CON ANT CREEK. 161 



conant creek. — The Carboniferous limestones of Crimson Peak south of the 

 head of Berry Creek extend down the northern spur with a dip of 7° to 10° 

 NW.j as already stated, and form the divide to Conant Creek and the creek 

 south of it; but the}' are covered with rhyolite farther north, appearing 

 beneath it in several spurs projecting into the valley at the head of Conant 

 Creek. The lower portion of the rhyolite sheet is dark colored and glassy, 

 becoming lighter colored and lithoidal higher up. On the small spurs the 

 lamination of the lava dips to the northwest, showing that the slope was in 

 this direction. On the divide between Conant Creek and the creek south 

 the limestones terminate abruptly against soft clays and sandstones, pre- 

 sumably of Cretaceous age, but of which there are no good exposures, 

 while to the south the massive limestones can be traced along a western 

 escarpment to where they overlie sandstone and gneiss, which form a group 

 of peaks northwest of the main Teton Range. 



The soft clay shales and friable sandstones on the low saddle south of 

 the head of Conant Creek dip toward the west and extend northward across 

 the basin at the head of Conant Creek. Their close proximity to the Car- 

 boniferous limestones indicates a fault and considerable displacement between 

 the two, which, however, may not exist farther north ; for west of Survey 

 Peak there is sufficient distance between the Teton formation and the north- 

 ward extension of the shales to allow of the intermediate formations being 

 in place. 



The divide between Conant Creek and the head of Boone Creek is a 

 narrow ridge composed of well-rounded gravel, mostly quartzite. This also 

 forms the lower ends of the two short spurs south. The exact relation of 

 this gravel to the adjacent rocks was not discovered. Its character and 

 general appearance are those of a recent deposit connected with the glacia- 

 tion of the region. 



volcanic breccia. — The sedimentary area is bounded on the west by an 

 accumulation of volcanic tuff-breccia that is exposed for a distance of 6 

 miles north and south, and again farther north in the neighborhood of Birch 

 Hills. The actual extent of the breccia is unknown, since it is partially 

 co\ ered by rhyolite. A portion of it has been uncovered in Berry Creek. 

 It is well exposed in the valleys cut through it by Boone and Conant creeks. 

 The rocks exhibit rude assorting, but are not bedded, the coarse agglomer- 

 ates occurring with tuffs and fine breccias without order or arrangement. 



MON XXXII, PT II 11 



