DEPOSITIONAL ENVIRONMENTS OF THE OLIGOCENE ALEGRIA FORMATION, SANTA BARBARA COUNTY, CALIFORNIA
The Alegria Formation was deposited mostly in a shallow-marine, wave-dominated environment. The dominant trough cross-bedded sandstone represents deposition in the upper shoreface either by longshore currents or wave currents in the breaker zone. The lenticular oyster limestone beds represent storm beds deposited by gradient currents in channels on the shoreface. The tangential cross beds and overlying conglomerate lens represent a small delta front that was overridden by a subaqueous channel deposit of a small, eastward-flowing river in very shallow marine water. Current direction is presently south, but after 90° of counterclockwise rotation is restored, original flow direction was eastward. An original eastward-flowing current direction indicates the presence of an exposed forearc ridge to the west of the site of deposition during the Oligocene. The sandstone with the thinly bedded fossil fragments was deposited in a backshore environment. Clear evidence of foreshore deposition was not observed. A persistent red mudstone that occurs near the top of the formation may represent the location of an intraformational disconformity.