GEOLOGY OF THE RIDGE AND VALLEY PROVINCE, NORTHWESTERN NEW JERSEY AND EASTERN PENNSYLVANIA JACK B. EPSTEIN U. S. Geological Survey, Reston, Va. 22092 INTRODUCTION The rocks seen in this segment of the field trip range A general transgressive-shelf sequence followed in age from Middle Ordovician to Middle Devonian and characterized mainly by tidal sediments and barrier bars constitute a.deep basin-continental-shallow shelf succes­ (Poxono Island, Bossardville, Decker, Rondout)~ suc­ sion. Within this succession, three lithotectonic units, or ceeded by generally subtidal and bar deposits (Helder­ sequences of rock that were deformed semi­ burg and Oriskany Groups), and then by deeper sub­ independently of each other, have somewhat different tidal deposits (Esopus, . Schoharie. and Buttermilk structural characteristics. Both the Alleghenian and Falls), finally giving way to another deep~water to Taconic orogenies have left their imprint on the rocks. shoaling sequence (Marcellus Shale through the Catskill Wind and water gaps are structurally controlled, thus Formation). Rocks of the Marcellus through Catskill placing doubt upon the hypothesis of regional super­ will not be seen on this trip. position. Wisconsinan deposits and erosion effects are common. We will examine these geologic features as This vertical stratigraphic sequence is complicated a well as some of the economic deposits in the area. bit because most Upper Silurian and Lower Devonian units are much thinner or are absent toward a paleo­ Figure 1 is an index map of the field-trip area, show­ positive area a few tens of miles southwest of the field­ ing the trip route and quadrangle coverage. Figure 2 is a trip area. Thus, the Palmerton Sandstone of Swartz generalized geologic map, (1939) for example, is a probable shallow-marine sand body correlative with parts of the Schoharie and the STRATIGRAPHY AND ENVIRONMENTS Buttermilk Falls. The Palmerton crops out near OF DEPOSITION Bossardsville at Stop 3. The stratigraphic units seen on this trip are more than 15,000 feet (4,570m) thick. Their general characteristics STRUCTURAL GEOLOGY are described in Table 1. More detail is given by Epstein and Epstein (1967, 1969, 1972; Epstein, 1973; and Ep­ The rocks in the field-trip area are disharmonically stein and others, 1967), folded. Four lithotectonic units have been mapped in eastern Pennsylvania (Epstein and Epstein, 1969), three A thick sequence of rhythmically bedded shale (now of which will be seen (fig. 3). The folds in each unit dif­ slate) and graywacke was deposited during Middle and fer, and there is evidence that the units are separated by Late Ordovician basin deepening, forming the Mar­ detachment zones or decoUements, The lithologic varia~ tinsburg Formation which averages about 11,000 feet tions and descriptions of folds are given in Table 2. (3,350m) in thickness, The Martinsburg is divided into Rocks overlying lithotectonic unit 3 are more than three members in this area--a middle graywacke-rich 10,000 feet (3,050 m) thick and are in large folds that member (Ramseyburg) separating two distinct slate­ have wavelengths of several miles (e.g., Weir Mountain dominated members (Bushkill and Pen Argyl). Taconic sync1ineand Lehighton anticline, fig. 2). We will com­ deformation and continental convergence peaked in the pare the characteristics of each of the lithotectonic units Late Ordovician when this area emerged. Uplands to the at Stops 2-4, southeast shed nearly 3,000 feet (915 m) of braided stream deposits (Minsi and Tammany Members of the Two mechanisms produced the folds: 0) flexural Shawangunk Formation), transitional continental­ folding, in which bedding was active and movement was shallow marine sediments (Lizard Creek Member of the either by slip (flexural slip) or flow (flexural flow), and Shawangunk Formation), and meandering stream (2) passive folding, in which movement was along deposits (Bloomsburg Red Beds). laminar flow planes (passive flow) or slip planes (passive 70 ;::! "t1 tri TABLE 1. GENERALIZED DESCRIPTION OF MIDDLE ORDOVICIAN TO r MIDDLE DEVONIAN ROCKS IN THE DELAWARE WATER GAP AREA. '=' ...,Vl c:: a tr1 t---Ta------~----,-~---------------------------------------- Vl u o ..-I 'Tl a Z ::> rrl () ..-I Group, Average ~ s:: Formation, Thickness '-0 ...,o tT1 () or in Feet (m) Description ;;t1 Qj III ..., Member en ~ <!J o m .+.l -rl .c ~ 1-1 +.l • tfl:>.. <!J ..-I o (/) Ul .....:l trl o .1:'"'" Qj o .-l Buttermilk Falls 270(82) Medium-gray cherty limestone, argillaceous limestone, o 'tI i1\ "0 and calcareous argillite. Three members, from base '""!! ~ upward: Foxtown. McMichaels, and Stroudsburg. ;po Z f- '=' o Schoharie Formation 100 (30m) Medium-to-medium dark gray massive calcareous c fossiliferous (including Taonurus) siltstone. 