14.6: Mineral and Petroleum Resources of the Transverse Ranges Province

Petroleum, Natural Asphalt Seeps and the La Brea Tar Pits

Courtesy of the extensive basin deposits throughout the Transverse Ranges Province, oil and gas production is widespread. To learn more about the geologic origin and processes behind the formation of oil and gas, see 12: Great Valley.

Due to deformation of basin sediments throughout the Transverse Ranges Provinces, circumstances are just right for the preservation of valuable oil and gas reserves. The widespread oil source rock here (the Monterey Formation and its equivalents) is found in virtually every basin. Transpressional folding and faulting of basin units have created structural traps for oil, and lithologies are present to not only store the oil (for example the Sespe formation), but also cap it and prevent additional migration (for example, the Rincon Formation).

Major oil fields are found throughout this region (Figure \(\PageIndex{1}\)). In the LA Basin, oil fields lie along two northwest striking trends. The southernmost of these extends from the region north of Huntington Beach through the northeast edge of the Palos Verdes Peninsula and northward to the area of Santa Monica. The northern trend extends from north of Anaheim through downtown Los Angeles and slightly where it meets the southern trend. In the Ventura Basin, oil fields generally lie along an east west striking trend that extends offshore to the area south of Santa Barbara and inland as far as the area around Santa Clarita.

These trends generally parallel major fault systems and fold structures in the region (see: 14.4: Cenozoic Sedimentation and Basin Development).

Figure \(\PageIndex{1}\):Map of oil fields in the Transverse Ranges Province. Areas of oil production are shown in gray shaded zones and locations are described in the text. "Los Angeles Field Locations" by Antandrus is licensed under CC BY-SA 3.0

The Wilmington Field, which trends northwest and is located to the northeast of the Palos Verdes Peninsula (Figure \(\PageIndex{2}\)), beginning the Torrance area and continuing southeast to the region of Belmont, roughly 16 km (10 miles) in length and 8 km (5 miles) at its widest point. This field is an important element of the oil production in this region and has been in operation since 1932 and is the third largest oil field in the US in terms of total oil production. Once oil production initiated in this region in the late 1800's, oil infrastructure expanded everywhere. Oil derricks sprouted across the region (Figure \(\PageIndex{3}\)).

Figure \(\PageIndex{2}\): Wilmington Oil Field within the Los Angeles Basin. This field is northeast of the Palos Verdes Peninsula and is continuous with the Torrance Oil Field to the northwest. "Wilmington Oil Field" by Antandrus is licensed under CC BY-SA 3.0.

Figure \(\PageIndex{3}\): Two men standing near a wooden shed in the midst of dozens of oil derricks in a Los Angeles oil field. Court Street and Toluca Street, 1904. A large wooden vat is at left. These wells had been producing for over 40 years when this image was taken (1904). "Two men standing near a wooden shed" is licensed under public domain.

Oil infrastructure is not needed to find signs of oil in this region, however. For example, the La Brea Tar Pits is a by-product of this abundant resource in the Transverse Ranges. The tar pits are a natural asphalt (or “brea” in Spanish) seep. This pond of fluid asphalt has trapped and preserved an incredible number of animal fossils dating back 38,000 years (Figure \(\PageIndex{4}\)).

Figure \(\PageIndex{4}\): Bubbles of gas emerge from the top of the fluid asphalt deposits at the La Brea Tar Pits. "Tar bubble, La Brea CA" by Daniel Schwen is licensed under CC BY-SA 2.5.

Natural petroleum seeps occur in basins throughout the Transverse Ranges Province and offshore. In fact, it’s not uncommon for visitors to beaches in this region to get tar on their feet or clothing. This is because of submarine seeps that wash ashore and the occasional outcrops of reservoir rocks along the coastal cliffs (Figure \(\PageIndex{5}\)).

Figure \(\PageIndex{5}\): Tar sandstone from the Monterey Formation of Miocene age (10 to 12 million years old), of southern California, USA. "Tar Sandstone California" by James St. John (jsj1771) is licensed under CC BY 2.0.

The local Chumash and Tongva people, Indigenous inhabitants across this region exploited this resource, using it to seal boats.

Inset Box \(\PageIndex{1}\) Camouflaging Oil Production in the City

While large oil derricks no longer exist, there is still abundant evidence of active oil and gas production across this region. However, in order to reduce community objections, many of these areas are camouflaged.

For example, the THUMS facility offshore of Long Beach consists of four artificial islands that were designed to camouflage the work that goes on there. Also called “Astronaut Islands” in honor of NASA astronauts who lost their lives, these islands hide drilling rigs and other oil production infrastructure (Inset Figure \(\PageIndex{1}\)).

Inset Figure \(\PageIndex{1}\): One of the four THUMS artificial islands near Long Beach Harbor. These islands contain generic buildings designed to hide oil production infrastructure. The name, THUMS, is an acronym based on the first letter of the companies that constructed them: Texaco, Humble, Unocal, Mobile, and Shell. "THUMS Oil Island" by donielle, is licensed under, CC BY-SA 2.0.

Another example of a camouflage oil facility is found in west Los Angeles (Inset Figure \(\PageIndex{2}\)). This facility is creatively built to look like a building with a tower-possibly a church? But it hides equipment that taps the underlying Beverly Hills Oil Field!

Inset Figure \(\PageIndex{2}\): The Brietburn Drilling Rig in Beverly Hills. This camouflage rig looks like a tower; it actually hides oil production equipment that taps the Beverly Hills Field. "Breitburn Drilling Rig" by Pi3.124, is licensed under CC BY-SA 3.0.

Mining in the Transverse Ranges Province

In addition to oil and gas, other natural geologic resources include precious metals (Gold and Silver), barite and gypsum, and sand and gravel quarrying. While precious metals are not widespread, they do occur in the crystalline basement rocks of the San Gabriel and San Bernardino Mountains, and aficionados spend time panning for gold in the rivers of these ranges today. In the case of barite, gypsum and sand and gravel, these are all resources derived from the extensive sedimentary basins in this area. Sand and gravel mines can be found in the alluvial fans that flank the larger ranges.

References

1. Harden, D. R. (2004). California Geology. Pearson Prentice Hall.
2. Ingersoll, R. V., & Ernst, W. G. (1987). Cenozoic Basin Development of Coastal California (R. V. Ingersoll & W. G. Ernst, Eds.). Prentice-Hall.
3. La Brea Tar Pits. (n.d.). UCMP Berkeley. Retrieved February 15, 2024, from https://ucmp.berkeley.edu/quaternary/labrea.html
4. Malinconico, M. L. (2015). Carbonacea. NA. https://carbonacea.blogspot.com/2015/08/los-angeles-basin-most-prolific-and.html
5. Norris, R. M., & Webb, R. W. (1976). Geology of California. Wiley.
6. Wilmington Oil Field. (n.d.). Wikipedia. Retrieved February 15, 2024, from https://en.Wikipedia.org/wiki/Wilmington_Oil_Field
7. Yeats, R. S., & Grigsby, R. B. (1987). Ventura Avenue anticline: Amphitheater locality, California. In Cordilleran Section of the Geological Society of America Centennial Field Guide (Vol. 1, pp. 219-224). Geological Society of America.
8. Yerkes, R. F., McCulloh, T. H., Schoellhamer, J. E., & Vedder, J. G. (1965). Geology of the Los Angeles Basin, California-an Introduction. USGS.