![]() ![]() These grassland slope facies record decrease in the size of the playa lakes.Ĭaran, S. Red-brown eolian loam prograded across lake sediments, and calcic soils developed on it. Episodes of lake shrinkage and more frequent exposure are recorded by reddening and formation of calcic horizons within lake muds. Organic material was partly oxidized and partly translocated down roots and cracks, and interbedded upland facies were gleyed. Eolian silt deposited on dry lake beds and clays deposited in flooded lakes were mixed by vertic soil processes during repeated wetting and drying. Decreased frequency and duration of flooding resulting in increased pedogenic modification under conditions similar to those under which modern playa lake sediments accumulate. Desiccation resulted in mudcracks and allowed deposition of eolian sand, but exposure episodes were relatively short or infrequent, and vertic soil formation, oxidation of organic material, and deflation of sand were minimal. Mud transported as suspended load was deposited from ponded water. The highstand phase is documented by wave-cut benches and lake sediments that extend beyond present lake margins. ![]() Sedimentary and soil structures show that during all phases the lakes were ephemeral, but that the duration and frequency of flooding varied, which caused variation in the relative amounts of accumulation, deflation, and soil formation. ![]() Stacked depositional cycles recognized in lake sediments record repeated phases of (1) initial highstand, (2) ephemeral lake, and (3) lake shrinkage and prolonged exposure. Sediments beneath 12 lakes were examined in 76 hollow-stem auger cores and in excavations. Ephemeral playa lakes on the Southern High Plains northeast of Amarillo, Texas, are underlain by more than 10 m of Quaternary lake deposits. ![]()
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