August 1, 2015.
The primary purpose of this study is to better understand how climate affects river dynamics. It is also important to understand the relationship between glaciers and the transportation of sediments, as this allows us to study changes in transport through time. The studied sediments were gathered from outcrops located in Fresno Ca, off of Friant road. The origin of these sediments are the Sierra Nevada Mountains. Mesozoic metasedimentary and metavolcanic sediments are derived from the foothills, while the granitic sediments are derived from higher up in the mountains. The sediments are characterized by both their degree of rounding, and their composition. Sediments with more rounded appearance suggest a higher degree of mechanical weathering. Roundness may also suggest a longer distance traveled, than those with a more angular shape. Various sample sizes were assessed, specifically sizes -2phi(4mm) and -3phi(8mm). The composition of these samples were identified and noted as either granitic in nature or metamorphic. Geologic maps were examined to determine potential sources of a particular composition of rock. Granitic rock is found at higher elevations in the mountains, and metamorphic rock towards the lower elevations, closer to the valley. If the majority of samples are found to be granitic, a glacier may have increased the sediment supply from higher elevations. Conversely, if the majority of the samples are metamorphic, we can conclude that the dynamic river system plays the most profound role in the transport and supply of rock sediments. Ideally, this study will help identify the onset and retreat of glaciers through time.
Geology | Sedimentology | Stratigraphy
California State University, Fresno (CSU Fresno)
This material is based upon work supported by the National Science Foundation under Grant No. 1340110 and is made possible with contributions from the S.D. Bechtel Jr. Foundation, Howard Hughes Medical Institute, Chevron Corporation, National Marine Sanctuary Foundation, and from the host research center. Any opinions, findings, and conclusions or recommendations expressed in this material are solely those of the authors. The STAR Program is administered by the Cal Poly Center for Excellence in STEM Education on behalf of the California State University system.