Page 278 - 1915, Springs of CA.

258 SPRINGS OF CALIFORNIA.
The rocks of the region are shales and sandstones, which are in
some places considerably silicified, but the springs apparently
issue from soft sandstone that overlies a bed of harder sedimentary
material. Their small flows indicate that they are supplied by
water of essentially surface origin, which becomes slightly mineral-
ized from the shales and sandstones and is brought to the surface
on the side of the ravine by a bed of relatively impervious material.

STJLPHTJR SPRINGS IN FRANZ VALLEY (SONOMA 12).

Franz Valley lies about 15 miles north of Santa Rosa, between
that place and Calistoga. Two small sulphur springs in it are
occasionally used as drinking springs by outing parties to the Petrified
Forest, a small group of silicified tree trunks a few miles distant. The
springs are probably similar in character to those at Mark West Warm
Springs (Sonoma 11, p. 115), which are a few miles westward. Small
undeveloped sulphur springs issue at a number of other places in the
counties north of San Francisco and San Pablo bays. Among them
is one in Lucas Valley, a few miles northwest of San Rafael, but it
has been known only locally and is seldom visited.

STJLPHTJR SPRING NEAR LITTLE STJLPHTJR CREEK (SONOMA 6).
Near Little Sulphur Creek, about 7 miles northeast of Geyserville,
on property that has been open for a few years as a summer resort
under the name of Geyser Peak Ranch, is a spring that yields a small
flow of cool, distinctly sulphureted water. It has been used only
for drinking.
The rocks at this locality are tJie shales and coarser sediments
that constitute the greater part of the coastal ranges of the region.
STJLPHTJR SPRING NEAR STJLPHTJR CREEK (SONOMA 3).
A small cool sulphur spring which is about 3 miles northeast of
Cloverdale, on the road to The Geysers (Sonoma 4, p. 83), rises in the
bottom of a ravine tributary to Sulphur Creek and a few yards
above the road. The spring has not been improved and is some-
times covered by landslide material, but when open it yields moder-
ately sulphureted water and forms a roadside drinking spring.
The rocks of the locality consist of serpentine and of dark altered
sandstone which probably belongs to the Franciscan formation.
The spring apparently issues from crevices in a crushed zone in the
sandstone.
STJLPHTJR SPRINGS ON BRANCH OF DEEP CREEK (MENDOCINO 12).
Mildly sulphureted water issues from several vents in the bed and
along the bank of a branch of Deep Creek, on the eastern side of
Willits Valley about 4 miles east of Willits. The yield is apparently