Abstract: Variations in Depositional Settings Based on Shell Layers Found in Gravity Cores from South San Francisco Bay, CA

Roberto J. Anima, Michael M. Marlow, Paul Carlson

Sediment stratigraphy based on gravity cores collected in south San Francisco Bay suggests that shell layers can be used to discern variations in depositional environments. The core data also reflect a pattern of channels mapped using high-resolution geophysical profiles collected in the northeast side of south bay. A variation in shell layer composition, and the occurrence of articulated, in-growth position shells with whole disarticulated valves, versus only disarticulated, fragmented shells, indicate differing depositional settings. The cores also show the high productivity of the native oyster Ostrea lurida which is evidenced by numerous distinct layers scattered throughout the south bay. The shell horizons found in the cores are attributed to either in situ urial of Ostrea or to channel lag deposits associated with a buried channel system.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California