Ilgenstein Rock is long ridge with good views that extends from Bear Swamp Lake to North Cape on Pierson Ridge. The ridge has an elevation of 1133 feet. The New Jersey Highlands are part of the Reading Prong which is more than a billion years old and formed during Grenville Orogeny. Igneous and metamorphic rocks from the Late Precambrian and Early Paleozoic era make up the highlands. It also contains the Kittatiny and Franklin formations along with Hardyston Quartzite (hard non-foliated rock in white/gray color). Overall the geology is considered complex due to complicated pattern of folds, faults, and intrusions.
During the Pleistocene approximately 18,000 years ago, the region were covered by the Laurentide Ice Sheet. In some places it was up to 1 km thick. It carved out the u-shaped valley and remnants such as striations and chatter marks can still be seen. Chattermarks are series of wedge shaped marks left by chipping of a bedrock surface by rock fragments carried in base of a glacier. They tend to be crescent shaped and oriented at right angles to direction of ice movement.
Logging Requirements:
- While hiking up the mountain (from either direction is fine), does the rock change? Is there any quartz/quartzite visible and how does it compare with the summit?
- From the vantage point (posted coordinates), what evidence of glaciers are visible? Are any striations visible? If so, which direction was the glacier moving?
- Are there any chatter marks in the rock? If so, are they lunate or concentric?
- Upload a photo at Ilgenstein Rock with some of the views. You do not need to be in the photo, though it is strongly recommended.
Special thanks to KanoeBillder for allowing me to use his photo!
Geocache Identification Permit Approval Number: RSP2020071101
Permit Expires on: July 11, 2023