At the top of the upper zone, a claystone sequence about 138 feet thick contains scattered grains and pebbles of quartz and pebbles and boulders of sandstone. Rocks of Early Mississippian age (which constitute the Pocono Formation) locally fill shallow channels in the underlying Catskill Formation, but at most places the contact of the formations appears to be conformable. Coarse sandstone and conglomerate are the predominant rocks of the Griswold Gap Member of the Pocono. The upper part of the Pocono consists of interbedded shale, siltstone, sandstone, and conglomerate. The grayish-brown "red" beds near the top of the formation at localities adjacent to the Ransom quadrangle may be a transition zone between the Pocono and the Mauch Chunk Formation of Late Mississippian and Early Pennsylvanian age.

Strata of Pennsylvanian age unconformably overlie the Pocono Formation in the Ransom quadrangle. These strata consist of coarse sandstone and conglomerate and a few beds of carbonaceous shale in the Pottsville Formation.

A thin bed of carbonaceous shale at or near the base of the Pottsville is here designated as the Campbell Ledge Shale Member. The rest of the Pottsville is assigned to the Sharp Mountain Member. Above the Pottsville are the Pennsylvanian post-Pottsville rocks-a sequence of conglomerate, sandstone, carbonaceous shale, and coal beds.

Deposits of Pleistocene and Recent ages are present as terraces and alluvium along the Susquehanna River. A mantle of soil containing many rock fragments covers much of the gently sloping area above the flood plain. Part of that mantle is probably weathered glacial till.

After deposition of the post-Pottsville rocks, the area was uplifted and gently folded. As a result the dominant structural feature in the quadrangle is the asymmetrical gently northeast-plunging White Deer anticline. Several small faults were found adjacent to the area during this investigation; however, none were observed in the quadrangle.

Twelve wells have been drilled for gas in the quadrangle. Shows of gas below the upper part of the Trimmers Rock Formation were not reported. The gas shows probably were primarily from joints and fractures rather than from porous and permeable strata.

Anthracite has been mined from the five coal beds in the southeastern part of the quadrangle; production was low during 1957-1960.

INTRODUCTION

LOCATION AND EXTENT OF AREA

The Ransom 72-minute quadrangle of east-central Pennsylvania comprises about 56 square miles of Lackawanna, Luzerne, and Wyoming Counties, Pa. It is about 5 miles west of Scranton and 10 miles northeast of Wilkes-Barre, Pa. (fig. 1).

The Ransom quadrangle encompasses no large cities; however, the towns of West Falls, Falls, and Ransom, and several smaller communities, are popular vacation areas along the Susquehanna River. Mill City, in the northwestern part of the quadrangle, and Milwaukee and Austin Heights, in the southeastern part, are business and recreational centers.

The Ransom quadrangle has a good system of paved roads. The northeastern part is traversed by U.S. Highway 6; the southeastern part, by State Highway 92; the east-central part, by State Highway

FIGURE 1.-The Ransom quadrangle (stippled area, upper right) shown relative to the anthracite fields and to the physiographic subdivisions of east-central Pennsylvania.

629; and the west-central part, by State Highway 292. In addition to these highways, many secondary roads in the area are paved. The quadrangle is served by the Lehigh Valley Railroad, whose tracks border the east bank of the Susquehanna River in the quadrangle, and by the Scranton Airport, which is near Schultzville in the northeastern part.

PURPOSE AND SCOPE OF REPORT

This report presents the results of a geologic study of the Ransom quadrangle, which was mapped as a part of the stratigraphic and

structural studies made by the U.S. Geological Survey in and adjacent to the anthracite fields of Pennsylvania. The results of studies made in the Western Middle and Southern Anthracite fields have been published in the Coal Investigation Map and Bulletin series of the U.S.Geological Survey.

Although the bedrock in much of the Ransom quadrangle is poorly exposed, the cliffs along the Susquehanna River provide a readily accessible, well-exposed sequence of rocks of Devonian, Mississippian, and Pennsylvanian age. This sequence overlies the strata of Devonian age which were penetrated by the Transcontinental Production Co. Richards 1 well-the deepest well in the quadrangle. Thus, one of the longest and least structurally complicated rock sections in east-central Pennsylvania can be studied by piecing together data from outcrops and the log of the Richards 1 well. This report accordingly presents the detailed description, stratigraphic interpretation, and geologic setting of this 12,000-foot-thick measured section of Devonian, Mississippian, and Pennsylvanian rocks and thus provides information by which these same rock sequences in more deformed areas can be more easily interpreted.

