THINGS TO SEE
So much of our valley, like much of the ancient east coast of North America, has disappeared as a result of erosion that it’s hard even for geologists to visualize the landscape in and around Turners Falls as it was around 200 million years ago.
But these reddish rocks, called Sugarloaf arkose, document what must have been going on. Alpine-scale mountains to the east were being quickly eroded by monsoon-like storms. Mountain stream waters, containing huge amounts of rocky sediment, poured into our ancient valley. We know this by the streambed features and the large, angular pebbles and small boulders you see in these big red rocks.
THINGS TO KNOW
These rocks come from points west of Turners Falls, mainly from the Greenfield area. The streambed deposits from which these red rocks formed were very thick, over a mile in some places. Mt. Sugarloaf in South Deerfield consists entirely of Sugarloaf arkose.
We call the rocks that formed from these sediments arkosic sand-stones (named for the angular pebbles and coarse sand they contain) and conglomerates (conglomerations, or mixtures, of large but rounded pebbles and cobbles).
These are exactly the materials we expect to see when the sediments from nearby mountains have been aggressively eroded. Mountain stream sediments like these are being deposited today in areas such as Death Valley. We call these deposits alluvial fans.
NEXT STOP
Walk south across the Discovery Center parking lot to 2nd Street. Walk around the block to the corner of 3rd and Canal Streets.
