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

. e. reynolds and d. m. mller
56.5 (0.6) Continue past Cherokee Road.
60.0 (0.5) TURN RIGHT (west) on Golden Desert
(power line) road.
60.8 (0.8) The road bends.
61.1 (0.3) The road bends; prepare for dips.
61.7 (0.6) Continue past deformed Lake Manix sediments.
62.0 (0.3) BEAR RIGHT (north) between legs of double
metal tower.
62.1 (0.1) BEAR RIGHT on rutted dirt road heading
east-northeast toward mining cuts on Harvard Hill.
62.2 (0.1) Cross north over ruts in road and PARK near
mining cuts for stops Q-6 and M-1.
62.7 (0.5) STOP Q-6—Harvard Hill Mining Cuts. A
Stop Q-5. Wetterman Ranch Bluffs. Two red soil profiles Pleistocene thrust fault places Miocene limestone of the
developed on two sequences of lacustrine silts and clays Barstow Formation over Pleistocene Lake Manix sedi-
between lake filling events. M. Reheis photo.
ments. Lake Manix sand, beach gravel, and minor muds
The white, fine-grained, water-laid Manix ash lies about are exposed in the pale badlands to the west. They repre-
mid-section here. These exposures will be compared to sent folded sets of beach gravels interbedded with sands.
sediment recovered in a long core taken a few hundred These beds at their highest point lie at least 50 m above
meters to the north. RETRACE to Vortac and Manix. their original level, representing significant uplift in the
late Pleistocene and Holocene. Strands of the Manix fault
50.7 (1.1) BEAR RIGHT (northwest) toward Vortac.
lie to the north and south of the outcrops, and probably
51.0 (0.3) Continue past Vortac.
intersect with the Dolores Lake fault on the west to cause
local compression. The thrust fault over the lake beds
51.3 (0.3) Slow through curves.
probably represents a more impressive manifestation of
52.4 (1.1) Slow through curves.
this same compression.
52.8 (0.4) Cross railroad tracks and stop at Yermo Road. STOP M-1—South Harvard Hill stratigraphy and
TURN LEFT (west).
structure. WALK SOUTH to the contact between a high
54.6 (1.8) Continue past the southern ridge of Lime
ridge of silicified limestone and the sands that lie to the
Hill. Note the southeast-dipping Pliocene gravels (Byers,
southwest of that ridge, then proceed upsection across
1960).
the ridge, across another ridge, and to the dark hill on the
northeast.
55.0 (0.4) Continue past a ridge supported by indurated
round-cobble conglomerate (CRC, Reynolds and others,
Key observations here are the facing directions (north-
this volume).
east) for Miocene sediments, the ~19.1 Ma age of the
white tuff underlying avalanche breccia, and correlation
56.0 (1.0) TURN LEFT (south) at Harvard Road.
of the limestone. Leslie and others (this volume) argue
that a thrust fault must lie in
this section because of older
Miocene sediment lying on
younger massive Miocene
limestone that elsewhere lies on
a 18.7 Ma tuff (Stop M-2). The
coarse conglomerate and avalanche
breccia in the Barstow
Formation here indicate prox-
Stop Q-6. South Harvard Hill. Branches of the Manix Fault thrust Miocene sediments of
imity to a steep basin margin to
the Barstow Formation over late Pleistocene Manix Lake sediments.
10 2010 Desert Symposium