8 tTl --1 Esopus Formation 180(55) Medium-to-dark gray silty shale and s~stone containing o Taonurus. Well developed cleavage 'T1m r '=' ~ Ridgely Sandstone 85(26) Light-to-medium gray fine-to-coarse-grained >-1 t:: ;;t1 <\I and conglomeratic fossiliferous sandstone grading ~p.. til :l Shriver Chert down into medium-dark-gray siliceous calcareous and =a 'M 0 en ,.. J..j and cherty shale and siltstone. 00 Port Ewen Shale 150(46) Medium-dark-gray fossiliferous calcareous shale and 1-1 ~ III siltstone that has well-developed cleavage. H ~ Z o o H :> Minisink l5(5m) Dark-to-medium-gray argillaceous limestone. w Q Limestone Po. :l o New Scotland 75 (23) Medium-to-dark gray cherty fossiliferous shale and C-''"' Formation limestone. Two members. from base upwards: Flatbrookville. Maskenozha. 3 ...00 :l ..c Coeymans 55-HO Medium to dark-gray argillaceous arenaceous cherty Q) -0'"' Formation (17-34) fossiliferous partly biohermal limestone and light­ .-l medium to medium gray calcareous fossiliferous pebbly ~ crossbedded sandstone and quartz pebble conglomerate. Four members. from base" upwards: Depue Limestone. Peters Valley, Shawnee Island, Stormville. a tr1 Rondout Formation 30(9) Light-to-dark-gray calcareous argillaceous fossiliferous o I: r-' <t mud-cracked limestone and medium dark-gray mud-cracked o I-I~~ dolomite: Three members. from base upwards: Dutton­ a I---t :g..., § ville. Whiteport Dolomite. Mashipacong. ~ c..!:::1 0. o 2-!!!..E '"T1 -l Decker Formation 85 (26m) Calcareous quartz-pebble conglomerate, sandstone. and ::r: siltstone. argillaceous and arenaceous fossiliferous tr1 limestone and dolomite. Wallpack Center Member. :::0 8 o m Bossardville 100(30) Medium-to dark-gray poorly fossiliferous mud cracked )­ Limestone argillaceous laminated limestone. Z t1 <: )­ Poxono Island 700~(213) Light olive gray-to-green calcareous dolomitic shale, r 1 Formation dolomite. sandstone. and siltstone. r m '"< "tl Bloomsburg Red Beds 1.500±(l457) Red, green, and gray sandstone. siltstone, and shale ""'III -Co. partly in fining-upw~rd sequences. '"o !:::I p < <tJ ::>1 Z n m Tammany 815(248) Medium-to-medium-dark-gray fine to coarse-grained Member conglomeratic (quartz and argillite pebbles as much as 2 in. lon~crossbedded and planar-bedded quartzite and minor argillite. ~ I-------------~------------~--------------------------------------------------~ Q) ~ .-/ ~ Lizard i75(84) Medium-light-gray to medium-dark-gray and light-olive "=' -0 r2 H Creek Member -rl o gray rippled and flaser-bedded sandstone containing l:: p.. burrows and trails, interbedded with medium-dark-gray .., ~ !:::I to dark-gray burrowed siltstone and shale with rare <tJ § fossils (euryptrids. Dipleurozoa. and Lingula). 00 H ~ III m o~ H m~ :1insi Member 300(91) Light-gray to medium~dark-gray and light-alive-gray I crossbedded and planar-bedded quartzite, conglomeratic quartzite, and quartz, chert. and shale-pebble conglomerate (pebbles as much as 2 in. long) and minor ~ locally mud-cracked argillite. !~~?! -l- ,-----~---~--------------~ ~ Pen Argyl 3,000 - Dark-gray to grayish-black thick-to-thin bedded, evenly 6,000 bedded claystone slate. rhythmically interbedded with ~ (915-1820) ....o quartzose slate or graywacke and carbonaceous slate. ~ ""'III Ramseyburg 2.BOO± P. o""' Medium-to-dark gray claystone slate alternating with ::>P. 1 p.. Member (850) light-to-medium-gray thin-to-thick bedded graywacke 00 z "=' J..I and graywacke siltstone which makes up about 20-30 «: !:::I ::J H <II .0 percent of the member. u Ul Qj !:l rl -r1 "=' .... I~ -0 J..I "r-I Bushkill 4,000+ Dark-to-medium gray thin-bedded claystone slate ~ :il Member (1220) containing thin beds of quartzose siltstone and I~ graywacke siltstone and carbonaceous slate. -J 1 IV 73 FIELD STUDIES OF NEW JERSEY GEOLOGY AND GUIDE TO FIELD TRIPS 75°15' o Contour interval 100 feet ••••••• Field-trip route .......... 3 Field-trip stops Figure 1 Index map of parts of northwestern New Jersey and eastern Pennsylvania showing the field-trip route, stops, and 7-1I2-minute­ quadrangle coverage. slip), and in which bedding was passive and merely Fot many years there has been controversy regarding documented deformation in the movement direction the relative intensities of Taconic and Appalachian (see Donath and Parker, 1964). Flexural slip is indicated (Alleghenian) deformation in eastern Pennsylvania. by bedding-plane slickensides and nearly constant or­ There has also been disagreement on the age and genesis thogonal bedding 'thickness in all parts of the fold, of slaty cleavage, particularly in the Martinsburg Form­ whereas in flexural-flow folding thickness perpendicular ation (see Epstein and Epstein, 1969, p. 163-170, for a to bedding need not be constant. Passive folds are summary). There is