Table 1 (Cont'd).
Focus of paper and
possible indicator type
By Jan 1967, a shifting of water back and forth was effec-
tive in smoothing out 7.6- to 10.2-cm-deep ruts made by a B
52 aircraft the previous September.
Each flood deposited a thin sedimentation unit that in many
places graded from sand and silt near the base to clay near
the top. (These in turned formed mud curls on drying.)
Both playas, which are subject to fairly regular seasonal
flooding, may show a change in basic surface type from one
year to the next. After flooding, a range of surface types
(including a "puffy surface" dissimilar from coarse-grained
puffy surfaces) was transformed into a mud-curl surface.
Rosette patterns were also seen on flooded areas that
underwent freezethaw cycles. Also reported on the north
western part of Rosamond Playa was a "wavy, undulating"
surface with a microrelief ranging from 0.6 to 1.3 cm. It was
broken by irregular "zigzag" polygonal cracks 30.4876.2 cm
Contained water for 18 months (during 1938); maximum pan
Flooded to a depth of 45.7 cm on 21 Sep 1963; completely
evaporated by 20 Jan 1965.
After flooding during the winter of 19651966, the surface,
which was the soft type, became the hard type. By 1967,
some portions of the surface were reverting to the soft type
again (in the absence of flooding).
ment of playas
and dry lakes
The salt-encrusted area of the playa increased at the
expense of other surface types.
Troy and Coyote
Soft, puffy, porous surfaces changing to hard, dry compact
surfaces depending on temporal changes in moisture.
Many playas that have predominantly soft, puffy, porous
surfaces will have hard, dry compact areas in the washes
draining into the playas.
Overview of geo- Southern California
natural history of
many of the southern
Where groundwater or flooding reaches the surface, Dis-
tichlis spicata, Allenrolfea occidentalis, Juncus cooperi
Where the water table is only occasionally at the surface,
the following grow (in addition to above): Sacrobatus
vermiculatus, Salicornia utahensis, and Suaeda torreyana.
la occidentalis, Salicornia subterminalis, Suaeda spp.,
inated by phreatophytic species similar to those report-
and Sarcobatus vermiculatus as representatives of
ed by Hunt (1966) in Death Valley, while the upland
group is dominated by upland species. In contrast to
playa edges. They also report that, farther away from
the playa surface proper, the areas around playas are
the playa edge, other species of xerophytes increase in
often vegetated; sometimes this vegetation can be char-
occurrence until eventually the halophytic shrub zone
acteristic of playa edges. But a gradient does exist be-
is replaced by xerophytes or whatever other commun-
tween the occurrence of halophytic and xerophytic veg-
ity occurs in the region around playas. For Mojave
etation. Barbour and Major (1990) report succulent
Desert playas, Thompson (1929) observed what he
chenopods such as Allenrolfea occidentalis, Nitrophi-
called a characteristic vegetation around the border of