Soils of Saipan^-McCRACKEN 
271 
Primary, climax forests apparently occupied 
the areas of moderate relief which had some 
soil mantle. They appear to have been com- 
posed of such species as daog {Calophyllum 
imphyllum), ifilwood {Intsia hijuga), bread- 
fruit {Artocarpus spp.), several species of 
Pandanus, and others. Soils derived from a 
variety of parent materials were found to 
have no significant differences in organic- 
matter content and carbon- nitrogen ratios 
(Kawamura et al., 1940), indicating no im- 
portant differences in vegetation. 
Areas of steep relief and of rough stony- 
knd in general have a cover of secondary 
tree species, such as Leucaena glauca and Acacia 
confusa, and several species of shrubs. In the 
minor savanna areas, the dominant species is 
"swordgrass” {Miscanthus floridula ?), with 
some Casuarina present. To what extent such 
areas are anthropic (man-caused), was not de- 
termined, but they do occur in areas under- 
laid by both limestone and volcanic rocks. 
PRINCIPAL SOILS AND LAND TYPES AND 
THEIR RELATIONS TO SOILS ELSEWHERE 
Distribution of the principal soils and land 
types is shown in Figure 6. Because of the 
intricate pattern of occurrence of the soil se- 
ries and the small scale of the map, it has been 
necessary to generalize the upland soils both 
cartographically and categorically from the 
original survey. With categorical generaliza- 
tions only a limited number of precise state- 
ments can be made about the classes, or units, 
shown, as the class interval of each is broad 
and includes a wide range of soil conditions. 
The homogeneity of the areas shown is re- 
duced by the cartographic generalization. Soil 
associations or landscapes, rather than dis- 
tinctive soils, are shown. However, the map 
is useful for obtaining a general picture of 
soil distribution on the island. 
Miscellaneous Land Types 
Rough stonyland on limestone includes 
a range of conditions from a few inches (less 
than 4 or 5) of stony soil mantle to bare 
UPPER BAR OF EACH OF THE PAIRS BELOW REPRESENTS PERCENTAGE 
COMPOSITION OF UNALTERED CORE OF BOULDER OF HAGMAN CALCIC 
ANDESITE, LOWER BAR REPRESENTS WEATHERED OUTER MANTLE 
OF SAME BOULDER. (I) 
SiO 
2 
AIzOs 
H 60.95% 
54. 39 % 
18.06 % 
24.03 7o 
FezOs 
FeO 
MgO 
CaO 
NogO 
2.41 % 
■ 5.157« 
■ 2.617® 
0.58 7® 
I 2.37% 
0.58 7® 
■■18.16 % 
0.10 7® 
■ 3.107® 
I 0.44 
CHEMICAL COMPOSITION OF DACITE PORPHYRY IN SANKAKU^AMA 
F0RMAT10N(2) 
SiOg 79 0 % 
AlgOa tm 9.94 7® 
FegOg 11.28 7® 
NagO 13.88% 
11.20 7® 
(1) ANALYSES BY A.C. VLISIDIS, SAMPLES COLLECTED BY R 6. SCHMIDT, 
BOTH OF U.S. GEOLOGICAL SURVEY. 
(2) ANALYSES BY F A. GONYER, DEPT. OF MINERALOGY, HARVARD 
UNIVERSITY, SAMPLE COLLECTED BY R.S. SCHMIDT. 
Fig. 5. Chemical composition of some Saipan vol- 
canic rock. 
limestone outcrops. The modal condition is 
a small amount of mineral soil incorporated 
with loose stones, the soil material extending 
down into cracks and fissures in the limestone. 
The widespread occurrence of this unit (Fig. 
2) is due to the steep topography associated 
with the uplifted limestones. Normal geologic 
erosion keeps pace with soil formation, and 
recurring stages of uplift have accelerated soil 
removal. 
Rough stonyland on dacite describes a 
condition of limited extent in northern Saipan 
(less than 1 square mile) in which practically 
barren dacite or very few inches of gray, acid, 
loamy soil are found overlying the dacite on 
less steep slopes. 
Rough broken land includes those areas 
(Figs. 1, 6) in which weathered rock of vol- 
canic origin is present at or near the surface, 
a zone of organic accumulation being absent 
or very thin. Numerous gullies and erosion 
scars are evident. The weathered, weakly con- 
solidated tuffs and waterlaid sediments from 
volcanic rocks are extremely susceptible to 
erosion, markedly so on steep slopes. 
