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Artifacts and Ichnofossils EarthCache

Hidden : 11/21/2009
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Geocache Description:

Here, visitors will explore a rock shelter used by Lenape Indians during the Archaic Period (8,000-1,000 BC), as well as examine approximately 400 million year ago trace fossils, formed by soft-bodied wormlike marine organisms known as Zoophycos.

Location: Bevans, Sandyston Township, Sussex County.

Accessing the trail:

Parking on Thunder Mountain Road at N41 11.681 W74 51.744, near the intersection with Kuhn Road.

Do not go directly from car to cache, but advance to cache via these coordinates for safer and easier access. There is a small, low, camouflaged rock ledge.

Trailhead at N41 11.606 W74 51.689
N41 11.603 and W74 51.668
N41 11.606 and W74 51.653
N41 11.606 and W74 51.649
Arrive at EarthCache site.


Achieves of the New Jersey State Museum, (visit link)

“The Lenape-Delaware Indian Heritage; 10,000 BC to AD 2000”, Herbert C. Kraft, 2001

“Indian Habitations in Sussex County New Jersey”, Bulletin 13, NJGS, 1915

“Caves of New Jersey”, Bulletin 70, NJGS, 1976
Educational Information:

Situated less than 400 yards from the great Indian Trail (Old Mine Road) and adjacent to a tributary of Big Flat Brook, this rock shelter was repeatedly used for short stays over long spans of time, as is evident by the several fireplaces found on site, as well as over the 1,000 artifacts recovered from two archeological digs.

There are other traces at this location of a much older habitation, one that goes back approximately 400 million years. This can be discovered by the study of trace fossils in the rocks creating this shelter. Trace fossils or ichnofossils are not the actual organism but a recording of their biological activity.

The ichnofossil found here is called Zoophycos, believed to have been made by soft-bodied wormlike organism living in marine waters. Zoophycos is the remnants of a “mining operation” that represents the work of this sediment feeder. The trace initiates with an opening at the sea floor that marks a central vertical shaft that connects down to a helical shaped network of burrow traces. When seen in cross section these burrow traces may resemble a herring bone due to the compression from the accumulated weight of subsequently deposited sediment. It is believed that an individual organism did not spend its entire life in a single Zoophycos trace but was responsible for several burrow complexes. These traces correlate to continental shelf water depths during the Devonian Esopus Formation while more recent examples suggest that the critters have migrated down to deeper water depths of the continental slope and deep sea.

To Log this Earthcache:

In order to log this cache, submit a photo from the center section looking into the northern section of the rockshelter. Let us know how many were in your party.

Additionally, please answer this question: are there any inchnofossils on the roof of the rockshelter?

The rock shelter has an overhanging roof projecting up to 20 feet outward, parts of which have become dislodged from the ledge. The rock shelter can be divided into three parts; to the south lies an overhanging rock projecting 8 feet outward, about 10-14 feet above the floor; another overhanging rock projecting 6 feet outward and forming a slightly lower 8 foot high roof forms the central section. A higher degree of enclosure is afforded here due to the two detached blocks, holding up the roof and forming an eastern wall. Finally, the northern section offers the most protection forming a cave-like compartment 16 feet long, 5 feet wide and 6 feet high. All three parts comprise a total 62 ft length and lie in an approximately straight line at the foot of a low cliff.How did the overhang form in the first place? Smaller openings along the rock face both north and south appear associated with an individual joint surface. Joints represent planar fractures in the rock across which there has been no movement. Just to the north is a narrow cave that appears to have formed along a joint. The cave passage has straight vertical walls that represent both sides of a single joint. At its southern end, the tight original joint can be seen. Both sides of the joint separated by as much as 1 meter as witnessed by the current misalignment with the closed joint at the south end of the cave. Movement of one block is geologically recent and could be related to the end of the latest regional glaciation 20,000 years ago.These rocks are part of the early Devonian Esopus Formation of approximately 400 million years ago which continues from upper New York State through New Jersey and across central Pennsylvania. The Esopus consists of siltstone to fine sandstone with minor clay content deposited in a marine basin. This basin resided adjacent to the Acadian Mountains that developed east to northeast of here.

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