6: A Brief Geologic History of California
- Page ID
- 20339
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Geologists are historians that have a story to tell that is incredibly broad in both space and time. Geologists are also detectives that must search for the evidence and clues to the tectonic past. Often, subsequent geologic events obscure the evidence we are looking for in many ways: rocks are buried and no longer exposed at the surface, rocks are metamorphosed and may no longer look like the original rocks or have the same chemistry, tectonic processes can transport rocks great distances so they are no longer in the same place where they formed, subduction zones can return entire ocean basins to the mantle well beyond our view. While these physical and chemical changes obscure the original properties of the rocks, they are part of the story of how the rocks came to be where we see them today. Geologists are trained to identify these changes to rocks and what they mean about the environment the rock was formed in. Geologists then put these environments and events in chronological order based on cross cutting relationships or absolute ages.
In this chapter we will look at a broad overview of how the tectonic plates interacting along the western margin of North America have changed through time. We will also look at time slices of the geologic map of California to see how the geologic environment has changed through time and understand the evidence used to unravel the geologic past.
Table \(\PageIndex{1}\) summarizes the major geologic events that shaped California into what we see today. Like many geologic timescales, this table is organized with the oldest events at the bottom and youngest events at the top. This chapter presents a chronologic account of these major geologic events with each of the following pages detailing a different geologic era. This chapter acts as the temporal link between the various geological provinces presented in the following chapters. For more detailed information on the geology of a specific region, the reader should consult the relevant geomorphic province chapter.
| Era | Period | Epoch | Major Geologic Events |
|---|---|---|---|
| Cenozoic (66 Ma - present) | Quaternary (3 Ma - present) | Holocene | Last glacial maximum ~20,000 years ago. Volcanoes erupt in the high Cascades |
| Pleistocene | Cascade volcanoes develop | ||
| Neogene (23 - 3 Ma) | Pliocene (5 - 3 Ma) |
Sutter Buttes volcanoes erupt Sediments eroded from the Sierra Nevada and Coast Range are deposited into the Great Valley |
|
| Miocene (23 - 5 Ma) | Basin and Range extension begins (continues to today) | ||
| Paleogene (66 - 23 Ma) | Oligocene (34 - 23 Ma) | Spreading center is subducted and the San Andreas Fault begins to develop | |
| Eocene (56 - 36 Ma) | Laramide Orogeny ends | ||
| Paleocene (66 - 56 Ma) | |||
| Mesozoic (251 - 66 Ma) | Cretaceous (145 - 66 Ma) |
Sierra Nevada sediments begin to fill Great Valley Klamath terrane accretes onto N. America Laramide Orogeny begins |
|
| Sevier Orogeny | |||
| Jurassic (201 - 545 Ma) | Nevadan Orogeny | ||
| Supercontinent Pangaea begins to rift apart | |||
| Sonoma Orogeny | |||
| Triassic (251 - 201 Ma) | Subduction of the Farallon plate | ||
| Paleozoic (539 - 251 Ma) | Permian (299 - 252 Ma) | ||
| Pennsylvanian (323 - 299 Ma) | |||
| Mississippian (359 - 323 Ma) | Antler Orogeny | ||
| Devonian (416 - 359 Ma) | California was mainly a passive margin | ||
| Silurian (444 - 416 Ma) | |||
| Ordovician (485 - 444 Ma) | |||
| Cambrian (541 - 485 Ma) | |||
| Proterozoic (2,500 - 539 Ma) | Neoproterozoic (1,000 - 541 Ma) | Supercontinent Rodinia begins to rift apart | |
| Mesoproterozoic (1,600 - 1,000 Ma) | Abundant carbonate rocks | ||
| Paleoproterozoic (2,500 - 1,600 Ma) | Oldest rocks in California form |
An interactive version of the 2020 time scale is available in the back matter of this text.
*The dates on the table above are based on v2023/09 of the International Chronostratigraphic Chart from the International Commission on Stratigraphy. The latest version can be found on the ICS website.
By the end of this chapter, you should be able to:
- Describe the evidence used to recreate the past tectonic environments in California.
- Describe the tectonic setting of the Precambrian, Paleozoic, Mesozoic, and Cenozoic stages of development of California geology.
- Identify modern tectonic settings that we can use as analogs to understand the processes that created the geology of California.
- 6.1: Developing a Geologic History
- Learning how to read the rock record as a way of discerning the evolution of the Earth
- 6.2: Proterozoic Eon
- An ancient time when the shape of the Earth's continents was utterly unfamiliar
- 6.3: Paleozoic Era (540 – 250 Ma)
- California begins to be constructed, one giant collision at a time
- 6.4: Mesozoic Era (250 – 66 Ma)
- Orogenies, orogenies, orogenies... and the formation of the Sierra Nevada
- 6.5: Cenozoic Era (66 Ma – Present)
- California begins to take a familiar shape in the Cenozoic
- 6.6: Chapter Summary
- A summary of A Brief Geologic History of California.
References
- Cohen, K.M., Harper, D.A.T., Gibbard, P.L. 2024. ICS International Chronostratigraphic Chart 2023/09. International Commission on Stratigraphy, IUGS. www.stratigraphy.org (visited: 2024/10/18)
- California's Amazing Geology, 2nd, by Donald Prothero, 1032294906.
- Roadside Geology of Northern California, by David Alt and Donald Hyndman, 0878426701.
- Roadside Geology of Southern California, by Arthur Sylvester and Elizabeth Gans, 0878426531.
Thumbnail: "Northeast Pacific and Western North American Plate Tectonic History, animation" by Tanya Atwater is licensed under CC-BY-NC 4.0.