The Olive Hill Reservoir, also known as LACMNH locality 15677, is a group of beds of Miocene (Messinian stage) age dating back to 7.25 - 5.33 Ma located in Orange County, California. It is part of the Puente Shale Formation and Yorba Member. The lithology of the area is fine, filled with concretions including sponges and gray, lithified siltstone. Fossils preserved at the Olive Hill Reservoir include species of Suggrunda, Eponides, Pseudoparella, and Bolivina. Also present is the scallop Delectopecten peckhami, the ray-finned fish Scopelogadus mizolepis, and the pipefish Syngnathus avus.