Geology of the New York City Region

44. Riker Hill Park

Riker Hill Park is an excellent location to examine fresh exposures of sedimentary red beds and basalt typical of the Newark Basin region. The park is located along the western side of the Newark Basin near Rosedale, New Jersey, close to the intersection of Interstate 280 with Interstate 287. From Interstate 280 westbound, take Exit 4A and turn south on Eisenhower Parkway. Drive 1.1 miles and turn left onto Beaufort Avenue. After another 0.4 mile turn left onto the entrance road to Riker Hill Park. Drive up hill and park at the Geology Museum. Follow the trail from the museum parking past the ruins of a Nike missile platform, and down hill through the woods to an abandoned aggregate and building stone quarry in the red beds of the Early Jurassic Towaco Formation (Figure 101).

Jurassic Towaco Formation sandstone, Riker Park
Figure 101. Flaggy sandstone of the Jurassic Towaco Formation at Riker Park. The high wall at the upper end of the quarry consists of the Hook Mountain Basalt.

These red bed consist of layered flaggy sandstone and intervening shale that preserve a variety of very well preserved sedimentary structures (mostly ripple marks and desiccation cracks) and occasionally trace fossils (rare dinosaur tracks) (Figure 102). There are numerous small pits where individuals have pried apart layers in search of tracks. A few tracks can still be found on some of the larger, immovable blocks of sandstone that litter the surface. Please don't attempt to remove or modify them!

Fossil mud cracks in Jurassic Towaco Formation, New Jersey
Figure 102. Ancient dried lake muds in the Jurassic Towaco Formation display abundant desiccation cracks and sometimes rare dinosaur tracks at Riker Park, New Jersey.

The Hook Mountain Basalt stands out as the upper high wall of the quarry near the top of the hill (see Figure 101). A thin, light-colored chill zone represents the effect of contact metamorphism in the sedimentary rock along the base of the lava flow. The basalt displays an abundance of vesicles, small vertical holes formed from gases venting from the lava before it cooled. The basalt in the quarry wall also displays poorly-developed columnar jointing. Some of these vesicles and fractures yield the pale green zeolite mineral, prehnite.

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Last modified: 3/11/2019