formations. 
North of Red Mountain there is a prominent rise in the anticlines on 
the west bringing up the pre-Cambrian in Ring Mountain and again 
in Jelm Mountain. The anticline on the east shows granite in a 
short ridge just east of Ring Mountain, but the axis then bears to the 
northeast and the anticline pitches downward rapidly. It appears 
to be continued through the center of T. 14 N., R. 76 W., in the Ben- 
ton, Niobrara, and Pierre beds, which are mostly' covered by Qua- 
ternary deposits. The strata also pitch steeply to the north at the 
