NYSGA 1968 C- The Triassic Rocks of the Northern Newark Basin

49 TRIP C: THE TRIASSIC ROCKS OF THE NORTHERN NEWARK BASIN By E Lynn Savage, Brooklyn College of The City University of New York INTRODUCTION Objectives of the Field Trip Outcrops to be visited on this trip have been selected to illustrate some of the problems involved in the interpretation of Triassic rock units and facies in the northern Newark Basin (Figure 1) Where possible emphasis is directed toward general Triassic problems, as well as to those which are unique to the northen1most area of this basin Although it is generally accepted that much of the Triassic has been removed by erosion, there are two contrasting ideas as to whether the present northeastern end of the Newark Basin marks the former extent of the sediments: The present outcrop area is almost the same as the original extent (McLaughlin, 1957, p 1498; Glaeser, 1966, p 101) (1) (2) The sediments were once much more extensive, covering the area between the New Jersey-New York Trough and the Connecticut Trough (Sanders, 1963, 1960; MacLachlan, 1957, p 13; Wheeler, 1938) Nomenc lature Currently there is need for reevaluation of the use of the formational names, Stockton, Lockatong, and Brunswick These units were originally believed to represent a time sequence Subsequently they were found to be 1tinterfingering facies the Stockton in part contemporaneous with the lower portion of the Brunswick The Lockatong is entirely contemporaneous with a part of the Brunswick 1t (Reeside, 1957, p 1459) Attempts to avoid the time significance which had been assumed for the three formations have led to different proposals Reeside (1957, p 1459), Perlmutter (1959, p 7) and Van Houten (1965, pp 832-833) use formation for the three rock units; Glaeser (1966, pp 6-11) uses lithosome for Brunswick and Lockatong, but formation for Stockton; and Savage (1967, p 3) uses lithosome for all three units The most recent evidence, as illustrated on this trip, indicates that in Bergen County, New Jersey, the Lockatong unit interfingers with the Stockton arkose (Figure 2) This reemphasizes the need to eliminate time significance from the names Stockton, Lockatong and Brunswick before alternative designations can be evaluated For example, lithosome, which refers to 1tmasses of essentially uniform lithologic character that interfinger with adjacent masses of different lithologies" (Krumbein and Sloss, 1963, p 301) is applicable, but its use is deferred until the downdip relationships of the units are better und.erstood In the present report the term with priority, formation, is applied to all three units and used properly as a rock stratigraphic unit without time significance BUREAU OF GEOLOGY 'NEW JERSEY a TOP ~# rq-~ TRIP C -, LEGEND TOPOGRAPHY ~U.S -®- ROADS C:> i i STATE ROADS ~., ~ COUNTY ROADS ~~~ GEOLOGY ~ " ~c.J PRECAMBRIAN BASALT , ., ," " .- SCALE MijiiiiII MJJ.NHAffJJ.N TRIASSIC SEDIMENTARY ROCKS FIG NORTHEilN NK'IAlUC BASIN: THIP C, ROU'fE AND LOCATION O}' ~'fOPS " (Tn MILES i HAVE NOT BEEN DIFFERENTIATED 51 Acknowledgements All recent information related to the Lockatong Formation, including stratigraphy, petrology, sections, and interpretation, and Figure 2, is crediL~d to Dr F B Van Houteno He also made a few petrographic studies of the Brunswick rocks in Rockland County, N Y., and pointed out certain aspects of the geolog'y that had not been evident to the writer Much of the information for Rockland County, N Y., including stratigraphy, petrology, sections and interpretation, is from the writerfs Ph D dissertation (Savage, 1967) Special thanks are also due to the writerfs students and those of Dr F B Van Houten who helped with the preliminary field work for this trip Geographic Setting The field trip route is lo~ted in the northernmost part of the Newark Basin and generally delineates a f igure" It starts in the vicinity of Edgewater, Bergen County, New Jersey, at the base of the Palisades, continues to the north across the Rockland County, N Y boundary to Nyack, then turns westerly along the north rim of the Palisades to the western boundary of the Basin, then southwesterly near the foot of the Ramapo Mountains to Suffern, then turns east until the backs lope of the Palisades is reached Here, the route again turns south to the vicinity of North Bergen (Granton) (See Figure 1.) Topography As in other eastern Triassic intermontane basins, the basalts, diabase, sandstones, argillites (Argillite: "an unusually tough mudstone" Van Houten, 1965, p 828), and conglomerates generally form northeast trending rolling hills and ridges At Nyack, however, the Palisades arc into a sickle-shaped ridge trending westward across the basin (see Figure 3) The valleys which commonly are 150-200 feet below the nearby hills, are underlain by rocks composed mostly of clay and silt, called mudstone in this paper (Mudstone: !fa massive aphanitic rock composed of an w1specified mixture of silt and clay Shale - a fissile mudstone " (ibid).) In the area west of the Palisades, thick accumulation of drift covers much of the area, concealing bedrock in the valleys and adding to the problems of correlation Kummel (1897, p 17)reports that the relief under the drift is more rugged than that of the present topography The width of the Palisade Sill outcrop varies, but generally is from less than 1/2 mile to mile wide It is widest at West Nyack where it is miles in width In New Jersey, the ridge has a very even crest, generally devoid of gaps, that becomes higher in elevation northward from sea level at Staten Island to 333 ft at Ft Lee, 433 ft at Englewood, to its maximum height of about 550 ft 1-3/4 miles south of the New York border (Kummel 1897, p 61) In contrast to that crest-line, the Palisades ridge in New York is cut by many gaps, the deepest of which is the 200-foot gap at Sparkill which nearly reaches sea level Four gaps east of Rockland Lake between Nyack oW' ~ '~ '."~'':::': • •• 1"one 40- PtQ ~\.Oc \a.!>e., od,",oc; \.a c;.e., Di.-o\'&· ci e .-:::-, -.:::: - """- ~ -'" -30· " - - j Mil'\.o1'" b\.oti -te o rul c 'nlor·Lte va.f'L-a.b\e Lo c.cU " bon e, be.d ~' C.a.Lc.- !!>',)L