2010 Overboard in the Mojave - Biological Science - California State ...

of borate minerals during the very
early 20th century and ruins of
mines, railroads, and dwellings
testify to the importance of the
mining industry at this location.
CONVENE at the Desert Studies
Center with a full tank of gas. Enter
westbound I-15 toward Minneola
Road.
0.0 (0.0) EXIT at Minneola Road.
Re-set odometer.
0.3 (0.3) Stop at Minneola Road.
TURN RIGHT (north). The road
will bear east.
0.9 (0.6) Continue past a left
turn to the landfill and the Calico
Mountains Archaeological Site .
1.1 (0.2) BEAR RIGHT. When
pavement ends, take the middle
power line access road and bear
northeast.
1.3 (0.2) Avoid the left turn.
1.4 (0.1) BEAR LEFT on power line road.
2.3 (0.9) STOP M-5—Toomey Hills. PARK in open
area north of road. The Barstow Formation is exposed on
the north side of the Manix fault, as it is at Harvard Hill.
Near the base of the section are fluvial gravels with wellrounded
clasts and tubular stromatolites (CRC, Reynolds
and others, this volume) in a section of sandstone cemented
by calcite. Above are fine-grained lacustrine sandy
silt beds interlaced with tuffs. This outcrop produced fossil
mammals which document the 16 Ma transition from
the Hemingfordian to Barstovian NALMA (Woodburne,
1991; Woodburne and Reynolds, this volume; Tedford
and others, 2004). A local sequence of beds (CRC,
Emerald Tuff, Lime Tuff) allow the Toomey sequence to
be correlated with a datable section in the Yermo Hills to
the northwest (Miller and others this volume). The crest
of the ridge here is a thick, strongly cemented soil, above
which is the Pliocene–Pleistocene Yermo Gravel. RE-
TRACE toward Minneola Road.
3.6 (1.3) TURN RIGHT (north) at road to the county
landfill and Calico Mountains Archaeological Site.
4.8 (1.2) TURN LEFT (west) away from entrance to the
Calico site and landfill.
5.6 (0.8) TURN RIGHT (north) into Emerald Basin.
r. e. reynolds and d. m. mller
Stop M-6. Yermo Hills, showing lime-green sandstone and 15.3 Ma ash layer.
6.0 (0.3) PARK in open area, avoiding nails from burnt
wood.
STOP M-6—Overview of Emerald Basin in the Yermo
Hills. This section contains a sequence of beds (CRC,
Emerald Tuff, Lime Tuff) similar to the Toomey Hills.
A dated tuff near the top of the section is about 15.3
Ma (Miller and others, this volume). If the CRC here is
equivalent to the CRC at the 16+ Ma Toomey Hills stop,
then the gray siltstone section represents at least 0.7 Ma.
A thick, silicified limestone on the ridge line can be traced
westward into the eastern Calico Mountains where it
overlies the 16.2+ Ma BPL. Retrace to main dirt road and
proceed northwest.
6.1 (0.2) TURN RIGHT (northwest) onto main dirt
road and proceed northwest.
7.0 (0.9) Join the pole line road and proceed north. This
road coincides with the approximate position of the
north-trending Tin Can Alley fault, described and named
by Dudash (2006). It is a right-lateral fault that in places
exhibits scarps cutting Holocene materials.
7.2 (0.2) TURN LEFT (west) onto Mule Canyon Road.
8.3 (1.1) Continue past the Sulfur Hole quarry in the
BPL which produced an unusual assemblage of hydrous
iron sulfate minerals oxide products from pyrite deposited
by hot springs (Dunning and Copper, 2002; Schuiling,
1999).
14 2010 Desert Symposium