296 
CEMENT MATERIALS AND INDUSTRY. 
243 
In the Coastal Plain soft limestones of Tertiary age, the so-eallec 
" marls," outcrop at many points. Much of these materials would be 
very satisfactory for Portland cement manufacture. 
Analyses of Tertiary /inns/ones, eastern South Carolina. 
Silica (Si0 2 ) 
Alumina (A1 2 3 ) \\ 
Iron oxide ( Fe 2 3 ) - y 
Lime carbonate (CaC0 3 ) 
Magnesium carbonate (MgC0 3 ) 
12. 90 
7.02 
78.52 
.15 
16.20 
Tr. 
Tr. 
76.88 
1.41 
16. 00 
4.75 
Tr. 
63. 50 
7.00 
18. 60 
.40 
Tr. 
68. 00 
1.20 
10. £< 
1.0 
Tr 
66.0 
2.5- 
1. Strawberry station, Berkeley County. 
2. El wood plantation, Cooper River. 
3. Dixon's plantation. Cooper River. 
4. Goose Creek, 15 miles from Charleston. 
5. Drayton Hall. 
Analysis 1 by Crowell and Peck; analyses 2-5 by C. U. Shepard. 
The analyses given above, while showing well the amount of free 
sand carried by many of these soft Tertiary limestones, hardly repre 
sent their percentages of lime carbonate. Much purer beds than these ( 
are known to occur near Charleston, but no good analyses are availabh 
PORTLAND-CEMENT RESOURCES OF SOUTH DAKOTA. 
PORTLAND-CEMENT MATERIALS. 
The limestone formations of South Dakota which give any promis 
of supporting a Portland-cement industry occur in two different port 
tions of the State. They are thus separated geographically as well a| 
geologically into the two following groups, which will be discussed ir 
the order named: (1) The limestones of the Black Hills district; (2) 
the Niobrara (Cretaceous) chalk of eastern South Dakota. 
LIMESTONES OF THE BLACK HILLS DISTRICT. 
Darton has described the stratigraphy and rocks of the Black Hills 
district a as follows: 
The Black Hills uplift is an irregular dome-shaped anticline, embracing in its morln 
obvious features an oval area 125 miles in length and 60 miles in breadth, with Its' 
larger dimension lying nearly northwest and southeast. It is situated in a wide are* 
of almost horizontal beds underlying the great east-sloping plain that extends tioii 
the Rocky Mountains to the Mississippi River. It has brought above' the genera}* 
surface level an area of pre-Cambrian crystalline rocks about which there is upturned' 
a nearly complete sequence of the Paleozoic and Mesozoic rocks from Cambrian tc 
a Darton, N. H., Twenty-first Ann. Kept. U. S. Geol. Survey, pt. 4, pp. 502 et seq. 
