Dr. Perry Ehlig’s Geologic Research Collection
Visit the California Geological Survey's Los Angeles Office to view rock specimens and thin sections collected by Dr. Ehlig.
Dr. Perry L. Ehlig was a California-registered engineering geologist, concerned primarily with landslide, groundwater, fault, and earthquake problems. He contributed significantly to the understanding of the complex regional geology of southern California, especially of basement rocks and the displacement history of the San Andreas Fault system. He scrutinized rocks in nearly every range and canyon from north of the Transverse Ranges to south of the Mexican border, with a particular focus on the San Gabriel Mountains, Mojave Desert, borders of the Salton Trough, and along several strands of the San Andreas Fault system. His forty or so publications include many papers dealing with the Vincent and related thrust systems and the origin and history of the underlying Pelona–Orocopia–Chocolate Mountain schists.
In 2021, the Ehlig family donated the rock specimens collected through his research to the California Geological Survey, along with field maps, field notes, and thin sections. Explore this special feature to learn more about his life and research, in addition to previewing the collection.
A brief biographical video of Dr. Ehlig narrated by his grandson, Evan Proffer. Photos: Kathleen Riedel
Dr. Ehlig's Research
Dr. Ehlig's investigations of the Vincent thrust system and the tectonically underlying Pelona Schist in the San Gabriel Mountains stand out among his recorded achievements. He led the way in demonstrating that the body of metagraywackes and metabasites (Pelona Schist) was laid down originally as a thick section of sediments and volcanics upon ancient-ocean floor during Jurassic and Mesozoic time, and then was carried eastward beneath a thrust system that emplaced continental rocks, viewed as part of a subduction zone.
Dr. Ehlig climbing a hillside during field research. Photo: Kathleen Riedel
He was among the first to show inverted metamorphism, with a record of higher temperatures above those somewhat cooler. He also demonstrated that earlier structural displacements, carrying the schist body downward to the east, were overprinted by those suggesting a much later reversal of shear direction. In time this led to recognizing that the uplifted and exhumed mass of schist was a type of core complex and that the uplift was related to widespread detachment faulting beneath much of southern California.
Preview part of the collection
Study areas Dr. Ehlig focused on during his extensive research included the Chilao Flat and Mount Wilson 7.5-minute Quadrangles. View his field maps, rock specimens, and thin sections of these areas using the resources below.
Explore the map to find where Dr. Ehlig collected rock samples within the Chilao Flat Quad. Toggle between the actual paper field map he used and the basemap by clicking the Layers button. Select a point to see the rock type and photos: the first photo shows the rock sample and the second shows the thin section. A thin section is a sliver of a rock sample that is mounted to a microscope slide to observe its mineral composition. Photos: CGS
Explore the map to find where Dr. Ehlig collected rock samples within the Mount Wilson Quad. Toggle between the actual paper field map he used and the basemap by clicking the Layers button. Select a point to see the rock type and photos: the first photo shows the rock sample and the second shows the thin section. A thin section is a sliver of a rock sample that is mounted to a microscope slide to observe its mineral composition. Photos: CGS
Dr. Ehlig's Field Maps
The features in the map below represent the majority of Dr. Ehlig's study areas. Select one to view a PDF attachment of his field map.
Dr. Ehlig's Field Maps
The California Geological Survey would like to thank the Ehlig family for their donation. To view the collection, please contact the CGS Los Angeles Office to set up an appointment:
cgshq@conservation.ca.gov | (213) 239-0894
