35°41"

35° 40'

a USGS

U.S. Department of the Interior

science for a changing world U.S. Geological Survey
117°26'
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117°26'
Base fom U.S. Geological Survey, 1:62,500,
Searles Lake, 1949
Polyconic Projection
CORRELATION OF MAP UNITS
= =
all p> Holocene
sd
<
> QUATERNARY

bu

> Pleistocene

or Pliocene | or TERTIARY

| Pleistocene | QUATERNARY,

retin PRE-TERTIARY

Base fom U.S. Geological Survey, 1:62,500,

Searles Lake, 1949
Polyconic Projection

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‘Any use of trade, product, or firm names in this publication is for
descriptive purposes only and does not imply endorsement by the

US. Government

117°28'

117°28'

[See plate 1 for map location. Searles Lake Formation is a newly accepted formation described in
the text. Note unit names may change from map to map]

ws Windblown sand and colluvium (uppermost Holocene)—Windblown sand mixed
with pebbly colluvium; forms sheet
Silt (uppermost Holocene)—Playa-surface sediment

al Alluvium (uppermost Holocene)—Gravel and sand, frequently active

coal Older alluvium (upper and middle Holocene)—Medium to coarse sand, some
pebbles; inactive; surfaces smooth and nearly free of channels
Searles Lake Formation (middle Holocene to upper Pleistocene)

Unit D (middle Holocene)

Gravel and sand—Mostly near-shore lacustrine deposits but some are colluvial or
alluvial; dark angular fragments in a matrix of sand and silt; represented in many
places by scattered lag gravel
Sand and silt—Lacustrine deposits; tan to gray-orange; forms puffy surfaces,
commonly cemented by halite

Unit CD (lower Holocene)

Sand and gravel—Alluvial and colluvial deposits; light- to dark-orange-gray sand
and fine gravel; commonly has slightly orange pebbly lag gravel on surface;
locally contains reworked(?) snails and clams

Unit C (upper Pleistocene)

Clay and sand—Lacustrine deposits; grayish-green; plastic when moist; clay is
faintly bedded (color variations) but unlaminated; interbeds of sand locally grade
upward into thicker beds of fine to medium sand that is well sorted and bedded;
locally disconformable with underlying unit

Silt and clay—Lacustrine deposits; white on weathered surface, grayish-green on
fresh surface; characterized by thin white aragonite laminae; orange tuff(?) zone
near base; contains ostracodes and molluscs in west half of map area
Sand—Lacustrine deposits; tan, locally orange; medium to coarse, well-sorted,
deltaic bedding common; locally contains molluscs

17°25! 117924"
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17°25 117924!
DESCRIPTION OF MAP UNITS Silt and clay—Lacustrine deposits; white on weathered surface, grayish-green on fresh

surface; laminated to thinly bedded, gypsum crystals common; thin orange tuff(?) bed 1
to 3 m above base; contains ostracodes and molluscs in western half of map area
Gravel—Lacustrine deposits; dark-brown on weathered surfaces, pebble-sized
fragments, well sorted and rounded

Unit BC (upper Pleistocene)

Sand and gravel—Mostly lacustrine deposits, some alluvial zones; tan to orange;
sand coarse to very coarse, commonly displays pronounced deltaic structures;
brown nodose tufa common along basal contact; soil developed on upper surface
Gravel—Lag gravel deposited on surfaces when shorelines of this age were carved
on older alluvial gravels; fragments are cobble and boulder sizes, abundant nodose
tufa fragments; soil developed on upper surface

Unit B (upper Pleistocene)

Silt—Greenish-gray; thinly bedded; scattered snails and clams

Sand—Medium to coarse; tan; grading down to silt and very fine sand; greenish-
gray; prominently laminated

Sand—Very fine to medium sand grading down to silt; laminated; sand highly
calcareous; unit notably lenticular

