MANSFIELD: POST-PLEISTOCENE DRAINAGE. 83 
represented in Figure 8), where all are shown, occurs at the mouth of 
Big Goose Canyon (Plate 4). Big Goose Creek, the master con- 
sequent stream, has carved its V-shaped gateway nearly one thousand 
feet below the shoulder, which marks the junction of the newer and 
older slopes on its valley side (Figure 9) and still rushes, as a foaming 
torrent, over an uneven and bouldery bed. The opportunity thus 
given for the development of drainage, adjusted to structure, is great. 
The Red Canyon. A subsequent tributary enters the creek from 
the south just after its emergence from the front rampart. ‘This 
tributary, by gnawing headward for a mile and a half along the strike 
of the rocks, has carved for itself in the soft red beds of the Chug- 
water formation (Darton b, p. 397) a deep canyon. The rich, red 
Fia. 9. The gateway of Big Goose Creek from the north. 
color of the sandstones and shales, interrupted by white streaks, caused 
by lenses of gypsum, and by a narrow purplish band, due to the pres- 
ence of a thin bedded, fine textured limestone near the bottom of the 
series, is displayed continuously on the east side of the canyon, where 
the wall in many places is almost sheer in its descent, and lends to 
the canyon an appearance of striking beauty. On account of the 
strong monoclinal dip of the strata eastward, there has been mono- 
clinal shifting, concomitant withincision. The shifting began and con- 
tinued for some time along the dip of the thin bedded limestone just 
mentioned; but the limestone has finally been cut through and the 
stream is now working on the weaker red sandstones beneath it. The 
result of the shifting has been to produce on the east side a steep and, 
in places, precipitous wall, while on the west side the slope, stripped 
