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lava falls, by mass.,wasting, or simply by high flood levels. Cooley (1969:personal communication) estimated that in the absence of a damming effect, a free.,flowing Colorado river would have needed a discharge ~f about 10 mi 11i on cfs to have empl aced the log 44 m (144 feet) above stream level. However, if the Colorado River bed had been flowing at one of the Pleistocene terrace levels some 20 or even 44 m (65 or 144 feet) above the present stream level at the time the dri ftwood was deposi ted, di scharge 1 evel s woul d not have had to be so inordinately high. i ..j Pleistocene Terraces in the Little Colorado River Valley A number of workers have noted that the L ittl e Colorado Ri ver appears to be the broadest and most mature valley in the entire Colorado Plateau (Childs 1948). A whole flight of Pleistocene terraces and Pl iocene and Mi ocene erosi on surfaces have been identi fi ed here. K.,Ar dating of basalt flows ,which overlie these surfaces (Damon, Shafiquallah and Leventhal 1974) provides dating control on a number of these surfaces. In general, Cooley, Harshbarger, Akers, and Hardt (1969) recogni ze three 1 ate Pl ei stocene all uvi al terraces at about 9, 15, and 23 to 30 m (30, 50, and 75 to 100 feet) above average stream level in the Cameron.,Winslow area. These "Late Wupatki II terraces are overl ain by coarse alluvial gravels that fonna distinct desert pavement and are coated by a black patina of desert varnish. Cooley correlates these terraces wi th three gl ae; al events that occurred on the San Franci sco Peaks and thatpost.,date 212,000 years B.P. (Pewe and Updike 1976). Two IIEarly Wupatki II terraces occur at about 40 to 60+, and 60 to 90 m (150 to 100, and 200 to 300 feet) above stream level. The lower of these underlies the Tappan flow which K...Ar dates at about 0.5 million years B. P. (Damon and others 19741. The 01 der "B1 ack Point" erosi on surfaces occur at about 120 to 150 m (400 to 500 feet) and 183 to 240 m (600 to 800 feet) above stream 1 evel. The upper surface underl i es the Black Point flow which dates at about 2.4 million years B.P. Based on these dates, the Little Colorado River has been downcutting at an average rate of 90 to 100 m/million years for the last 2.4 million years (Damon and others 1974). Cooley and others (1969) estimate that while the Little Colorado River cut only about 240 m during the Black Point '" ~- f "'\ , i t-'"l LcJ 21