Description of the Geology of
Lawrence County
Pennsylvania

 
Lawrence. - Area, 370 square miles; population in 1880, 33,312. The Shenango river flowing south out of Mercer county, and receiving Neshannock creek from the north-east at Newcastle, meets (2 miles further south) the Mahoning river from the State of Ohio, and becomes the Beaver river. Along the eastern edge of the county Slippery Rock creek flows S.S.W. and joins the Conneconessing three miles from where the latter enters the Beaver at the county line. All these main valleys are deeply trenched through the Lower Productive coal measures into the Conglomerate (XII), whose solid, massive sandstone upper and middle divisions (Homewood SS. And Coneconnessing SS.) shut the valleys in with vertical cliffs of singularly picturesque beauty. The exceedingly gentle rise of the rocks north-westward brings up the underlying "Sharon shales" in the valley of the Beaver one mile below the mouth of the Mahoning. From this point up the Mahoning and the Shenango, and for two miles up the Neshannock, these shales occupy the lower slopes of all the valleys and ravines, gradually pushing back the Conglomerate series (300` thick) into the hills, leaving only the high lands and divides occupied by the lowest (Clarion) coal series, crowned in three places with Ferriferous limestone, viz: one patch (2 miles long) in Wilmington township; another (3 ½ by 1 ½ miles) in Neshannock township; and a third (3 by 1) in Union township. All the upland east of the Neshannock and east and west of the Beaver river is occupied by the Ferriferous limestone supporting the three Kittanning coal beds; and in Big Beaver and Perry townships the high divides hold also the two Freeport coal beds, and even some of the lowest Barren measures. The Mahoning sandstone is quite shaly in Lawrence county; but the coarse, massive "Buffalo sandstone" (30`) caps the highest ridges of Perry township with bluffs and gigantic blocks. Under it is the Brush creek coal 4`, with underclay 3`, and limestone sometimes 8` thick. The Freeport upper coal (70` lower) locally known as the "Five-foot" and "Four-foot" bed, is over 6` thick in several mines near the north line of Little Beaver Township, but thinner and poorer elsewhere; its underlying limestone seems wanting. The underlying sandstone which makes such noble cliffs on the Ohio river and Little Beaver creek is a laminated sandy shale along the Newcastle and Darlington railroad, but is quarried for flagstones near the west line of North Beaver township, and also south-west of Mt. Jackson. The Darlington (Kittanning) coal bed varies from 2` to 4`, and is exceptionally pure at the Beaver valley mines, being greatly esteemed at iron mills and as coal gas; but in the Slippery Rock valley it gets sulphury. In the S.W. corner of Plain grove township it is "block coal" (4`) and was used raw in the old furnace on Taylor’s run. The most northern outlier of it is on a high knob on the Mercer county line in Washington Township. Eight analyses show from 39 to 41 p.c. of volatile matter, 1.6 to 5.0 ash, 1.6 to 3.0 water, and .5 to 2.5 sulphur. (See Report Q², p.34.) Two other coal beds of the Kittanning series spread through the county and are locally mined, one of which overlies the famous fire-clay deposit of Beaver county, 10` thick where mines 1 mile below Clinton, just outside the south Lawrence county line, and 10` thick where mined by Mr. Henderson north of Croton. Many more miles might be opened on this fire-clay. The underlying 30` Kittanning sandstone is very massive near Harlansburg, and over the ore diggings near the north Wayne line. The "Buhrstone iron ore" seems confined to Wayne, Shenango, Slippery Rock, Scott, and Plain Grove townships east of the Beaver River. At Houk’s mine the section is soft "keel" ore 1`, hard massive mottled ore 7`, bunch and lump ore mixed with buhrstone flint nuggets 6`, lying on the Ferriferous limestone 3`. At some mines there is only from 1` to 4` of ore; at others it swells to 20`, and even (Big bank) to 22`, entirely replacing the limestone in such a way as to show that the deposit was made in an ancient cavern, for a wall of limestone can be seen against which the ore stops. (For eight analyses of this limonite ore see Q<sup>2</sup>, p.42.) The outcrops of the limestone range up and down all the valley sides of the eastern and south-western parts if the county, its usual thickness being 15`, frequently swelling to 25`, or fading away to nothing, and divided into an upper gray and a lower blue limestone (often with an intervening shale) both very fossiliferous: Spirifer cameratus, lineatus, opimus; Productus nebracensis, longispinus, semireticulatus, prattenanus; Hemipronites crassus; Chonetes mesoloba; Euomphalus rugosus; Pleurotomaria grayvilliensis, carbonaria, turbinella; Bellerophon carbonarius, montfortianus, percarinatus, stevensanus; Nucula ventricosa; Nuculana bellistriata; Macrocheilus primigenius, ventricosus; Astartella concentrica; Polyphemopsis peracuta; Aviculopecten carbonarius, whiteii; Athyris subtilita; Solenomya radiata; Macrodon obsoletus; Aviculopinna americana; Nautilus occidentalis; Platyceras tortum; Synocladia biserialis; Lophophyllum proliferum; Orthoceras cribrosum; Archaeocidaris wortheni; Pentremites pyriformis; Zeacrinus mucrospinus, and many others; stems of crinoids sometimes make up one half of the rock; cone-in-cone structure of the rock is common; quarries are numerous, especially near New Castle. Four analyses (Q<sup>2</sup>, p.48) show 93.3 to 95.7 p.c. carbonate of lime, 1.1 to 1.7 carb. Magnesia, .6 to 1.5 oxide of iron and alumina, .08 to .16 sulphur, .017 to .47 phosphorus, 2 to 3 insoluble. Close under the limestone lies the "Scrub grass" or Clarion upper coal of slight importance; 10` to 15` under it the small middle coal (20" thick and quite pure at Crawford’s mine, Neshannock township;) and the lower (Brookville) coal, 2` where mined above East Brook. Between the upper and middle divisions of the conglomerate come the Mercer upper and lower coals, with a limestone over each except where the two beds come together as on Slippery Rock creek. The upper is a "block coal" bed 5` thick a few miles west of Edenburg. Iron ore accompanies the upper limestone. (For the fossils of these limestone see Q<sup>2</sup>, p.61.) Between the middle and lower divisions of the Conglomerate lies a "block coal" bed, which is 2` thick at the falls of Quakertown run. Under the lower division of the conglomerate lies the "Sharon block coal bed," nowhere yet found workable in this county; 40` of shales under this coal are visible at the north and west county lines. Glacial drift covers the whole county north and west of the line of the Terminal moraine (described in Report Z) which crosses the Butler county line and Slippery Rock creek a little below Roseport, the Beaver river at Chewtown, and the Little Beaver where it enters Beaver county. Petroleum (heavy oil) has been got from the Slippery Rock wells in Perry township, about 550` beneath the bottom of the Conglomerate XII; the Lawrence well giving 40,000 barrels up to 1877. 

From: A geological hand atlas of the sixty-seven counties of Pennsylvania :embodying the results of the field work of the survey, from 1874 to 1884. By J. P. Lesley. (Report of progress (Geological Survey of Pennsylvania), v. X ) Harrisburg, PA : Board of commissioners for the second geological survey, 1885.

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