GREEN SCENE

Road trip: Meeting the real fossils of New Jersey

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Ugh! What’s that smell? 

When one thinks about New Jersey, the “Garden State,” the first thought that probably comes to mind environmentally is the odor around Exit 13 on the New Jersey Turnpike. The second thought might be the beautiful Pine Barrens of south Jersey. 

However, most people do not realize that New Jersey has phenomenal dinosaur remains, typically footprints and some skin impressions, remnants of Late Triassic age (around 210 million years ago) wanderings of these creatures along the shores of large fresh water lakes. These lakes existed from around Haverstraw, New York, south to past Reading, Pennsylvania.    

Not only are there dinosaur remains in New Jersey but there is a very diverse fauna of terrestrial (land-dwelling) vertebrates such as gliding reptiles (Icarosaurus), Amphibians (Eupelor), phytosaurs — similar to crocodiles — (Rutiodon), dinosaurs (Eubrontes, Grallator), as well as aquatic tetrapods (four-legged critters) (Tanytrachelos) and fish (Semionotis, Diplurus).

Invertebrates are also very common: clams, ostracodes, insects, crustaceans (branchiopods, crayfish) and trace fossils (a preserved track or footprint but not the body fossils of the critter who made the trace). Plant remains include pollen, spores and roots.  

While I was walking along a shale outcrop looking for fossils on the rock face, I nearly tripped over a slab of shale. When searching for fossils, I am so intent on observing every piece of exposed rock that I don’t really look where I am walking and have come within a foot of stepping on a timber rattlesnake (they are actually very docile when handled gently). 

Of course, I picked up the piece of shale, and amazingly, there was a clear impression of a dinosaur footprint. After returning to my lab, I was able to determine that the footprint belonged to a Grallator. The dino was apparently strolling along the shores of a large lake and made the footprints in damp mud that eventually hardened and were preserved so nicely. 

I was driving along Route 46 heading east, not far from MetLife Stadium where the New York Giants play, when I pulled into an Exxon station at the junction of routes 3 and 46 (south side of the road). As the car was being filled I wandered to the rear of the station to look at an outcrop of what appeared to be shale. 

I immediately realized that an earthquake had occurred here. There was a fault plane cutting across a channel fill, which is an alluvial deposit in a stream channel. Upon further observation, I noticed that the fault was a type referred to as a “normal” fault, where one wall of rock (the higher block, or “hanging wall”) moves down relative to the lower one (“footwall”). 

Faults are caused by movement of blocks of the Earth’s crust due to earthquakes. The fault cut across the channel fill indicating that it occurred after the streambed was filled with sediment. 

After measuring the strike, or compass direction of the fault plane, it became clear that the fault was in conformity. That is to say that it was oriented in the same geographic direction of the famous Ramapo Fault (also known as the Triassic Border Fault) which was caused by subsidence (down-dropping) of a block of about 10,660 meters thick (including igneous bodies — in this case a half-graben) referred to as the Newark Supergroup. 

This major fault separates igneous rock to the west from the large accumulation of sediments to the east. Within the sediments are three lava flows and an igneous body that was intruded between the sediments during the Triassic Period. This structure is commonly known as the Palisades. 

A series of 20 “rift” basins, that is depressions where sediments accumulate, exist in eastern North America along an ancient plate margin. Examples of some of these basins, from south to north, include: Sanford, Durham, Farmville, Richmond, Culpepper, Gettysburg, Newark, Hartford and Fundy basins.   

One interesting (and scary) feature of the Triassic Border Fault is that its geographic axis is pointing directly at the Indian Point Nuclear Power Plant at Buchanan. If there is a strong earthquake and rupture along the fault. there may be some serious consequences (think “The China Syndrome”). 

Another interesting feature of the geometry of the Newark Basin is that it is similar to the Dead Sea Rift model proposed by some geologists. There we have rhomb-shaped down-dropped blocks (grabens) very similar structurally to those along the eastern part of North America.

That’s all for now folks; heading out to the field again looking for the next amazing find in the long sequence of Earth history.

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Lynne Bailey

I'm not sure how I stumbled upon this story. I live in Chicago, but share the writer's wonder of the natural world. What a terrific newspaper to produce this regular column. I also enjoyed the interesting story about the Osage orange. It's great to read about citizen scientists!

| Friday, January 12