Look closely:
this boulder contains about six 200-million-year-old balls of mud, now rock, encrusted (“armored”) with pebbles. Jurassic Armored Mud Balls (“JAMBs”) can be easily seen here, but nowhere else in the world!
How many Armored Mud Balls can YOU find in the Jurassic rock above?
More details of the history of the discovery of
JURASSIC ARMORED MUD BALLS:
The unique JURASSIC ARMORED MUD BALLS of the Great Falls Discovery Center
By RICHARD D. LITTLE, Prof. Emeritus Greenfield Community College, May 8, 2025
Rare Jurassic Armored Mud Balls (“JAMBs”) have arrived at the Great Falls Discovery Center (GFDC)! The boulder with 6 mud balls was formerly part of the “Old Red Bridge” suspension cable anchor foundation (now dismantled) on the Turners Falls side of the Connecticut River at Unity Park. In April 2025, this boulder was moved to a special outdoor exhibit spot at the GFDC.
The JAMB rock originally came from a small quarry nearby along Ave. A in downtown Turners Falls circa 1877. Workmen must have noticed these strange, round features set in the sandstone, but they were first “officially” discovered by the author in the early 1970s and were documented in the Journal of Geology (1982). These sedimentary features had never been noted by previous geologists working in the Valley, and, importantly, there are only a handful of other places in the world where they have been discovered, all in remote locations. The JAMBs we have are the only easily seen ones in the world!
Armored mud balls formed when pieces of hard, dry mud fell into a stream. As they tumbled in the current, they became round and coated with pebbles and sand, the “armor”. To be preserved, the newly “sedimentary structures” must be buried quickly in the stream’s sandy gravel sediment. Otherwise, drying would disintegrate the balls. So, 200-million-years-ago, in early Jurassic times, the geologic conditions of Turners Falls (plus Gill, Greenfield, and Deerfield) were just right to form and preserve these unique balls.
The Connecticut Valley has numerous sedimentary rock outcrops with mud chips, chunks, and sometimes balls, but no armored mud balls have ever been discovered. Keep your eyes open! You might discover an armored mud ball in a sedimentary rock layer!
See https:ArmoredMudBalls.rocks for more information, pictures, and a movie. You can also see excellent JAMB specimens along the Geology Path at Greenfield Community College, and there are some JAMBs in the Old Red Bridge’s remaining suspension cable anchor on the Gill side of the river. You have to look carefully to see these.
References and further information:
Little, R. D., 1982, Journal of Geology, 90(2), 203-207.
Little, R. D., 2003, Dinosaurs, Dunes, and Drifting Continents: the geology of the Connecticut River Valley, 3rd ed., 176 p., Earth View LLC.
Little, R.D., 2024, Exploring Franklin County (revised edition), 150 p, Earth View LLC.