Flood Deposits, Bijou Creek, Colorado, June 1965

摘要: ABSTRACT A study was made to determine the character of deposits a major flood along Bijou Creek, Colorado. These consist sand that laid down in mid-June, 1965 during rapid movement upper flow regime. They are composed largely horizontal or nearly layers cover channel and extend outward beyond banks on each side stream commonly for distances one-quarter one-half mile more. Typical thickness these ranges from two three feet, but maximum 12 feet measured at one place West Creek. Estimates indicate strata constitute 90 95 percent all deposits. The second most common structure plains is tabular planar type crossbedding formed foresets developed mostly outer margins depositional sheets. Apparently such structures where water had lost some its force deposited sloping sediment front. Other locally include climbing ripple laminae convolute bedding, which waning stages deposition apparently characteristic relatively sheltered areas away path main flood. dominant grade size represented by Creek deposits, based mechanical analyses 137 samples four localities studied, medium grained (0.5-0.25 mm); 51 were this class; 37 dominantly fine grained; 36 coarse grained. very large objects, as beams concrete slabs bridges, storm velocity well above necessary carry sand; grain probably determined particles available source area few miles south. Sorting fair samples; it good only seven poor ten. Data structure, texture, shape bodies floods proportions should be useful interpreting ancient comparable environment. Also, they help relating types recognizable deposit specific stage deposition, regime, distinguishing river those adjacent plains.