PALOS VERDES PENINSULA: SURVIVORS OF THE WORLD'S RICHEST COLLECTIONS OF PLEISTOCENE MARINE INVERTEBRATE FOSSILS

The Palos Verdes Peninsula, Los Angeles County, California has provided some of the richest collections of Pleistocene marine invertebrate fossils in the entire world. Most of the classic exposures are now gone or greatly reduced in outcrop area due to residential and commercial development. Exposures of Pleistocene sediments have been abundantly described in the geologic literature during the past ~150 years, but only a few exposures are still accessible. The important surviving exposures are at John S. Gibson Boulevard, 2nd Street, Timms Point and Knoll Drive in San Pedro, and the Richard R. Ball Sand Pit and Chandler Quarry in Rolling Hills Estates. The Chandler Quarry, which will soon be covered by encroaching residential development, now contains perhaps the most spectacular exposure of the San Pedro Sand and Palos Verdes Sand. The Palos Verdes Sand in the Chandler Quarry is unusual, because it has the thickest known section (~30 feet) in the Palos Verdes Peninsula with several recognizable sub-units well exposed.

The Pleistocene deposits that mainly occur along the northern flank of the Palos Verdes Hills and in San Pedro consists of middle Pleistocene Lomita Marl, Timms Point Silt and San Pedro Sand unconformably overlain by upper Pleistocene Palos Verdes Sand. The Lomita Marl contains a fossil assemblage dominated by abundant mollusks and foraminifers indicating outer sub-littoral, moderately deep cool water in the lower beds and warm shallower inner sub-littoral water in the upper beds. The Timms Point Silt contains an assemblage of abundant mollusks and common foraminifers indicating deposition at depths greater than 92 meters in cool water. The Sand Pedro Sand contains a scattered assemblage of common mollusks indicating deposition at a depth of 92 meters near base, to about 18-27 meters at top in a mostly deltaic environment. The overlying Palos Verdes Sand contains very abundant mollusks indicating deposition in warm water at depths ranging from 0 to 27 meters, which is inner sub-littoral. Of the approximately 13 terraces that step up the Palos Verdes Hills, only the youngest and lowermost three or four terraces have provided the prolific fossil finds.

Recent photographs of some of the remaining exposures and some of the fossil content will highlight this talk.