Sand—Fine grained; gray-orange; ripple marks
Silt and sand—Massive; greenish-gray; very fine sand
Sand—Medium-orange; some ulexite, snails, and clams

Silt grading up to sand—Lacustrine deposits; greenish-orange to greenish-gray,

micaceous sand is medium to fine, very well sorted, poorly bedded; silt grades

upward to sand

Gravel—Lacustrine deposits; weathers dark-gray to brown; composed of angular to

rounded pebbles and cobbles; some sand; highly calcareous; unit notably lenticular
Unit AB (upper Pleistocene)

Gravel and sand—Mostly lacustrine deposits, some alluvial or lag gravels;
grayish-orange; orange hues especially intense in upper 0.5 to 2 m; locally, a 0.3-1 m
bed of greenish lacustrine silt and sand in middle of unit

Plate 3A—Poison Canyon

35°39'

CORRELATION OF MAP UNITS

ws al

> Holocene
coal
> QUATERNARY
>Pleistocene
4 4

[3 | Pleistocene | QUATERNARY

[ or Pliocene [ or TERTIARY

bu Pre-Tertiary + PRE-TERTIARY
Geology mapped by G.I. Smith, 1961-1970, 1983-1996
Digital database by J.E. Robinson
Digital cartography by J.E. Robinson and Richard Koch
Edited by J.L. Zigl
ited by JL Zigler Plate 3B—Salt Wells Valley
SCALE 1:10 000
V2 4 oO 1/2 MILE
500 ) 500 1000 1500 2000 2500 3000 3500 FEET
12% ———— 1
5 oO 5 KILOMETER

—

TRUE NORTH

APPROXIMATE MEAN
DECLINATION, 2009

CONTOUR INTERVAL 40 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1927

Geologic Maps of Poison Canyon and Salt Wells Valley

By
George I. Smith
2009

Professional Paper 1727

Plate 3 of 4
117°23'
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117°23'

Geology mapped by G.|. Smith, 1961-1970,
1983-1996

Digital database by J.E. Robinson

Digital cartography by J.E. Robinson and
Richard Koch

Edited by J.L. Zigler

Sand and silt—Lacustrine deposits; greenish gray to tan; numerous resistant,
fine-sand lenses mostly <15 cm thick; 0.2-3 m of indurated white silt at base
Sand—Lacustrine deposits; tan to yellowish gray in some areas, orange in others;
very coarse, prominent gravel layer at top locally contains molluscs and ulexite
Silt—Lacustrine deposits; white in lower part, greenish in upper part; nodose tufa
layer and orange tuff(?) layer one-third up section
Sand—Lacustrine deposits; orange to tan; medium to very coarse; locally fine;
some interbeds of silt; concentration of pebbles and molluscs at top contact
Silt and sand—Lacustrine deposits; tan to green; sand very fine; massive to faint
bedding
Sand—Lacustrine deposits; tan, locally orange or brown; fine to very coarse;
gravel layers at base and top of unit; some molluscs

Unit A (upper Pleistocene)

Silt and sand—Lacustrine deposits; weathers very light green to white; sand is
fine; massive to faintly bedded; near north edge of this map, member consists of
alternating lacustrine sand and alluvial gravel; calcareous soils developed on and
in upper part of unit
Gravel—Lacustrine deposits; weathers dark-brown to gray; well rounded, well
sorted, pebble to boulder; massive; deposits include lag gravels on surfaces of
older gravels with shorelines of this age carved on them

Tufa, undivided (upper Pleistocene)—Lacustrine deposits; tufa; brown nodose
(aragonite) tufa; overlies tan lattice-textured (calcite) tufa

Older gravel (middle to lower Pleistocene or Pliocene)

