IOWA ACADEMY OP SCIENCES. 
195 
designate as the Lower Otis, and the western boundary of the 
Le Claire and Mount Vernon beds, there extends along Big 
creek for ten miles an outcrop of an unfossiliferous, hard, 
heavily-bedded, drab limestone fifty feet in thickness, termed 
the Bertram beds in the author’s report on the Geology of Linn 
county. * 
Supplying, therefore, the upper ninety feet of the well sec- 
tion from the vicinal strata, we have the following succession: 
Number. 
Tliickness in 
feet. 
Depth of low’r 
limit. 
Otis liraestoiie - 
29? 
29? 
Lower Otis limestone 
20? 
49? 
Bertram limestone 
41? 
90? 
17 
(a Chips of dark, slate colored, non-ma«;nesian limestone: argilla 
1 ceous, bard, compact sub-conchoidal fracture, pyritiferous: 
1 showing junction surfaces with green clay. 
I b Smaller chips of light butf magnesian limestone, not porous; lustre 
! earthy. 
L c Green clay 
5? 
95 
16 
Magnesian limestone, or dolomite, light buft. slightly vesicular, lus- 
tre earthy; samples at 95, 105 and 115 feet 
25 
120 
15 
Dolomites, buff, pinkish and grey in color; mostly vesicular, sub- 
crystalline and sub-translucent. Seventeen samples 
324 
444 
14 
Dolomite, hard, grey, argillaceous, with argillaceous powder 
6 
450 
13 
Bluish shale with intercalated limestones at 525, 565 and .595 feet, in all 
seven samples 
270 
720 
12 
Dolomites; rough, hard. Six samples 
65 
785 
11 
Limestones, magnesian, some cherty. Eight samples 
135 
920 
10 
1 
Limestones, briskly effervescent, earthy; in flaky chips, bluish grey 
in color 
15 
935 
930 
9 
Shale and limestone, brown, petroliferous 
15 
.8 
Shale, blue 
40 
990 
7 
Limestone, bluish-grey, in flaky chips; briskly effervescent. Sam- 
ples at 990 and l.UOU’feet 
35 
1025 
6 
Sandstone, of clean white quartz sand; grains rounded and ground. . . 
20 
1045 
5 
Dolomite, grey, cherty; samples at 1,045, 1.080, 1,100 and 1.115 feet 
85 
1130 
4 
Dolomite, arenaceous; in fine buff dolomitic powder with some 
quartzose grains 
40 
55 
1170 
3 
Sandstone, in fine, light yellow quartz sand of angular grains, with 
some dolomite; samples at 1,170, 1.185 and 1,200 feet 
1225 
2 
Dolomite, grey; samples at 1.225, 1,240, 1,260, 1,265, 1,280, 1,290, 1.310, 1,330, 
1,350, 1,560, l,3fi0 and 1,390 feet; at 1,240 and 1,380 feet arenaceous 
175 
1400 
1 
Sandstone, of clean white quartz sand similar to No. 6 but coarser, 
samples at l,40u, 1,420, 1,435 and 1,445 feet; at 1,435 feet slightly 
calciferous 
62 
1462 
*Iow.a Geol. Surv., vol. IV., p. 135. 1895. 
