“Bedrock of the Newark Basin”

Our region is underlain by reddish sandstones and shales deposited in shallow freshwater lakes

about 200 million years ago during the Triassic- Jurassic Periods.

The solid bedrock beneath our region consists of sandstones and shales deposited about 200 million years ago during the Late Triassic and Early Jurassic Periods. At that time, the ancient continent of Pangaea began to break apart into modern North America and Africa. A series of basins formed along eastern North America from New Brunswick, Canada, to Alabama. The largest of these is the Newark Basin (Fig. 1). This zone extends from Rockland County, NY, across NJ into the area around Gettysburg, PA. Rains eroded the sediments from high peaks to the west, remnants of which are the Ramapo Mountains. Hematite is an iron mineral which cemented quartz and other fragments together and gives these rocks their reddish-brown color.

Evidence of Life in this region during that time indicate the sediments were deposited in shallow, freshwater lakes. Fossilized worm burrows were left when the soft mud hardened into shale (Fig. 2). Many fish fossils and a rare reptile (Fig. 3) were recovered in the Granton Quarry in North Bergen, not far south of Englewood. In Roseland and elsewhere, collectors have found footprints of early dinosaurs (Fig. 4.) The American Museum of Natural History in NYC displays the bones of one of these, Rutiodon manhattenesis (Fig. 5), discovered in 1910 at the base of the Palisades by a geology class from Columbia University.

In what is now the eastern edge of Englewood and vicinity, igneous rocks were forced between layers of these sedimentary rocks during upheavals 200 million years ago as the ancient continent of Pangaea broke up. This formed the Palisades Sill (Fig 6). The “upper contact” between the igneous and sedimentary rocks is exposed in a road cut on Interstate 80/95 just west of the Jones Road Bridge (Fig. 7). The more resistant igneous rocks form the Palisades cliffs along the Hudson River and the sloping surfaces of Englewood’s East Hill section. The less-resistant sandstones and shales form the bedrock beneath Englewood west of Grand Ave. and Engle St.

The solid bedrock in much of Englewood is covered by loose soil materials left by the glaciers during the last Ice Age and the deposits at the bottom of Glacial Lake Hackensack. These explain why people who garden find so many pebbles and other rock fragments.

Two excellent descriptions of the geologic history of Englewood and vicinity are available in:

John K. Lattimer (1990) This Was Early Englewood” Englewood Historical Society. Chapters 1 – 4.

Palisades Interstate Park Commission NJ “Ice, on the Rocks”

Additional general and technical resources are suggested at the end.

Fig. 1. Generalized geology of the Newark Basin

Credit: https://3dparks.wr.usgs.gov/nyc/mesozoic/newarkbasin.htm

Fig. 2 Worm burrows in shale, Flat Rock Brook Nature Center

Fig. 3A. Fossil fish collected in the Granton Quarry, North Bergen – same age as Englewood’s rocks

http://earthphysicsteaching.homestead.com/Triassic_Fossil_Fish.html

Fig. 3B “Tany” (nickname for Tanytrachelos) fossil found in Granton Quarry

http://hudsonreporter.com/view/full_story/7183729/article-NB-fossil-has-NJ-homecoming-Former- resident-remembers-Granton-Quarry-?instance=lead_story_left_column

Fig. 4 Early Triassic Dinosaur Footprints

http://www.digsfossils.com/fossils/pics/Grallator_nj_yale_boonton_0002.jpg

https://en.wikipedia.org/wiki/Riker_Hill_Fossil_SiteFig. 5

Fig. 5. Fossilized bones of Rutiodon manhattenesis discovered in 1910 by a Columbia Geology Class

http://www.naturalhistorymag.com/htmlsite/master.html?http://www.naturalhistorymag.com/htmlsit e/editors_pick/1922_09-10_pick_b.html

Current sign in the American Museum of Natural History

Fig. 6 Cross-section of the Palisades Sill and adjacent sedimentary rocks.

Credit: http://stevekluge.com/geoscience/images/palisades/default.html

Fig. 7 The “Upper Contact” between the Palisades Sill and overlying sedimentary rocks

More information

General

Lattimer, J.K. (1990) This Was Early Englewood. Englewood Historical Society, ch. 1 – 4.

Palisades Interstate Park Commission NJ “Ice, on the Rocks”

“Bedrocks of the Newark Basin--Sediments and Volcanics”

USGS “Geology of the Newark Basin”

Chester A. Reeds “Geology of New York City and Its Vicinity”

Technical

Paul Olsen “Triassic and Jurassic Formations of the Newark Basin”

Paul Olsen “Fossil Great Lakes of the Newark Supergroup in New Jersey”

“Newark Basin and Connecticut River Basin” http://www.digsfossils.com/fossils/footprints_main.html