A thin sandstone, 0-5 feet thick, lies below the Campbell Ledge Shale Member at some localities where the base is well exposed. It may be present throughout most of the Northern Anthracite field; but where the Campbell Ledge Shale Member is missing, the sandstone cannot be distinguished from younger Pottsville strata. This sandstone was not recognized in exposures in the Ransom quadrangle.

Lithology.-The Campbell Ledge Shale Member consists of darkgray to black carbonaceous and coaly shale and thin coal lenses. It is massive where fresh but is fissile or platy where slightly weathered. At Campbell Ledge many species of plant fossils, as well as several species of insects, were found in the member (White, I. C., 1883, p. 39-41).

The Sharp Mountain Member is light- to dark-gray medium-bedded to massive very coarse grained sandstone and cobble conglomerate, containing a few lenses of siltstone, carbonaceous shale, and coaly shale. The sandstone is composed of grains of quartz and quartzite, and small amounts of mica, feldspar, garnet, and zircon. The conglomerate is composed of pebbles and cobbles of milky quartz and quartzite as much as 4 inches in diameter and a few pebbles of chert, siltstone, and shale. The lower part of the Sharp Mountain Member contains coarser grained rocks and is generally more conspicuous topographically than the upper part. In mining operations a few thin beds of coal and coaly shale have been found above the Campbell Ledge Shale Member; however, no outcrops of these beds have been found in the quadrangle.

Stratigraphic relations.—In the Ransom quadrangle the Pottsville rests discordantly on the Pocono Formation, as indicated by the thinning of the upper part of the Pocono. The stratigraphic break between the Pocono and the Pottsville is large here, because in other parts of the Northern Anthracite field, as much as 1,000 feet of the Mauch Chunk Formation is present between the Pottsville and Pocono Formations.

POST-POTTSVILLE ROCKS

Name and age.-Rocks of Pennsylvanian age above the Pottsville Formation in the Northern Anthracite field are informally referred to here as post-Pottsville rocks. The formal names for the Pennsylvanian strata above the Pottsville Formation in the bituminous coal fields of western Pennsylvania have not been applied to these rocks in the anthracite region (fig. 6). Correlation of the units of the two regions has been hampered by the dissimilarity of the rocks, the great distance between the regions, and the lack of a precise method for dating the beds. The name Llewellyn Formation has recently been applied to the Middle and Upper Pennsylvanian strata above

the Pottsville Formation in the Southern and Western Middle Anthracite fields (Wood and others, 1962, p. C41-C42).

Paleobotanical dating by C. D. White (1900, p. 830) and correlation by Moore and others (1944, p. 680–681) indicate that the post-Pottsville rocks in this quadrangle may be equivalent to beds near the middle and upper parts of the Middle and Upper Pennsylvanian Allegheny Formation in the central and western parts of the State. A thin limestone near Wilkes-Barre-the Mill Creek Limestone of Ashburner (1886)—that lies about 500 feet stratigraphically above the Marcy coal bed was correlated with the Ames Limestone Member of the Upper Pennsylvanian Conemaugh Formation by I. C. White (1903, p. 259) and by Chow (1951, p. 14). If this correlation is correct, about twothirds of the post-Pottsville strata in the Northern Anthracite field is younger than the Ames Limestone Member.

Distribution and thickness.-More than 2,000 feet of post-Pottsville rocks is preserved in the more deeply folded synclines of the four anthracite fields of eastern Pennsylvania (fig. 1). About 250 feet of post-Pottsville strata is present in the southeastern part of the Ransom quadrangle, but these beds are poorly exposed because they underlie areas of relatively gentle relief that are covered by soil mantle and glacial debris. The more resistant sandstone and conglomeratic beds locally project through the surficial deposits. The positions of the outcrops and exposures of the coal beds (pl. 1) are outlined on land surface by strip pits, subsidence of underground mine workings, and exploration trenches.

