|VIEW FROM THE MAIN STREET BRIDGE OVER THE ERIE CANAL|
|Samuel J. Ciurca, Jr., Rochester, New York Copyright 2000-2001 Samuel J. Ciurca, Jr. and the
Town of Pittsford, New York
|At the right is the Pittsford Town Hall built in 1890--to many this is a long time ago--to me this is 'yesterday.' Humans have been on our planet for perhaps 100 thousand years to, maybe, 3 million years ago (depending upon what you consider human). Directly beneath the Town Hall are sediments (soil and glacial deposits formed during the last, perhaps, 10 to 25,000 years. Directly below this are very old rocks (BEDROCK) consisting of red and green shales and thin dolostones--part of the Salina Group of Late Silurian age.|
|COMING TO THIS PAGE
A DESCRIPTION OF THE ROCKS BENEATH THE TOWN HALL
"BENEATH OUR FEET." PLEASE VISIT AGAIN!
|410 MILLION YEARS AGO, PITTSFORD, AND MUCH OF WESTERN NEW YORK, WAS QUITE A DIFFERENT PLACE.
|Walking around the Village of Pittsford seemingly reveals little of our geologic past. But if you look at the Erie Canal from the Main Street Bridge, when the waters have been withdrawn for the Winter, you will see rapidly-weathering red shales along the banks of the canal. These shales belong to the Vernon Formation of Late Silurian age (about 410 million years ago). In the subsurface to the south, salt mines intrude these beds to reclaim great quantities of salt (HALITE) mostly in the form of rock salt to be utilized on our area roads. The Retsof Mine, located near Geneseo, New York, is one example.|
|BENEATH OUR FEET
WHAT WOULD WE SEE IF WE DUG A HOLE IN FRONT OF THE TOWN HALL?
|What we would see are several feet of soil underlain by many feet of glacial deposits, including abundant glacial erratics. Bedrock is actually relatively close to the surface, as can be seen near the Main Street Bridge over the Erie Canal (what was formally the Barge Canal). The bedrock consists mostly of a thick sequence (about feet) of shale and mudstone of various colors (reds, greens, black and bluish beds) and thin dolomitic units, some very fine-grained (WATERLIMES) and some not unlike the more grainy dolostone of the underlying Lockport Group. It is, of course, the black shale units that contain the eurypterid faunas described by Clifton E. Sarle and others. At least 3 eurypterid horizons are known within the Pittsford area, and another in the Penfield area. During 1996, excavations along the old Erie Canal revealed a very nice sequence of some of the layers of rock underlying Pittsford, including one of the eurypterid beds (the Pittsford Member of the Vernon Formation, Salina Group). The study of the layers of rock is termed STRATIGRAPHY. Take a look at the sequence observed in 1996 during excavations near the old Erie Canal at Pittsford--CLICK HERE.
The Pittsford Black Shale (shown at left) is currently known only in the Pittsford area. It may correspond to a horizon found at North Chili, where STROMATOLITES are associated with the eurypterid remains found there. However, Hughmilleria socialis has not been observed at North Chili, only E. pittsfordensis. At Penfield, still a different (older?) eurypterid horizon occurs.
|At left, a view of the Barge Canal, now called the "Erie Canal" for commercial purposes. The left bank consists of red and green shale that weathers rapidly back into clays--clays were the source for the formation of the rock in the first place. Upstream, on the left, is the type section of the Barge Canal Member of the Vernon Formation, a black shale similar to the stratigraphically lower Pittsford Black Shale bearing the eurypterid fauna discussed within this website.|
|Construction for a 2-story Wegman's Restaruant at Pittsford Plaza has again revealed very little of the underlying Pittsford Black Shale. The chunk of black shale above was collected August 31, 2001, but very little rock was excavated. Only partial remains of Eurypterus pittsfordensis were observed. Since the new restaurant will not contain a basement, excavations are generally shallow and not likely to pro- duce quantities of the black shale needed to reveal any new features of the fauna.|