The
lava flows that form the sinuous flat-topped mesas of Table Mountain in Tuolumne County belong to a geologic formation known as the Table Mountain Latite. Within the region of Table Mountain, the Table Mountain Latite is mapped as a part of the Mehrten Formation. Further north, it is considered part of a sequence of volcanic strata known as the
Stanislaus Group. The Table Mountain Latite consists of high-
potassium trachyandesite lavas. During the
Pliocene, circa 10.4
Ma, these lavas were likely
erupted from the Little Walker Volcanic Center near
Sonora Pass. They flowed more than down a palaeo-Stanislaus River channel, known as the
Cataract Channel, and past
Knights Ferry in the
Sierra Nevada foothills. These lava flows filled the Cataract Channel and overflowed into parts of its
floodplain. Before the creation of
New Melones Lake and Lake Tulloch, the modern Stanislaus River occupied a deep gorge west of Table Mountain. Beneath the Table Mountain Latite and forming the bulk of Table Mountain are
andesitic mudflows and
conglomerates of the Mehrten Formation. They consist predominantly of
debris flow deposits (interpreted as
volcanic lahars), and
fluvial conglomerates, lithic
sandstones, and
siltstones deposited by rivers which flowed westward across the Table Mountain region. had largely reconstructed the courses of these ancient river valleys and systems cut into basement rocks and filled with the gold-bearing Auriferous gravels. Where exposed in modern valleys these channels have been extensively mined for gold by
hydraulic mining and underground they have been thoroughly explored by
drift mining. Although exceedingly rich in placer gold, they have been completely exhausted as a source of commercial placer gold in Table Mountain area. ==Ecology==