Northern New York is known for its geologic features, that provide astonishing evidence for glaciation, that is - affected by glacial action. Niagara falls, and High and Lower falls of the Genesee are examples of such topography.
The rock layers in Rochester area are virtually undisturbed from their original horizontal position, dipping only slightly to the South. The bedrock in Western New York consists of lower and middle Paleozoic rocks, which are chiefly shales. There are also Late Ordovician through Middle Silurian sandstones, shales, limestones, and dolostones. Repeated transgressions and regressions (sea level rises and falls) are recorded in these rocks.
Now let's talk a bit about these time periods and the rocks formed during them:
The Ordovician Period - about 450 million years ago - is the second period of the Paleozoic Era.
This important period saw the origin and rapid evolution of many new types of invertebrate animals which replaced their Cambrian predecessors. Primitive plants move onto land, until then totally barren. The end of the period is marked by an extinction event.
During the Silurian period, the earth entered a long warm greenhouse phase. However latitudinal variations in climate were rather similar to today, with glaciers occurring in the higher latitudes. Warm shallow seas covered much of the equatorial land masses.
The Genessee River is the only river to completely cross New York State. Its current northward flow has been consistent since the Ice Age. As a result of this, one can see a stratigraphic unit which represents the environments and marine life in which inhabited this area through geologic history.
The rocks seen in the gorge are sedimentary in origin. These sediments represent the depositional environments of the Ordovician, Silurian, and Devonian Periods. On top of this bedrock, lie poorly consolidated rocks and glacial sediments of Pleistocene age. Even though this seems to be a great deal of time, only 2% of the Earth’s geologic history is represented in the gorge.
During the Ordovician, this region was flooded by a shallow inland sea. As a result, a great deal of sand, silt, and carbonate mud were deposited which later became the sandstone, shale, and limestone we see today. Also taking place during this time was the beginning stages of the Taconic Orogeny. As the Taconic Mountains rose in the East, the sediments of erosion came to be deposited in the West, which eventually formed the Queenston Delta. In the gorge, these sediments are seen as the Queenston Formation. This formation is comprised of red shales and siltstones, which contain no fossils. At the base of the lower falls, approximately 55 feet of the Queenstone Formation can be seen. The thickness of this unit reaches close to 1000 feet.
The end of the Taconic Orogeny and the beginning of the Silurian can be seen in the Medina Group. These sandstones are well-known for their oil and gas reservoirs. Directly overlying the Queenston is the Grimsby Sandstone which represents the dying stages of the Taconic Orogeny. The Grimsby is very similar to the Queenston and with both lacking fossils, the contact between the two is uncertain.
The red color seen in these rocks is due to iron oxide resulting from deposition in a highly oxidizing environment.
The Lower and Middle Silurian Age are represented by the Clinton Group. These sediments are mainly shales and thin limestones that represent a quiet time without and mountain building. The aquatic environment represented by the Clinton Group is quite contrasting to the Medina Group. Even though a shallow sea environment still persists, life began to flourish at this time. The Rochester Shale, at the top of the Clinton Group, is quite fossiliferous. The organisms represented here include brachiopods, bryozoans, trilobites and ostracodes. The limestones interbedded with this group formed in clear water where reefs usually flourished. The near complete record of the Clinton Group can be seen in all three falls within the gorge.
Lying above this group
is the Lockport Group. It is comprised of gray, coarse textured massive dolomite. As a result of the dolomite being highly resistant to erosion, it forms the caprock to the falls at Rochester and Niagara Falls. This dolomite layer dips down under the earth's surface around Buffalo, extending westward underground until it reappears west of Chicago--where I live! We have an earthcache in a dolomite canyon which is this same layer of dolomite seen in Rochester. (connecting me to my home town)
The oldest rocks visible in the stream banks, quarries and road cuts in Rochester, N.Y. are upper Ordovician. Approximately 1,000 ft of Queenston shale is the result of extensive erosion of the mountain belt. Queenston includes sandstone, siltstone, shale, and some limestone. It is generally reddish-brown, with some spots of green discolorations, and does not contain any fossils. The lowest visible Silurian unit is the Grimsby (red) sandstone. It is very similar to Queenston. It is a little coarser-grained than Queenston, but was also produced by erosion of late phase of Taconics. The wave ripple marks, burrows and mud cracks identified in this part of Medina sediments are features of shallow sea environment. The upper Grimsby became more off-shore, as the shore line migrated to the East. Grimsby grades into white Kodak sandstone.
Many, many years ago (about 400 million) the area of central New York was covered by a low lagoon called the Silurian Sea. The ore was originally limestone which was replaced by iron compounds from streams high in the Adirondacks that ran to Kirkland. The ore is still found at outcrops and among strata of limestone, shales, and sandstones 60' to 80' underground.
The Clinton hematite formation of ore was first discovered in the Town of Kirkland and named for this place where it was first found in 1797. It is known by geologists throughout the world by the name, Clinton hematite.
The Clinton group of the mid-Silurian is exposed in the gorge North of the Driving Park bridge. The Clinton group 
is heterogeneous (composed of different substances), and consists of marine gray, green and purple shales, interbedded with fossil-rich limestones. It is here we see....
the famous Furnaceville hematite, possibly deposited by iron-precipitating bacteria.
This belt of Clinton hematite goes west throughout New York State and ends in the Province of Ontario west of the Niagara Falls area. It is visible in the Genesee River gorge in Rochester and was mined in an open-trench operation for years by the Furnaceville Iron Company in Ontario County New York. This ore is also found in Wisconsin, Alabama, Virginia, Georgia, Tennessee, and Missouri. It was used in the iron industry at Birmingham, Alabama and at Chattanooga, Tennessee. Similar ores are also located in. Luxembourg and Lorraine in Europe.
Uses of the Ore
Furncaeville hematite was discovered in the Town of Ontario in 1811, providing the basis for an active mining and founding industry that collapsed around 1887 after competition from Pennsylvania and Minnesota. Fine castings for ornamental purposes, stoves, and window weights were the main use of this ore. The iron ore was then mined for use in red paint and mortar coloring into the 1940's.
So, yes TMAACA, that's why so many barns were painted red!
Now, for what you've been looking for--
To get credit for this earthcache, please email me the following:
- Estimate the height in feet from where you are standing to the level of the land above. (think: reference object)
- Measure the width of the Furnaceville Hematite exposed here.
- What kind of fossils would you predict to find in this hematite and why?
- Explain in your own words how this stripe of hematite came to be.
thank you to the following sources of research:
ClintonHistory.org
history.Rochester.edu
Genesee/Finger Lakes Regional Planning Council
St. Lawrence University Geology Club
palaeos.com