Unconformities - ancient surfaces of erosion

An unconformity is an ancient erosion surface - a place where younger stratified rocks have been deposited on older, typically deformed strata.

Traditionally, unconformities are classified into three categories.

DisconformityDisconformity: Middle Ordovician Table Point Formation limestone (grey) on Early Ordovician Aguathuna Formation dolostone (yellow-grey), Aguathuna Quarry, Port au Port Peninsula, Newfoundland, Canada.

angular unconformity

Angular Unconformity: Triassic Wolfville Formation on Carboniferous Horton Group, Whale Cove, Nova Scotia, Canada.

nonconformityNeoproterozoic Torridon Group on Paleoproterozoic Lewisian gneiss, northwest Scotland, UK.