MANSFIELD: POST-PLEISTOCENE DRAINAGE. 
traced in the ancient gravels, 
the lower perhaps fifty feet 
below the higher. Both ter- 
races may be clearly seen on 
the south side of the valley 
but the lower terrace is not 
so evident on the north side. 
The observer who stands on 
the north side of the valley, 
opposite Pillar Peak, may 
see the top line of the upper 
terrace stretching east and 
west, almost unbroken. The 
lower terrace level is less per- 
fectly preserved but it may 
be traced along the hill-tops. 
The slopes ascending from 
the upper terrace are not very 
steep and break above into 
more gentle grades at a fairly 
well defined shoulder. The 
tributary streams, such as 
Two Bit and Pedee, have 
broad, V-shaped valleys that 
exhibit this feature very clear- 
ly. Above the higher, more 
gentle slopes occur residual 
knobs, such as the rocky sum- 
mit of Pillar Peak. The 
ancient valley, of which the 
upper terrace formed the 
floor, is broadly open, has 
gentle slopes and relatively 
straight sides, features indica- 
* tive of late maturity. This 
valley, however, has appar- 
ently been incised and opened 
in the floor of a still more 
ancient valley, for the shoul- 
der, above indicated, points 
to more than one period of 
incision. The more gentle 
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