Thousand Islands – Frontenac Arch is one of four ecoregions of the Mixedwood Plains. The Thousand Islands in the Saint Lawrence River have a distinctive flora and fauna and are a part of the biological corridor. The bedrock is mostly gneiss, granite and marble, more than a billion years old. The Frontenac terrain is the youngest of the Ontario portions of the arch, dated at 1.2 billion years old. These rocks were once part of a large mountain chain of the ancient supercontinent of Rodinia. There is also a meteor crater near Holleford, where the shield meets the limestone plains of southeastern Ontario. The area
Islands in the River Thames reeds, concrete, cement, wood or sheet piling. The islands are listed in order upstream from the sea. In the Oxford area the river splits into several streams across the floodplain, which create numerous islands. On the right bank a large island is created by Seacourt Stream, Botley Stream and Bulstake Stream, and there are smaller islands, including the large mainly built-up island now known as Osney, created by streams between Bulstake Stream and the Thames, including Osney Ditch. The Oxford suburbs of Grandpont and New Hinksey are on an island created by Bulstake Stream, Hinksey Stream and Weirs Mill Stream.