Stony Creek Granite Gneiss - Wildwood State Park - January 1, 2009
The Stony Creek Granite Gneiss, which contains a large amount of pink feldspar, occurs in the bedrock of southeastern Connecticut and Long Island Sound. The unit may also be present in the bedrock that underlies Long Island.
It is generally considered to be Proterozoic in age, meaning it formed prior to 543 million years ago.
This boulder was carried from Long Island Sound or southern Connecticut by the Laurentide Ice Sheet that reached its maximum extent on Long Island about 20,750 years ago. In its center is a vein of pegmatite, which contains larger crystals of feldspar and quartz than the surrounding material. The pegmatite is a result of slow cooling of molten material to form solid rock, which allowed the larger crystals time to form.
According to the Master of Science thesis entitled
Analysis of Boulder Distribution: Implications for Glacial Processes in the Vicinity of Wildwood State Park, Wading River, New York (pdf), presented by Jessica Leigh McEachern at Stony Brook University in 2003:
Wildwood State Park on Long Island's north shore features many glacial erratics situated on the beach and throughout the park itself. Most of these boulders have been classified into three distinct lithologies: granite, granite gneiss, and basalt. The majority of granites and granite gneisses are comparable to those found in the Branford-Stony Creek Massif of southeastern Connecticut. The Branford-Stony Creek Massif is part of the Avalonian Terrane, which dips southward from southern Connecticut, underneath Long Island Sound and continuing underneath Long Island.
According to
Wikipedia: Avalonia:
Avalonia was an ancient microcontinent or terrane whose history formed much of the older rocks of Western Europe, Atlantic Canada, and parts of the coastal United States. The name is derived from the Avalon Peninsula in Newfoundland.
From
Wikipedia: Laurentide ice sheet:
The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, between c. 95,000 and c. 20,000 years before the present day. Its southern margin included the modern sites of New York City and Chicago, and then followed quite precisely the present course of the Missouri River up to the northern slopes of the Cypress Hills, beyond which it merged with the Cordilleran Ice Sheet.
Up to two miles thick in Nunavik but much thinner at its edges where nunataks were common in hilly areas, this ice sheet was the primary feature of the North American ice age.
A nunatak is a prominent peak or ridge, surrounded by an ice sheet or glacier, but not covered by ice.
Additional Information on Long Island GeologyUSGS: Quaternary History of the New York BightGoogle Earth Community: Long Island SoundGoogle Earth Community: Classic Map of Long Island Geology as an OverlayGoogle Earth Community: Connecticut Bedrock and Long Island BouldersGarvies Point Museum and Preserve: Geology of Long IslandLong Island Geology by Dr. J. Bret BenningtonField Trip: Pleistocene Geology of Long Island's North ShoreGeologic History of Long Island Sound by Ralph Lewis
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