DESCRIPTION OF THE ACCIDENT AND GRANTSVILLE Prepared under the supervision of William Bullock Clark, cooperating geologist. By G. C. Martin. INTRODUCTION. igneous origin, and at places they include areas drainage lines were established along the present courses of the higher plateau. In Kentucky and Tennessee it of Mesozoic sedimentary and igneous rocks, which of the streams. is preserved over large areas as a nearly featureless LOCATION AND AREA. plain, but in other States it was less perfectly developed, rest unconformably on the much older crystallines. In the southern half of the province the westward- and it has suffered greatly from dissection since it was The Accident and Grantsville quadrangles are flowing streams have their sources on the summit of the ALLEGHENY PLATEAUS. Blue Eidge and flow across the Appalachian Valley as uplifted to its present position. adjacent and are situated for the most part in the well as the Cumberland Plateau. West of this intermediate zone there is a third plain, northwest corner of Maryland. They are bounded Position and boundaries. The Allegheny Pla­ Surface relief. The surface of this division of the which is developed only in the great central basin of by parallels of latitude 39° 30' and 39° 45' and by teaus extend from an indefinite western boundary province is composed, as its name implies, of a number Tennessee and in the western parts of Kentucky and meridians of longitude 79°, 79° 15', and 79° 30'. in the Mississippi and Ohio valleys to a much of plateaus of different altitude and extent. The most Indiana. Each quadrangle covers one-sixteenth of a square more distinct eastern boundary on the Allegheny pronounced of these occupies the southeastern portion of INDUSTRIES AND COMMERCE. degree, or about 230 square miles. Front and its southern extension. The Allegheny the division and extends nearly the whole length of the province. This plateau is very old, and its surface is so The two quadrangles described in this folio are The greater part of these quadrangles lies in Front, which constitutes a distinct escarpment with greatly dissected that its plateau character is not always in an essentially agricultural region, although the Garrett County, Md. A strip about 2 miles wide a steep eastern face, holds a fairly constant linear apparent. It emerges from beneath the Cretaceous cover Georges Creek Valley, which has very important extending across the northern edge of both quad­ position throughout central Pennsylvania. It in central Alabama at a height of 500 feet above sea coal mining interests, forms a small part of the rangles is in Fayette and Somerset counties, Pa., does not, however, continue southward on this line level. From this altitude it ascends to 1700 feet at southeast corner of the Grantsville quadrangle. and another strip two-thirds of a mile wide on the until Maryland is reached, but may be considered as Chattanooga, 2400 feet at Cumberland Gap, 3500 feet at The industries of the remainder of both quad­ western edge of the Accident quadrangle is in dis­ swinging eastward in southeastern Somerset County New Eiver, and probably 4000 feet at its culminating point in central West Virginia. From this point it rangles are restricted to farming and lumbering; pute between Garrett County, Md., and Preston and taking a new position farther east. This line descends to about 2600 feet on the southern line of the latter was formerly of considerable importance, County, W. Va. The southeast corner of the crosses Maryland a few miles east of the Grantsville Pennsylvania and to 2100 or 2200 feet in the central but has become a minor industry by reason of the Grantsville quadrangle lies in Allegany County, quadrangle, thus placing the entire area here under part of the State. Farther north the plateau increases exhaustion of the most valuable timber. Md. The largest towns are Friendsville, Md., and discussion within the Allegheny Plateaus. in width, including most of the northern counties of The best soils are situated on the ancient low­ Accident, Md., in the Accident quadrangle, and The geologic structure, surface features, and Pennsylvania and the southern counties of New York, land surfaces, especially on that now existing as an and ranges in altitude from 2000 to 2400 feet. Elklick, Pa., Grantsville, Md., and Barton, Md., drainage arrangement of the Allegheny Plateaus upland on the areas of Devonian rocks. in the Grantsville quadrangle. have been described by Campbell (Latrobe folio, The character and altitude of this plateau vary greatly in different parts of the province, depending upon the The greater part of the region is lacking in good No. 110) substantially as follows: RELATION TO SURROUNDING REGION. character of the underlying rocks, the general drainage facilities for transportation. The main line of the Geologic structure. The structure of the Allegheny conditions, and the crustal movements which have Baltimore and Ohio Railroad, extends for a short These quadrangles are but a small portion of a