HR: 1330h
AN: OS52B-0915    [PDF]
TI: The Golden Gate Mirror Bar
AU: * Keller, B R
EM: kyrrab.cal@verizon.net
AF: Keller Hydrogeophysicist, 741 Dolores Dr., Santa Barbara, CA 93109 United States
AB: The provenance of the sand and gravel that is deposited in central San Francisco Bay appears to be mainly the nearby ocean coast, on the basis of lithologic type and grain size distribution. Outside of the Golden Gate is an arcuate sand bar called the San Francisco Bar, or historically the Golden Gate Bar. The Bar is maintained by deposition from fanning-out and slowing of ebb tidal jet currents leaving the deep, narrow throat of the Golden Gate (the paleo channel of the Sacramento River), as well as longshore drift. It is proposed that a similar mechanism operates inside the Bay, depositing sediment via fanning-out and slowing of flood tidal jet currents, called the Golden Gate Mirror Bar mechanism. Inside the Bay, the currents pass over a series of Franciscan bedrock ridges, so the form of the Mirror Bar is less regular than that of the Bar. Other sediment sources in the central Bay include longshore transport from the south, erosion of uplifted Pleistocene sand deposits, and possibly paleo tsunamis. A sediment-buried Holocene graben in the San Andreas fault zone, crossing the San Francisco Bar, indicates the possibility of local tsunamigenic faults just off the Golden Gate.
DE: 4235 Estuarine processes
DE: 4558 Sediment transport
DE: 4560 Surface waves and tides (1255)
DE: 4564 Tsunamis and storm surges
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting