Name/Title
Gowanda TilliteEntry/Object ID
2022.2.27.1Description
These Gowanda Tillites can be found in a display case at the Kelleys Island State Park's office.
As written by Mike Angle in 2016, a tillite is a glacial till that has undergone the lithification process and has become a solid rock. The lithification process occurred because of the high pressures associated with burial and tectonics over the years. The Gowganda Tillite or Gowganda Formation represents a particular formation exposed in a west-to-east zone between Sault Ste Marie and Sudbury, Ontario along the northern shores of Lake Huron. This formation is part of a group of rocks known as the Lower Huronian Supergroup and represents some of the oldest sedimentary rocks found in North America. These units, along with surrounding ancient igneous and metamorphic rocks, helped comprise the crustal rocks that formed the core of Laurentia or the North American Craton (Laurentia is a large continental craton that forms the ancient geological core of North America) and other continents ancestral to North America through the eons. The age of the Gowganda Formation has been dated to range roughly from 2.2 to 2.4 billion years ago.
Gowganda Tillites are visually and compositionally are quite distinctive from other erratics. The tillites are quite smooth to the touch and are typically well rounded unless you find one that has been shattered. Tillites tend to be very dense and heavy for their size. They typically have a dark bluish-green or olive-green tint. The clasts or pebbles are variable in color, but pink, orange, and blackish clasts are common. In rare cases, the tillites might look somewhat laminated or layered. Such examples represent glacial lake or lacustrine deposits that were marginal to the ancient ice sheets. In these lacustrine deposits, the clasts represent dropstones. Dropstones occur when a sheet of ice or iceberg floating in a lake melts, and the heavy pebbles or cobbles sink into the lake bottom sediments.
https://ohiodnr.gov/static/documents/geology/OhioGeologyEXTRA_GowgandaTillites_20160824.pdfLocation
* Untyped Location
Kelley's Island State Park
