Generally speaking, I'm not a fan of man-made landscape alteration, but fresh highway roadcuts provide a great unweathered view of the local geology.
A few weeks ago, after years of proposals followed by years of construction, the northern extension of "Super 7" (US route 7) north of Danbury CT finally opened - and the exposures of the Stockbridge Marble along the road are spectacular! The Stockbridge Marble was formed as the rocks of the carbonate bank (limestones deposited off the coast) of ancestral North America were metamorphosed during the Taconic Orogeny ( see blog on 12/2/2009 and the diagram below).
The rocks were further deformed, and actually overtured, in the subsequent Acadian Orogeny. The extent of those deformations are evident in the complex folds pictured here.
Carbonate rocks, including marbles, generally weather faster than silicate rocks, and in SW Connecticut and SE New York many of the regional valleys are underlain by less resistant marbles. Along route 7 between Danbury and New Milford the Stockbridge Marble underlies the Still River valley, and is bounded by harder rocks on either side of the valley. The same rock underlies the Saw Mill River valley in New York where is known as the Inwood Marble (there's a "Marble Avenue" exit on the Saw Mill River Parkway in Pleasantville/Thornwood, and the Shop Rite plaza in Thornwood is built on an old marble quarry there - great outcrops of snowy white "snowflake" marble are still visible on the quarry walls behind the stores, but they're weathering fast!).
Riders of the Hudson Metro North commuter rail can get a good look at the Inwood Marble at the Marbledale stop on the way into Manhattan.
6 comments:
Very cool! How safe is it to pull over and check it out?
In your two pictures, you can see the multiple scales of folding that are very common in deformed carbonates.
Which direction are you looking in the photos?
I parked up on old Rt.7 and walked down alongside the northbound ramp. Very safe, lots of room between guardrail and traffic (nice hand samples at the base of the roadcut, too!)
The manmade outcrop here strikes NE, while the Cameron's Line thrust fault and what looks to me like relict bedding in the marble strikes N, is overturned, and dips steeply to the west (see this map and pamphlet prepared by Greg Walsh at USGS for an authoritative discussion). In the photos, NW is to the right, SE to the left.
I've put the map and the outcrop in a Google Earth file, too.
Hi
This is a great image. Would you mind if i use it in an online rock classification investigation that I am writing for middle school teachers? I would be certain to give you credit for the picture. I am a middle school earth and space science teacher involved in a STEM initiative for education. Please let me know.
Karen Saul
Hi Karen -
I'm pleased that you're interested in using these images - it is an outstanding outcrop that draws the attention of most drivers.
Generally, I'll allow inclusion of my images and content in educational materials that will not be sold for profit or included in any project or collection that might one day be sold or produced for profit. Please email me at steve.kluge@gmail.com and let me know the nature of your project.
This is probably not your area of expertese but, is there fishing allowed at the quarry??
Anon- You're right - out of both my expertise and interest - I have no idea if fishing is allowed there.
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