Alluvial deposits—Weathers to dark-orange-brown; pebble to cobble-sized
fragments are angular to subangular; soil development variable
Alluvial deposits—Weathers to very dark gray or brown; cobble to boulder-sized
fragments are subangular to subrounded; local strongly developed calcic soil
Bedrock (pre-Tertiary)—Undifferentiated bedrock, mostly plutonic types, some dikes

os
co

Contact—Queried where gradational or poorly exposed

Tufa-lined channels

10> Strike and dip of beds

DESCRIPTION OF MAP UNITS

[See plate 1 for map location. Searles Lake Formation is a newly accepted formation described in
the text. Note unit names may change from map to map]

ws Windblown sand and colluvium (uppermost Holocene)—Windblown sand mixed
with colluvial pebbles

al Alluvium (uppermost Holocene)—Gravel and sand, in active channel

cal Older alluvium (upper and middle Holocene)—Medium to coarse sand, some

pebbles, inactive, forms smooth, nearly channel-free inactive surfaces
Searles Lake Formation (middle Holocene to upper Pleistocene)

Unit C (upper Pleistocene)

Sand and gravel—Lacustrine deposits; gray; sand is medium to very coarse,
moderately well sorted; gravel is fine; weak lag gravel developed on surfaces;
fragments and beds of nodose tufa locally present
Sand—Lacustrine deposits; grayish-orange; deltaic bedding; locally a thin bed
of nearly white very fine sand near top
Silt and sand—Lacustrine deposits; light-green, calcareous, oolitic, massive to
faintly bedded
Sand—Lacustrine deposits; grayish-orange, fine to coarse, well sorted; foreset
beds common; a 1-m-thick silt layer locally in middle of unit
Silt and gravel—Lacustrine deposits; mostly green calcareous silt, gypsiferous
in upper part; poorly bedded; some pebble gravels; aragonitic nodose tufa locally
deposited on underlying surfaces prior to deposition of unit

Unit B (upper Pleistocene)

Silt, sand, and gravel—Lacustrine deposits; silt and fine sand, grayish-green; thin
bedded but not laminated; contains dark-brown organic(?) fragments, numerous
mud-crack structures; locally fractured and contorted; coarse sand beds are orange-
gray to yellowish-gray, 10 to 50 cm thick; gravel is yellowish-gray, well bedded;
rounded fragments as much as 2 cm long form 5—20% of strata

Unit AB (upper Pleistocene)

Gravel—Alluvial and lake-transported deposits; upper 10-20 cm of gravel
generally stained dark-orange-brown; composed mostly of subangular to
subrounded fragments of hypabyssal dike rocks, as much as 15 cm across, that in
places were transported horizontally by currents in a lake; unit forms a cap on the
bar in northeast corner of map; moderately strong calcareous soil locally
developed on surfaces
Sand and silt—Lacustrine with some thin alluvial(?) deposits; sand is fine to
medium; unit is grayish-orange to light tan; forms the bulk of a northwest-
trending bar in northeast corner of map

Unit A (upper Pleistocene)

Silt, sand, and gravel—Lacustrine deposits, tan to gray, calcareous, well
bedded, moderately well indurated; some zones of tan, calcite-cemented sand;
ostracodes locally; unit restricted to area south of highway

Tufa, undivided (upper Pleistocene)—Lacustrine deposits; nodose and lithoid tufa

Older gravel (middle to lower Pleistocene or Pliocene)—Alluvial gravels; light- to
dark-brown, reddish-gray, or gray, cobble- to boulder-size fragments in finer
matrix (larger clasts are not well rounded), local well-developed calcareous soil

Bedrock (pre-Tertiary)—Undifferentiated bedrock, mostly plutonic types, some
dikes

oc
2

Contact—Certain

+—+—+—+ Crest of lacustrine bar

10> Strike and dip of beds

Smith, G.l., 2009, Late Cenozoic Geology and Lacustrine History of Searles
Valley, Inyo and San Bernardino Counties, California: U.S. Geological Survey
Professional Paper 1727 [http:/pubs.usgs.gov/pp/1727|

35°41"

35°40"