The Niagara District sedimentary deposits include:
- sandstone
- shale marine
- limestone
These three types were laid down during the Silurian period 430 – 390 million years ago. Throughout the ages, nature, and a combination of the wind, water, & ice created, has stratified layers of rock and earth in Niagara.
Rock Layers from top layer to bottom layer are:
- Silurian Age
- Clinton Group
- Lockport Limestone
- Decew
- Rochester Shale
- Irondequoit
- Neagha
- Thorold
- Medina Group
- Grimsby
- Power Glen
- Whirlpool
- Ordovician
- Queenston
- Clinton Group
The base of the current Horseshoe Falls is at the lower portion of the Clinton Group of rocks.
The base of the Whirlpool is at the base of the Medina group of rocks. The water level of Lake Ontario is at the rock strata of the Queenston Shale level.
As the water falls reached an area just south of the present Michigan Central Railway Bridge erosion slowed when it encountered the highest limestone ridge in the Niagara District. This limestone ridge extended to just north of present day Eastwood Avenue. The water falls at this point was 15 meters (50 feet) higher than the current water falls. Because of the greater height of the falls the gorge is deeper. At this time Grand Island & Queen Victoria Park was submerged under 30 feet of water.
Precambrian rocks record 80 -85 percent of the Earth’s history. The Phanerozoic Age (the era of well developed life) is recorded in only 15 -20 percent of Earth’s history.