The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1884-03-20
GEOLOGY IN THE SCHOOLS.
The Great Ice Age and the Drift-Lecture at
the High School by DR.. R, 7. Brown.

to the class in geology at the HiGh-school, taking
for his subject the glacial drift in its geological
and economic significance. DIR. Brown said by
way of introduction that while in human history
the further back we 60 the more mystical does
the record become, the reverse is true of the
geological record. Marion county rests on three
distinct geological members-two Deyonan and
one carboniferous. Over these is deposit of
drift or transported material from fifty to $50
feet thick, which presents problems to the geolo-
gist more difficult than those of the older rocks.
These problems, he said, if ever solved
will be so by the study of the.
great plains of TIE Middle and Western States.
The drift has been heretofore studied by the
wise men of the East, and to great disadvan-
tage, as in New England the glacial agencies
have cut down the hills i'll their course and piled
the eroded materials in promiscuous masses in
the valleys. The eastern drift is, therefore,
local in its origin and deposition, while the
drift in our region is foreign in its character and
general in its deposition. In New England
the drift is, described in the geologies-a pro
miscuous deposit of clay sand, water-worn peb-
bles and powders. All of these are found in
Marion county, but instead of in disorder they
present nearly as much regularity as we find in
the stratifed rocks that underlie the drift, and
the same order is seen throughout the drift
areas of Ohio Indiana and Illinois What We
know of the glacial drift in Marion county is by
the study of the borings from artesian wells,
and examination of the bluffs found on the west
side of White river. These bluffs are from so to
200 feet high. The valley of the White river is
from a mile to four miles wide and the present
river bed is on the west side of it, On the east
side the descent from the table land, which is
the general level of the country to the river is
long, gentle slope The average elevation is l75
feet above the river and 800 feet above tide
water. Besides the artesan wells and the
White river bluffs we can also study the drift
where the glacial action has ploughed out val
| leys of erosion. We have such glacial valley
between Fall creek and White river 1t
is mile wide and seven miles long.
Another glacial valley E, extends from
A third glacial valley lies south of this, mostly
in johnson county, ans between the two is a
narrow ridge of sand and gravel, resting on a
solid basis of blue clay. This ridge has the
local name of Poplar Hill. The margins of these
valleys are we'll defined, being composed mainly
of gravel terraces These are the great natural
cuts or excavations through the glacial drift
which make it easy Of access and study. AT the
base of the drift we invariably find heavy, com
pact, leadcolored clay, which has in it few bowl
ders, and these Of quartzite or trap rocks Over
our county this clay is from twenty to one hun
dred feet thick. This blue clay is sixty feet
thick at IrvingtOn, forty at BrightwOod, twenty
five feet at the University Park well, and eight
feet at the postofhce. Between the blue clay and
the underlying bedrock we almost invariably
find bed, from three to six feet thick, of coarse
gravel or silicious powders. 1t is this coarse
gravel which contains the finest water;iti is always
free from organic matter; it may be always
known by its taste of iron and its tinging
sells red that contain it. We may not know how
this clay came here, but we do know its useful
/ Ia.
broken through, either by wells or natural ifs
sures, it yields pure water, constant in quaint
ty quality and temperature. There are several
noted natural springs of it-One at haywood,
and the Minnewa Springs, at Lawrence The
largest is on the farm of Fielding Beeer two
miles southwest Of the city, where it forms
marsh of several acres, from which large
stream of water flows. These springs are inn
properly known as lphur springs Everything
in contact with these springs has the character
istic iron tinge. The springs about Lawrence
are natural artesian wells. the water rising YER
tically through the blue clay to the surface,
which is one hundred and eighty feet above the
water in White river. In this lower blue clay
fossils. Its source is not agreed upon among
biologists. AT its base are frequently found tho
remains Of a cone bearing forest, probably cy
press or hemloek DR.. Brown said he had found
n cypress log fifteen inches in diameter IN good
state of preservation in the bottom of this clay.
One taken from a well in Fletcher's swamp
and deposited in Butler University. These logs
are not broken or crushed as they would have
been under the march OF a mountain of ice. All
the indications are that this blue clay was de-
posted from quiet water and deep water Its
material is fine, compact and solid If you wish
to see fine exposure of it go to the White river
bank south of the Michigan street bridge 1t is
chemically an aluminous sihcate in a very fine
state of division, and is mechanically mixed with
fine sand of nearly transparent quartz. If you
wash out the clay and pour IL off half the bulk of
it is made of Just such white sand as we have
al h iC Ina to
iron snlphide and when it is baked
the sulphur is driven off and the red oxiGe of
iron formed so that it make red brick. Above
this blue clay is usually found few feet of
coarse sand or fine gravel, making the third dis
tinct layer as you pass up from the bedrock.
The fourth layer is twenty or thirty feet of true
glacial drift, having all the promiscuous charac-
ter of the glacial drift described by Eastern
biologists and text book makers, who are only &C
quainted with this kind of transported material
In and on this true bowlder, or glacial clay, we
have large powders of granite, gneiss and trap
rocks, which are not found in stu nearer to us
than the shores of Lake Superior. Some of
these powders resemble the Quincy granite and
contain upwards of 1000 cubic feet of stone.
In the central and northern part of Marion
county they are almost invariably granite, and
in the southern border of the county usually
gneiss or trap. In this upper drift occur the
gravel terraces which make the best of roads. In
a few places in the county these Lake Superior
powders are SO thick as to interfere with cult
walton. The great mass of this fourth layer is
made up of yellow orange clay. mixed with
sand and enough lime to make the water perco-
lating through it hard.
The terraces of gravel taken with the SECOND
bottoms" bordering White river on one
side or the other, may be regarded as a fifth
member of the transported material covering
our bed rocks These are mound like elevations.
They are from ten te fifty feet high They are
arranged in lines and lie nearly east and sEest-
North Of them is usually level space, and often
swampy lands which DIR. Brown says indicated
the position of mass of ice under which the
water rushed with great force, excavating the
clay below, piling up the heavier sand and
gravel to make the gravel terraces, and CARRYING
the lighter clay and finer sand on to the south,
distributing it over the country until to the
south of us twenty-five or thirty miles, the
bowlder and gravel clay disappears and we arc