Lithology. The post-Pottsville strata in this area consists of interbedded sandstone, conglomerate, shale, siltstone, carbonaceous shale, and five named coal beds (pl. 3). Medium- to coarse-grained thin- to thick-bedded light- to dark-gray quartzose sandstone and fine- to medium-grained medium- to thick-bedded light- to dark-gray quartzpebble conglomerate make up the bulk of the sequence. The sandstone and conglomerate except the coarsest conglomerate are commonly crossbedded. Thin beds of light- to dark-gray shale and light-gray to yellow-brown siltstone are interbedded with the coarser grained rocks. Coaly and carbonaceous shale beds generally lie directly below or directly above the coal beds.

Coal beds. The five named coal beds in the Ransom quadrangle, in ascending order, are the Lower Red Ash, the Middle Red Ash, the Upper Red Ash, the Clark, and the Marcy. The Lower Red Ash coal bed is apparently thin or impure and has been mined only in a few places in the area. The Middle and Upper Red Ash, Marcy, and Clark coal beds have been intensely mined underground and extensively strip mined in the quadrangle. Hill (1888) reported that in

this general area the Upper Red Ash coal bed is more than 8 feet thick. The average thickness of each of the upper four coal beds is about 5 feet. Thin unnamed coal beds are locally present in the map area (pl. 3); however, the authors could not correlate them with coal beds. in other parts of the anthracite field because of the paucity of outcrops and because of the limited mining data available.

Stratigraphic relations.-The contact between the post-Pottsville rocks and the underlying Pottsville Formation is arbitrarily placed at the base of the Lower Red Ash coal bed or at the base of the carbonaceous shale beneath the Lower Red Ash coal bed. This contact corresponds to that used by other geologists (White, C. D., 1900, p. 763; Wood and others, 1956, p. 2678).

QUATERNARY SYSTEM

PLEISTOCENE AND RECENT SERIES

GLACIAL TERRACE DEPOSITS

Scattered glacial terrace deposits of Pleistocene age are present adjacent to the Susquehanna River in the Ransom quadrangle (pl. 1). Terminal glacial deposits of Illinoian and Wisconsin glaciers are present near Berwick, about 20 miles southwest of the Ransom quadrangle. The deposits of Illinoian age reportedly consist of pebbles of black shale and siltstone, gray and red siltstone and sandstone, white sandstone, and quartzite, and a few cobbles of igneous and metamorphic rocks (Peltier, 1949, table 3). Peltier (1949, p. 26) reported that no Illinoian deposits had been found in areas north of the limit. of the Wisconsin terminal deposits in Pennsylvania. The Illinoian deposits that may have been present in the Ransom quadrangle were either removed by the advancing Wisconsin ice sheet or so thoroughly mixed with material carried by the Wisconsin ice that their diagnostic features cannot be recognized. In areas where they can be recognized, Illinoian glacial deposits are distinguishable from younger Wisconsin glacial deposits by their more thoroughly leached condition and by the red and red-brown weathering of the sediments (Peltier, 1949, p. 4).

Glacial terrace deposits in the Ransom quadrangle have been assigned to the Olean Substage of Wisconsin age by Peltier (1949, p. 20). The terrace deposits are present in irregular and isolated patches adjacent to the Susquehanna River. Most deposits occur at an approximate altitude of 720 feet above mean sea level. West of West Falls, well-rounded pebbles and boulders are present at an altitude of about 1,000 feet above mean sea level and apparently constitute the highest terrace deposit preserved in the quadrangle. I. C. White (1883), Itter (1938), Peltier (1949), and others recognized terrace deposits at alti

tudes other than those cited for this area and for adjacent areas to the south, but the deposits are not readily apparent in the quadrangle. Those that are well exposed in the area are not strongly leached or oxidized.

