This paper by M. Keegan Raines and colleagues examines the sedimentary record of ancient drainage networks as they changed in response to early mountain building in the adjacent Cordillera. The study attempts to test several hypotheses used to explain observed changes in sediment composition and to unravel predictable patterns of sediment dispersal that may be found in similar basins. The changes in sediment composition, along with geochronology, petrography, and paleocurrent measurements, are interpreted to indicate at least two distinct sediment sources entering the early Alberta Basin. One source of sediment is interpreted to be from the adjacent mountain belt, while other sediments are interpreted to be far travelled recycled sediments. This study sheds light into a classic example of a foreland basin, revealing early stages of development that have been poorly understood.
Sediment supply, base level, braiding, and bedrock river terrace formation: Arroyo Seco, California, USA
Noah J. Finnegan and Greg Balco, Dept. of Earth and Planetary Sciences, University of California, Santa Cruz, California 95064, USA. Posted online 29 Jan. 2013; http://dx.doi.org/10.1130/B30727.1.
In many settings, rivers alternate between carving wide valley bottoms (straths) and cutting narrow gorges over time, thereby creating longitudinally continuous paired bedrock strath terraces along valleys. Strath terraces are used ubiquitously in geomorphology and tectonics; however, how and why they form remain poorly understood. Noah Finnegan and Greg Balco focus on Arroyo Seco in the central California Coast Ranges, where they test hypotheses for strat
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Geological Society of America