Natural Resources Management and Environmental Sciences Department
BS in Earth Sciences
Antonio F. Garcia
Most of the Kings River in the Sierra Nevada Mountains of California has responded to regional uplift with rapid incision, creating the deepest canyon in the United States. However, Kings Canyon near Cedar Grove is still a mountainous relict landscape with little evidence of fluvial incision. Mapping took place in the Cedar Grove area of Kings Canyon to assess factors and/or processes causing relatively low stream incision rates in the region during Holocene time. A surficial geologic map was created in the field, along with visual observations of the South Fork of the Kings River and characterization of geologic map units. The surficial map showed no evidence of knickpoint retreat and little subsequent vertical erosion near Cedar Grove. The field area has a large amount of young alluvium (unit Qa ) and a significant amount of young colluvium (unit Qc ). Tioga and Tahoe Stade moraines (unit Qm ) are present, but only as far west as Cedar Gove village. Stream terraces (unit Qoa ) exist in close proximity to the South Fork of the Kings River, but they postdate the last glaciation and are less than 10,000 years old. Minimal Holocene time fluvial incision near Cedar Grove appears to be a consequence of glaciation. Glacition lowered channel gradient and vertically denuded the valley bottom of Kings Canyon at Cedar Grove far greater than fluvial erosion would have in a comparable time scale. The Wisconsinan Glaciation also proved to be a major erosional agent and originator of sediment in the upper Kings drainage. This glaciation significantly lowered stream gradient and, consequently, stream power, and produced sufficient sediment (alluvium and till) to partially fill the scoured Kings Canyon glacial trough. Relatively fast and large magnitude Holocene time stream incision rates in areas not affected by glaciation (5 km west of Cedar Grove) support the case that Wisconsinan glaciations have proven to be a “system wrecking ball” for the Kings drainage near Cedar Grove.