Glacial deposits mask the very old rocks of this Till Plain (District 870). At the coast, the reworking of these sediments has created an extensive system of barrier beaches and coastal lagoons. Inland, softer rocks are preserved in the downfaulted Salmon River lowland. Windsor Group rocks are also found on the lowland fringe (District 560) of Bras d'Or Lake abutting the resistant upland known as the East Bay Hills (District 330).