Rocks of Perry County as to Strcture.
1. Massive Rock. As Granite. 2. Crystalline Rock. As Flint. 3. Stratified Rock. As Sandstone or Shale. 4. Fossiliferous Rock. As Limestone. 5. Sedimentary Rock. As Sandstone. 6. Conglomerate Rock. Pebbles cemented gether. 7. Decomposed Rock. Crumbled. 8. Concretionary Rock. As kidney iron ore. Massive rocks are such as have been produced from within the crust of the earth in a molten condition. Most of them consist of two or more minerals. Their chemical constituents are silica, magnesia, lime, potash, soda, magnetic iron and phospate of lime. Igneous or Eruptive, is another name for massive rocks. The granite found in the drift region, is a repre- sentative of the massive rock in Perry county. Crystalline rocks are those that are formed mainly by chemical deposits. They are frequently found in- terstratified with other kinds. They are being formed constantly by mineral springs, or in the bottom of in- land seas and lakes. The most common Crystalline rock in Perry county is Flint or Chert. Stratified Rocks are such as lie in layers one over the other. Perry county rocks are all classed among the stratified except those brought in by the ice sheet. The strata of the county lie in much the same way as they did when they were deposited on the old sea floor or the bed of the inland sea. They have not been dis- turbed by orogenic agencies and the faults that may be found by borings can be accounted for, in other ways. Fossiliferous Rocks contain fossils. The word11
"fossil" etymologically means "dug up." For many years it included any mineral substance, but its mean- ing is now restricted to include the remains of plants and animals preserved in rocks. Our Fossiliferous Rocks are shales and limestones. Fossils are formed by the decay of animal cells and the mineral constituent taking the place of the organic matter. Our limestones are particularly fertile in fos- sils. They consist of shells of various forms of sub- marine life. Our shales have also an abundance of fossils. The imprint of leaves and stems of trees are especially plentiful. Sometimes the track of a bird is found. Even sandstone contains them in places. They do not occur frequently, however, as there is not suf- ficient plastic material in sandstone to hold the fossil intact. The writer is the possessor of a beautiful fossil in sandrock. It contains four fern leaves. Even the midrib is plainly visible. The fossils found in the coal measures of the county are best known. Many beautiful specimens have been discovered. Impressions of fern leaves, branches and trunks of trees, are of frequent occurrence. They are mostly to be found in the slate over the coal. In the shales that often accompany some of the lighter coal measures of the county may be found excellent fossils of plant life. About a mile east of Junction City the writer found the fossiliferous stem of a plant, fifteen feet in length and was not able to get it all for the road workers had destroyed some of it. The Junction City High School pupils afterward found another one, a part of which they placed in their cabinet of collections. Another Perry county fossil is yet to be mentioned. But it is an alien. It was brought in by the glacial drift. Scat- tered throughout the drift region, especially in the12
northern part of the county, along the terraces of Jon- athan Creek are found numerous remains of coral formations. Some of them are very beautiful, but they are mostly small fragments. Outside of the drift, the Perry county rocks are mostly sedimentary. The limestones were formed by the sittings of organic matter to the bottom of the an- cient ocean. The sandstones, likewise rose from the sea, formed by the small particles of sand that settled from above. The Conglomerates consist of pebbles, cemented to- gether. By silicious matter mixing with them and by pressure, they were crowded into a compact mass. Conglomerates are found in abundance south of Glen- ford at the Old Stone Fort. The geologist Heilprin tells an interesting story of how a friend of his, an old sea captain, had sent him a bolt, that had no doubt come from a wrecked vessel. The bolt having been buried in the sand, the rust from the iron acted as a cement to the small pebbles about it. A sheath of pebbles was thus formed and the bolt could be slipped in and out of its pebbly sheath with ease. This explains the process of making conglom- erates, or "pudding stone" as it is sometimes called. Decomposed Rocks.---All our rocks are to a great- er or less extent decomposed. The process of decom- position is constantly going on. The mechanical action of water, the alternate contraction and expansion of particles of rock, and the work of the frost, are the silent laborers in the disintegration of the rock masses. The presence of iron in a great many of our native rocks is one of the surest methods of decomposition. The oxidation of iron in the sand rocks and shales of Perry county has done as much in tearing down its13
hills after the water had exposed their sides, as any other agency. Some of our rocks were never solid; especially is this true of the shales. They, con- taining little or no sand, had not sufficient weight in themselves to become compact. Containing very little plastic material that could cement them, they are very easily eroded. They are altogether of the nature of decayed wood. In Pleasant, Bearfield and Monroe townships, especially in the latter, we find quite a num- ber of hills that are capped with shale deposits. Some- times we find on ridges, the remnants of these old shale beds standing out by themselves. All has been eroded except a small part which may easily be mis- taken for an artificial earthwork. Concretions are plentiful among the sedimentary rocks. The Concretionary Rocks of Perry county are mostly of the iron ore variety, although concretions of clay and limestone may also be found. These forma- tions were caused by the collection of a mineral around a center. They assume different shapes, usually spher- ical or elliptical. They are dispersed irregularly through other strata. Ferruginous or iron nodules are frequently found in clay. They form quite often about some organic body, such as a fragment of plant, shell or bone. The writer, accompanied by his pupils, on a Geological Field Day, found an excellent specimen of iron nodule; about a mile south of Junction City. In the bed of a stream was found a stratum of pure clay or soapstone, The appearance of a circular rock of a different color, upon the surface of the white stone attracted instant attention. The clay stone being soft, it was an easy matter to remove it from the concretion, for such it proved to be. Upon removal it was found to be some14
six inches long, about two and one-half inches in dia- meter at one end, gradually tapering toward the other The center of it looked like the heart of a tree. The conclusion was that when the clay stone was softer, a branch of wood lodged in it. As the wood decayed, particles of iron, percolating through the soap stone would take the place of the wood cells, until finally the iron had completely substituted itself. It was in real- ity an iron fossil. We were further convinced of the truth of our conclusion by finding a six-inch vein of the purest iron ore in the bank about three feet above the clay stratum. These iron concretions are some- times known as "kidney ore" from their shape. Upon breaking them open, a hollow center is found, usually containing a little clay dust. In these cases the center around which the concretions were made, has decayed, and as they are formed by building layer upon layer from the outside, the original becomes a cavity. The iron nodule referred to above was not formed that way. It built toward the center. The incasement of the wood by the clay prevented the concentric layers from being laid upon it from the outside. The bark of the wood would decay first. Its cells would be filled by the iron. The ferruginous material, always being present, would enter the wood from above. The harder center decayed more slowly and only the finer particles of iron could find lodgment there and conse- quently the branch of the tree was almost perfectly reproduced.15