TAPHONOMY OF BARNACLE AND FISH SHORELINE ACCUMULATIONS OF THE SALTON SEA, CALIFORNIA, USA

From 1905-067, the Salton sink was flooded by Colorado River water. Since the flooding event, the closed lake system level has been maintained largely by agricultural runoff and river inflow. The closed basin experiences high evaporation rates causing an increase in salinity and eutrophic conditions which prompt an evolving ecosystem. However, massive die-offs have removed all fish except the hybrid tilapia (Oreochromis mossambicus x O. uroepis) and the barnacle (Balanus amphirite). As a result, tilapia and barnacles dominate the Salton Sea shoreline sediments.

During high wind events, overturning of the stratified water column generates algal blooms reducing dissolved oxygen and stirring up phosphates and sulfides causing high mortality events in the tilapia population and break barnacles off their substrates. This study reports on the application of a semi-quantitative fish articulation scale that describes the fish kill and barnacle preservation across the shoreline.

We developed a semi-quantitative scale that varies from 1 to 5; each integer reflects an increase from whole to total fish disarticulation. Barnacles were described as clustered (two or more attached to one another), whole, or crushed. An overall trend from articulation to disarticulation occurs from the shoreline to the backshore. The storm high-water line reflects the maximum articulation and predation of fish and the occurrence of clustered barnacles. In the swash zone barnacles are reduced from clusters to whole to crushed. On high lake-level beach ridges, barnacles and fish parts form low-angle, lake-ward dipping foresets. Rare landward dipping forests are present and record storm wash over. Storm washover fans are well developed along some portion of the shoreline and dominated by clastics, crushed barnacles, and abundant skeletal tilapia parts. This assessment permits us to study a rare biological, rather than clastic, dominated lacustrine shoreline and can be applied to preserved deposits in the rock record.