Description of the Raritan Quadrangle

DESCRIPTION OF THE RARITAN QUADRANGLE. By W. S. Bayley, H. B. Kiimmel, and B. D. Salisbury.« INTRODUCTION. of the province lose much of their definite character, but the Piedmont Plateau and the Appalachian Mountain belt are not Appalachian Valley is continued in the Champlain Valley of separated by a sharp geologic boundary, and in many places GENERAL RELATIONS. western Vermont. geologic formations extend continuously from the mountain Position and area. The Raritan quadrangle lies between In New Jersey the eastern part of the belt is occupied by the belt into the great valley. In the general region including parallels 40° 30' and 41° and meridians 74° 30' and 75° and broad Kittatinny Valley and the western part by the narrow northern New Jersey, southeastern New York, and eastern comprises four smaller (15') quadrangles the Hackettstown, Delaware Valley, the two being separated by the bold even- Pennsylvania, however, the conditions are somewhat different. Lake Hopatcong, High Bridge, and Somerville covering an crested ridge of Kittatinny Mountain, which, although one of Each of the physiographic subdivisions is strikingly different area of 905.27 square miles. It is in northern New Jersey the minor ridges in the Appalachian Valley belt, reaches a from the others in geologic character, although even here (see fig. 1) and includes parts of Hunterdon, Middlesex, Morris, greater altitude than the Highlands east of the valley. absolute lines can not be drawn, as some formations are com Somerset, Sussex, and Warren counties and contains the cities The Appalachian Valley is bounded on the east by the mon to all three. of Somerville, Dover, Washington, and Hackettstown. It is Appalachian Mountains, which in the middle Atlantic States Highlands belt. The Highlands of southeastern New York, named from Raritan River, the chief stream within its borders. form a rather narrow belt of irregular, more or less interrupted northern New Jersey, and eastern Pennsylvania are formed ridges, nowhere of great altitude but as a rule rising rather chiefly of highly metamorphosed rocks of pre-Cambrian age, abruptly from the lower country on either side. South of the which occupy a roughly hook-shaped area extending north Potomac the belt is broader, in western North Carolina reaching eastward from the Reading Hills in Pennsylvania to southern a width of 60 miles and culminating in the highest summits of Dutchess County in New York, thence recurving southward to the eastern United States. In the southern Appalachians the Manhattan Island. The rocks consist of gneisses and schists, rather sinuous divide between the streams flowing to the Ohio possibly in part of sedimentary origin, with some marble or and those flowing directly to the Atlantic is called the Blue crystallized limestone, and of intrusive igneous rocks, also Ridge. For much of its length the Blue Ridge defines the gneissoid for the most part. They have been greatly deformed, eastern limit of the Appalachian Mountain belt and forms a probably more than once, and are now complexly folded and bold scarp facing southeast, toward the Piedmont Plateau. faulted. Infolded with the pre-Cambrian crystalline rocks, In New Jersey the Appalachian Mountains form a belt from and for the most part occupying the narrow valleys which 10 to 25 miles wide, known as the Highlands, which crosses separate the ridges of the Highlands, are strips of more or less the northern part of the State southeast of the Kittatinny metamorphosed Paleozoic strata. The folds have the general Valley. The Highlands consist of several broad, rounded or northeast-southwest trend characteristic of the Appalachians flat-topped ridges, rising 400 to 600 feet above the lowlands on and are roughly parallel to the trend of the Highlands as a either side and separated by deep and generally narrow valleys. whole. The foliation planes of the gneiss dip southeastward Near the Delaware the Highlands are lower and are broken by generally but not universally. 39 broad interhighland valleys. They continue southwestward Kittatinny Valley. Throughout its length the Appalachian into Pennsylvania for a few miles as low irregular ridges. Valley is underlain by early Paleozoic strata, chiefly of Cam 74" They extend northeastward into New York to and across the brian and Ordovician age. The minor valleys are floored with FIGURE 1. Index map of New Jersey and portions of adjacent States. Hudson, beyond which they lose their distinctive character. less resistant rocks, such as limestone and soft shale, and the The location of the Raritan quadrangle (No. 191) is shown by the darker ruling. Published folios The easternmost division of the Appalachian province, lying minor ridges are formed of sandstone, hard shale, and less describing other quadrangles, indicated by lighter ruling, are the following: Nos. 70, Washing ton ; 83, New York City; 137, Dover; 152, Patuxent; 157, Passaic; 161, Franklin Furnace ; east and southeast of the