Plateaus is comparatively simple. The strata lie nearly affected this region. In its southern part conditions distance along the southern margin of the Grants­ large region the Appalachian Province with flat, and their regularity is broken only by small faults have been very favorable to the preservation of the ville quadrangle, and the Cumberland and Penn­ plateau, and large areas of its even surface are still visible part of which it has much in common. It is con­ and low, broad folds which usually have little effect sylvania Railroad crosses its southeast corner. sequently necessary to note these broader features upon the general features of geology and topography. in Lookout and Sand mountains and in the Cumberland Plateau. North of Tennessee the cap of hard sandstone Branches of the Baltimore and Ohio Railroad in order to grasp the full significance of the more The most pronounced fold is a low, broad arch known as the Cincinnati anticline. The main axis of this fold which protects the Cumberland Plateau is lacking and reach points in the lower parts of the valleys detailed local descriptions which follow. enters the Allegheny Plateaus from the direction of the surface is completely dissected, showing only rounded of Castleman and Youghiogheny rivers. The hilltops as the possible representatives of its once even APPALACHIAN PROVINCE. Chicago, and a minor fold from the western end of Lake National Road crosses the northern part of both Brie joins the major axis near the type locality, Cincin­ surface. In northern West Virginia a few remnants of quadrangles and was formerly an important high­ the original plateau are preserved where conditions are The Appalachian Province consists,of three well- nati. From Cincinnati the anticline passes due south way between the Atlantic coast and the Ohio Val­ to Lexington, Ky., and there curves to the southwest, especially favorable, but generally the surface is so marked physiographic and geologic subdivisions, ley, but since the construction of railways it has parallel with the Appalachian Valley, as far as Nash­ deeply eroded that it is difficult to realize that it was which form parallel belts, each being more or less ville, Tenn. Its maximum development is in the vicinity once approximately flat and extended over most of the fallen into disuse and is now only one of the poorer continuous from north to south throughout the of Lexington, where the Trenton limestone is exposed at Appalachian region. In the northern part of Pennsyl­ of the local highways. greater part of the province. These divisions are the surface at an altitude of 1000 feet above sea level; vania conditions are similar to those prevailing in Ten­ a moderately high plateau region on the west, but in Tennessee it again swells into a domelike struc­ nessee, and areas of considerable size are still preserved TOPOGRAPHY. intact where they are protected by the massive sand­ which includes the Allegheny Plateaus in the ture which is represented topographically by the central DRAINAGE. stones of the Pottsville formation. northern part of the province; a ridge-and-valley basin of Tennessee. This anticline separates the Allegheny Plateaus into Throughout most of the province knobs and ridges The divide between the Ohio and the Potomac region (the "Appalachian valley") in the center; two structural basins, which are best known by the coal rise to a greater height than the old surface of this drainages passes through the Grantsville quad­ and a region of much dissected mountains and low regions that they contain. The western basin extends plateau. Usually these may be distinguished by the rangle. The waters of the Accident quadrangle plateaus on the east. Only the first district is far beyond the limit of the province and contains the fact that they stand above the general level of the sur­ all ultimately flow north and west in Youghio­ rounding hills. represented in these quadrangles. Eastern Interior coal region of Illinois, Indiana, and gheny and Castleman rivers, which join the Ohio. Kentucky. The eastern basin lies entirely within the The plateau slopes westward, but it is generally sepa­ The rocks of the Appalachian Province are in The drainage of the Grantsville quadrangle is large part of Paleozoic age, of sedimentary origin, limits of the Allegheny Plateaus and is generally known rated from the next lower plateau by a more or less as the Appalachian coal region. * * * regular westward-facing escarpment. This feature is equally divided between the Youghiogheny and are fully consolidated, and include both metamor­ Since the Appalachian coal region is a structural basin most pronounced in Tennessee, where it has a height of Castleman tributaries of the Ohio drainage, and phosed and unmetamorphosed types. All the rocks or trough, the strata around its margin generally dip 1000 feet and separates the Cumberland Plateau on the Savage River and Georges Creek, which flow into of the Allegheny Plateaus are of Paleozoic age, toward the center of the field.