Page:History of Richland County, Ohio.djvu/183

 HISTORY OF RICHLAND (XJUXTY

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��they probably indicate the bed of an old shal- low swamp, now five or six feet above the pres- ent channel of the adjacent stream. The stratum is from two to three feet in thickness, but not of sufficient extent to be of any great value. Geological Structure. — The geological struct- ure of Richland Count}' is easily- read, and has little variet3\ No single exposure discloses all the rocks of the series, and as the dip is often quite considerable, and is without uni- formity, the measurements of the different strata are only approximations. The subjoined section is the result of many observations and measurements, and will illustrate the general character of the geological structure:

Carboniferous conglomerate 8 to 20 feet

Argillaceous and siliceous shales 170 to "ioO feet

Waverly conglomerate 100 to 190 feet

Argillaceous and sandy shales, some- times bituminous 65 feet

Shales with bands of flaggy sandstone... 235 feet

Berea sandstone..

The highest hills in the northeastern parts of the county are capped with the carboniferous conglomerate, which is, in general, quite thin, rarely attaining a thickness of twenty feet. It frequently contains fragments of chert, and a large quantity of iron ore. In many places it is a siliceous iron ore, and would be valuable if there were a local demand for it. This conglom- erate contains, in many places, a great profusion of calamites — lepidodendra, sigillaria, etc.

Below this is a series of shales correspond- ing to the Cuyahoga shales of the northeastern counties, in part argillaceous, with fragments of crinoids and nodules of iron ore ; and, in part, siliceous, containing the ordinary sub-carbon- iferous fossils. The transition is here apparent through which the varied strata composing the Cuyahoga shales pass in going southward into the homogeneous, sandy, olive shales of the Waverly ; and this member of the series is much more siliceous than it is further north. It varies much in thickness, ranging from 110 to

��200 feet, and over. In places, the lower part of it becomes massive, and not distinguishable from the Waverly conglomerate upon which it rests. Nowliere in it were minerals of any economic value observed.

The Waverly conglomerate is the character- istic rock formation of the county, and, from its lithological character in many places, it might readil}' be mistaken for the ordinary carbon- iferous conglomerate, but its horizon can be definitely traced at a varying distance of from one hundred to two liundred and fifty feet be- low the true conglomerate, and upon careful study can everywhere be readily distinguished from it. It is generally more thoroughh- and evenly stratified than the carboniferous con- glomerate, the pebbles are usually smaller ; the orains of sand forming the mass of rock are mostly globular and transparent. When col- ored by iron it is oftener in regular bands or layers, as the result of more perfect stratifica- tion, and pebbles and grains of jasper are more abundant. The distinction between it and the carboniferous conglomerate of this immediate neighborhood is still more marked. The latter is quite coarse, containing large pebbles, some of them but little rounded fragments of fos- siliferous, cherty limestone, and many coal plants, including sigillaria, calamites, lepido- dendra, cordaites, etc. The plants of the Waverly conglomerate are mainly fucoids. The iron in the latter, shown only l^y the colgr of the rock, is magnetic, preventing the use of the compass in the vicinity of its massive out- crops.

In Plymouth Township, about three miles southwest of Plymouth Village, there is a quarry in the Berea grit, showing something of a transition lietween this quarry rock and the coarse conglomerate. About twelve feet in thickness of the rock has been exposed, the upi)er layers yellow, thin, and much broken ; the lower ones more massive, blue in color and a sandstone grit. The dip of the rock is 5°

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