72 
DISTRIBUTION AND MOVEMENTS OF DESERT PLANTS. 
TABLE 2.—Particulars in Physical Structure which may be used to Separate Wash, Playa, and 
Lake Deposits. 




The wash deposits. 
The playa deposits. 
The lake deposits. 

Stratification. 
(1) Stratification 
developed. 
very strongly 
(2) Rapid variations in coarse and 
fine material in both a vertical 
direction and in a direction of 
the strike. 
(3) Bowlders in matrix sand or 
clay. 
(4) Thin layers of flattened, pol- 
ished pebbles overlying dust or 
clay. (Indicates accentuated 
arid conditions.) 
(5) Plunging stratification, small 
pockets of perfectly sorted sand, 
trains of coarse material, varying 
in size up to bowlders 1o feet in 
diameter; all developed in the 
courses of the transient torren- 
tial streams. 
Sizé of material. 
Torrential drainage often has the 
capacity to carry bowlders to to 
20 feet in diameter. 
Distribution of coarse and fine. 
Coarse in the upper edge of the de- 
posits fringing the mountains 
and reaching far down in the 
stream channels, 
The upper limt. 
The upper margin does not lie ina 
horizontal line. It extends up 
the valleys. 
Shape of constituents. 
The bowlders are angular and semi- 
rounded. 
Slope. 
Increase with approach to source, 
farther out very regular. This 
long regular slope is not dupli- 
cated in any other kind of depo- 
sition, 
Other phenomena. 
Wind ripples often developed in 
sandy layers. 

(1) Deposits of mud and 
clay without marked 
stratification. 
(2) Occasional layers of 
single thickness of flat- 
tened pebbles, fitted 
together and polished by 
the wind indicates pro- | 
longed desiccation. 
Very fine sand and clays. 
a) Si teparie 9 © ‘che yore) Wmeiey we Sige fours. 2 ae 
Deposit limited by a 
horizontal line, which 
fluctuates with every 
change in the relation 
of precipitation toevap- 
oration. 
1S Fe. oe wien ew 6) ei he Wel a) a Keen, ove at Sure te Sole 
Practically horizontal. 
Mud cracks, fossil prints, 
etc. 

(1) Stratification marked 
at margin and showing 
less development away 
from shore. 
(2) Typical shore forms 
and stratification due 
to shore action. 
| (3) Deposits sorted to a 
_ uniform size. This is 
never accomplished in 
wash deposits except 
in local pockets in the 
larger stream courses. 
Material larger than cob- 
ble not common. 
At the shore-line. 
Bounded by a horizontal 
line along which may 
develop the erosional 
features of the shore- 
line. 
Bowlders are rounded or 
semi-rounded. 
Decided slope only at 
shore-line and then not 
equaling that of the 
wash. 
Sand dunes can only de- 
velop to any amount 
where there is perfectly 
sorted beach sand to 
furnish the material. 



