The lake existed in the valleys of the
Sacramento River and the
San Joaquin River,[2] at least as far north as the
Sutter Buttes.[3] If so, it might have had a size comparable to
Lake Michigan.[4] An alternate view presumes that the lake covered only the southern parts of the Central Valley.[5] The total surface covered by the lake amounts to about 30,000–50,000 square kilometers (12,000–19,000 sq mi).[6]Buena Vista Lake,
Kern Lake and
Tulare Lake are remnants of Lake Corcoran.[5]
The lake existed between about 758,000 and 665,000 years ago.[2] Clay deposition rates indicate that the lake lasted for 50,000 to 100,000 years,[9] and it underwent about 15 dry-wet cycles.[10] The
Lava Creek Tuff of
Yellowstone Caldera and the Bishop Tuff of the
Long Valley Caldera were deposited in the Corcoran Clay.[11] Before Lake Corcoran formed, the Central Valley was a
bay open to the south via a passage, until 2 million years ago when the bay was separated from the ocean, probably due to northwestward movement of the
Coast Ranges along the
San Andreas Fault. Subsequently, the valley was no longer a bay and alternately drained and filled with water.[7] The factors contributing to the formation of Lake Corcoran are not fully understood[12] but it appears that Great Valley drainage for most of the
Miocene epoch was to the south.[13]
Six hundred thousand years ago a new outlet formed in the present day
San Francisco Bay, where it remains today.[8] Sediments found south of San Francisco indicate that by 400,000 years ago the drainage was fully established. The overflow may have occurred at a time where
glaciers were melting and when shifts in the
jet stream during the
marine oxygen isotope stage 6 caused increased precipitation in and runoff to the Central Valley.[2][16] The overflow rapidly carved an outlet through
Carquinez Strait, probably catastrophically,[14][15] and drained the lake.[6][16] The Upper
Turbidite Unit of the
Monterey submarine fan may have formed soon after this outflow, when sediment from the former lake was carried out of its new outlet and down to
Monterey Bay by
longshore drift.[17][18]