Massachusetts

The Jurassic Armored Mud Balls of the Connecticut River Valley

Among the oldest sources of local pride in the Connecticut River Valley are the rare and rarely seen Jurassic Armored Mud Balls.

An armored mud ball consists of a large ball of mud coated with gravel and sand that turned into rock over many, many years. They range from two inches to 20 inches. They start off as chunks of clay broken off from a stream bank and then rolled downstream, collecting the sand and gravel.

Usually they disintegrate, but when buried before they dry they turn into rocks – “lithified” in geologists jargon. Geologists use them to date ancient streams.

A Jurassic armored mud ball embedded in rock.

The ones found in Turners Falls date to the Jurassic period, some 200 million to 145 million years ago.

Geologist Richard Little calls them “interesting, amusing and rare.”

Jurassic Armored Mud Balls

Little, professor emeritus of Greenfield Community College, wants the Commonwealth of Massachusetts to recognize the Jurassic armored mud balls as the official “state sedimentary structure.”

He notes Massachusetts has a state bean (Navy), muffin (corn), donut (Boston Crème)  and cat (Tabby). The Legislature has also elevated other rocks to official status, such as Dighton Rock, a boulder with mysterious writing on it found in the Taunton River. It also has an Official Historical Rock, Plymouth, though the Pilgrims didn’t step on it. Finally, there’s the official Rolling Rock – not the beer, but the one in Fall River that rocks back and forth.

So why not an Official Jurassic Armored Mud Ball?

The Geology Path at Greenfield Community College

Only in Franklin County

They have also been found in other places, including the base of the clay cliffs at Aquinnah on Martha’s Vineyard. Other U.S. locations include Washington, Montana, Wyoming and in a ravine in northeastern Monroe County, Indiana. And outside of the U.S., people have found them in Greenland; Spitzbergen Ecuador, Trinidad, France and Yorkshire, England.

But to date, people can only see them easily in Franklin County, Mass. That’s where Richard Little first laid eyes on them. He noticed them in an old abutment to a bridge that used to connect Gill and Turners Falls, a village in Montague. The stone blocks used in the abutment had been quarried nearby.

The old bridge connecting Turners Falls to Gill

Ironically, the Jurassic armored mudballs in the bridge abutment are only two miles from dinosaur footprints. The Connecticut River Valley has quite a few of them, too, preserved in sedimentary rock.

Little has found eight places where people can see the armored mud balls, all in Franklin County. They include the Geology Path at Greenfield Community College, Unite Park in Turners Falls, the Gill Bridge Cable Anchor and the Stop & Shop in Greenfield.

Here’s Professor Little explaining what they are:

Steve Mabee, the state geologist, recognizes it as “one of the rarest structures in the world…only found here in Massachusetts.”

For more information, https://armoredmudballs.rocks.

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