mountain belt, is the Piedmont soluble limestone. In the northern New Jersey region the 162, Philadelphia; 167, Trenton; 182, Ohoptank. Plateau. From New York southward it is bounded on the Kittatinny Valley is occupied chiefly by limestone and shale of Geologic provinces. The Atlantic slope of the United States east by the Coastal Plain. Its surface is that of a dissected Cambrian and Ordovician age, Kittatinny Mountain is formed is included in two geologic provinces the Coastal Plain, which plateau, which slopes gently eastward or southeastward from by resistant sandstone and conglomerate of Silurian age, and borders the Atlantic from Massachusetts Bay southward, and the base of the Appalachian Mountains and is broken here and the Delaware Valley is occupied by shale and limestone of early the Appalachian province, which extends from the Coastal Plain there by knobs or ridges that rise several hundred feet above Devonian age. The strata, which are of the same age as those westward to the Mississippi lowland and from central Alabama its surface. In the southern Appalachian region, where it lies infolded with the pre-Cambrian rocks of the Highlands, have northeastward into Canada. The line separating the two prov well inland, the Piedmont Plateau stands at a considerable been considerably folded and faulted but little or not at all meta inces runs obliquely across New Jersey from a point near Perth altitude, but toward the northeast it is lower, and in the vicin morphosed. The folds and faults here, as in the Highlands area, Amboy to Trenton. Each province is a fairly distinct geologic ity of New York City it falls to sea level. have a general northeast-southwest trend. The oldest rocks are and physiographic unit, whose general geologic history, as In New Jersey the Piedmont Plateau displays few of the exposed along the eastern side of the valley at the western base recorded in its rocks, geologic structure, and physiographic characters of a plateau. It is chiefly a* lowland of gently of the Highlands. Northwesterly dips predominate. development, is nearly the same throughout each part of the rounded hills separated by wide valleys, with some ridges and Piedmont Plateau. The rocks of different parts of the province. The provinces differ, however, in their rocks and isolated hills rising conspicuously above the general surface, Piedmont Plateau differ widely in age. Southwest of the geologic structure and hence have had dissimilar histories. In which slopes gently from about 400 feet above sea level at its Delaware the Piedmont is occupied largely by metamorphic its general geographic and geologic relations the Raritan quad northwestern margin to about 100 feet along its southeastern igneous and sedimentary rocks, similar in most respects to rangle is part of the Appalachian province, but its southeast border near the Delaware and to sea level at New York Bay. many of those of the Appalachian Mountains, but it includes corner is close to the inner margin of the Coastal Plain and, Coastal Plain. All of New Jersey southeast of a line from several large areas of Triassic rocks, a few smaller areas of indeed, contains a few remnants of deposits that are peculiar Trenton to a point near Perth Amboy is part of the Coastal highly metamorphosed Paleozoic strata, and a great abundance to the Coastal Plain province. Plain. Its surface is in general a dissected plain that rises of intrusive granite. Similarly, east of the Hudson the region gradually from sea level at the coast to about 300 feet in GENERAL GEOGRAPHY AND GEOLOGY OF NORTHERN NEW that corresponds geographically and geologically to the Pied JERSEY. central New Jersey. At its inner margin, along the boundary mont Plateau and that may be considered its northeastern between it and the Piedmont Plateau, it includes a broad, extension is occupied chiefly by igneous and metamorphic TOPOGKAPHY. shallow depression lying less than 100 feet above sea level and rocks of pre-Cambrian and Paleozoic age, with included areas Appalachian province. The Appalachian province comprises extending from Raritan Bay to the Delaware at Trenton. of Triassic rocks and others of highly metamorphosed sedi several major divisions, three of which the Appalachian Val The surface of the Coastal Plain extends eastward with the ments regarded by some geologists as Paleozoic and by others ley, the Appalachian Mountains, and the Piedmont Plateau same gentle slope beneath the water of the Atlantic for about as pre-Cambrian. In northern New Jersey, however, the enter New Jersey. 100 miles, where, at a depth of approximately 100 fathoms, it Piedmont Plateau is underlain almost wholly by Triassic strata The Appalachian Valley, the central division of the province, is bounded by a steep escarpment, along which the ocean and associated volcanic rocks. Near Trenton a small area of is a broad belt of valleys and subordinate ridges lying between bottom slopes abruptly to abysmal depths.

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