The deposits consist mostly of quartz sand and gravel; 2-5 percent is igneous and metamorphic rock, limestone, and "glomerate." Pink, gray, and green granite and gneiss; white, gray, and pink quartzite; and other igneous and metamorphic rocks occur in these gravels. The sedimentary rocks include "red" and gray siltstones and sandstones, limestones, calcareous "glomerates," and black chert. With the exception of the black chert, the sedimentary rocks could be locally derived from the Catskill Formation. Peltier (1949, p. 18, 20) considered the Mohawk River valley and Adirondack Mountains of New York as the sources of the igneous and metamorphic rocks.

The deposit west of the Susquehanna River near the south edge of the quadrangle and like deposits elsewhere may be more than 100 feet thick.

ALLUVIUM

Alluvial deposits on the flood plain of the Susquehanna River (pl. 1) consist of poorly stratified well-rounded boulders, pebbles, and sand. The boulders and pebbles are not as large as those in the higher terrace deposits; this fact supports the authors' conclusion that the flood-plain deposits were derived partly from glacial terrace deposits. Also, the lower percentage of igneous and metamorphic rocks in the alluvial deposits indicates that these deposits were derived from terraces and from other sources comparatively lacking in igneous and metamorphic rocks.

Crossbedding, ripple marks (probably interference type), and some filled scour channels were observed in alluvial deposits a few miles. south and west of the Ransom quadrangle. Most of these features show that the depositing currents flowed approximately parallel to the direction of flow of the present Susquehanna River. A few crossbeds face the opposite general direction; the course of the depositing stream may, therefore, have meandered.

Much flat-lying and gently sloping area above the flood plain is covered by a mantle of soil containing many rock fragments. The fragments consist of angular to subangular blocks, boulders, and pebbles of siltstone, sandstone, and conglomerate, and subrounded calcareous "glomerate" from the underlying strata. The matrix of this mantle is mostly fine sand but contains some silt and clay. No igneous and metamorphic rocks were found in this mantle; however, the authors believe that it is, at least in part, weathered glacial till.

STRUCTURE

The southeastern part of the mapped area contains the common limb of the Wyoming synclinorium (Wyoming Basin, or Lackawanna Basin, of other reports) of the Northern Anthracite field and the White Deer (Milton?) anticline. The northwestern part of the mapped area contains the gently dipping north limb of the White Deer anticline.

Structure contours on the map (pl. 1) were drawn on the base of the Pottsville Formation but were controlled largely by stratigraphic intervals of the underlying units. Many of the dip-and-strike data used in determining the trend and spacing of these contour lines may not represent the true attitude of beds, because complete elimination of the crossbedding component of dip readings was seldom possible. Furthermore, where the Pottsville has been removed by erosion the attitude of the base, shown by structure contours, is hypothetical and probably different, to some extent, from the attitude before erosion. The dominant structural feature of the quadrangle the White Deer anticline is apparently relatively uncomplicated; thus, the attitude. of the rock in the quadrangle is approximately that shown on plate 1 by the structure contours and by the geologic section.

The White Deer anticline trends about N. 60° E. in the southwest corner of the quadrangle, but its trend changes to about N. 40° E. where the anticline extends past the east edge of the quadrangle. These trends correspond to the strike of rocks in the anthracite field to the southwest and northeast. The White Deer anticline, which plunges about 1° NE. (about 100 ft per mile), is asymmetric. The northwest flank dips about 3° locally, but the dip gradually diminishes away from the crest until it is about 1° in the northwestern part of the quadrangle. The dip of the southeast flank increases southeastward to about 27° in and adjacent to the Pennsylvanian strata. The anticline probably dies out a few miles northeast of the mapped area. To the southwest the anticline may be the Milton anticline. shown by I. C. White (1883, sheet A) on his map of Wyoming, Lackawanna, and Luzerne Counties, Pa.

No faults were found in the mapped area; however three small thrust faults, involving the Catskill, Pocono, and Pottsville Formations, were observed in nearby areas.

ROCKFALL AT BALD MOUNTAIN

A combination rockfall and rockslide involving the upper part of the Catskill Formation has occurred south of Pinnacle Rock along the west side of the crest of Bald Mountain, in the east-central part of the Ransom quadrangle (pl. 1). The resultant rock debris, esti