The report also describes, and includes maps of, the surficial deposits of Pleistocene and Recent age, the topography, and the structure; and it discusses the economic geology of the quadrangle.

FIELDWORK AND EXAMINATION OF WELL CUTTINGS

Most fieldwork for this report was done by the authors during the spring of 1960. The senior author mapped the area underlain by postPottsville rocks in 1957, while preparing a report for the Anthracite Mine Drainage program.

The geology was plotted in the field on aerial photographs at a scale of approximately 1:20,000 or directly on a topographic base map. Data on the aerial photographs were transferred to the topographic base map by use of a universal projector. The stratigraphic sections were measured by use of tape and hand level. Corrections for dip, where necessary, were made in the field.

Samples of cuttings from the Richards 1 well were examined by use of a binocular microscope. A few fragments from each sample were submerged in 6N hydrochloric acid; if a significant part went into solution, the insoluble fraction was then described separately as insoluble residue.

Color terms used throughout the report for the rock descriptions follow the "Rock-Color Chart" (Goddard and others, 1948); lithologic symbols used in the illustrations are those suggested by Maher (1959, pl. 1); and grain sizes were classified according to the grade scale of Wentworth (1922).

ACKNOWLEDGMENTS

The Bureau of Topographic and Geologic Survey of Pennsylvania loaned well cuttings, drillers' logs, and other data on the Richards 1 well, and drillers' logs of other wells in the quadrangle. The authors appreciate the field visit made by Richard R. Conlin of the Bureau of Topographic and Geologic Survey of Pennsylvania and by John E. Johnston and George W. Colton of the U.S. Geological Survey.

PREVIOUS WORK

Of the previous investigations of the geology of the area, the most detailed was reported by I. C. White (1883) as a part of a six-county report in which a measured section along the Susquehanna River in and south of the Ransom quadrangle and other measured sections nearby were described. The Ransom quadrangle was included in statewide or regional studies of the Devonian, Mississippian, and Pennsylvanian rocks by Rogers (1858), Lesley (1892), Willard (1936, 1939), Swartz (1939), and Cleaves (1939). Studies of the Pennsylvanian rocks in the Northern Anthracite field were made by Hill (1887) and Smith (1895).

TOPOGRAPHY AND DRAINAGE

Most of the Ransom quadrangle is in the Allegheny Plateau physiographic province (fig. 1) which is a maturely dissected and glaciated plateau of moderate relief. The southeastern part of the quadrangle is in the Ridge and Valley physiographic province and includes part of the northwest side of the Northern Anthracite field. Land surface in the quadrangle ranges in altitude from 540 feet above mean sea level at the Susquehanna River to 2,280 feet on Bald Mountain at the east edge of the quadrangle. A major part of the land surface lies between 1,000 and 1,400 feet above sea level.

The area is drained by the Susquehanna River, which flows southeastward through the quadrangle in a valley that has retained the gentle meanders of preglacial time but whose walls have locally been oversteepened by glacial action. The flood plain consists of a series of isolated asymmetrical alluvial areas-some as much as 2,000 feet wide that has formed inside the meander loops of the post glacial Susquehanna River.

Tributaries of the Susquehanna locally flow across falls-forming ledges of bedrock in narrow steep-sided valleys; however, in many parts of their courses, the tributaries are still reexcavating their preglacial valleys. Buttermilk and Gardner Creeks are the only perennial tributaries in the quadrangle. The others are intermittent streams that lose their water in the porous alluvium near the Susquehanna River during periods of low streamflow.

The preglacial topography of the Ransom quadrangle was modified by at least two ice advances during the Illinoian and Wisconsin Glaciations (Peltier, 1949, p. 15-16). Because the direction of ice movement differed from the strike of the bedrock by about 40° in much of the quadrangle, glacial erosion truncated or modified preglacial strike ridges to such an extent that in many places the present topography is not indicative of the lithology and competence of the underlying rocks. Ice rounded off many hills and covered them with a layer of ground moraine; it plucked or quarried the well-jointed rock from some hill slopes and locally oversteepened the cliffs along glacial valleys. Valleys transverse to the direction of ice movement were filled with ground moraine, whereas those parallel to the direction of movement

FIGURE 2.-Classification of Devonian, Mississippian, and