Latyan Dam (Persian: سد لتيان, also Romanized as Sadd-e Latyān) is a buttress dam on the Jajrood River, located less than 25 km from Tehran in the south of city of Lavasan. It is one of the main sources of water for Tehran metropolitan region. It was constructed between 1963 and 1967. The first generator in the dam's 45 MW hydroelectric power station was commissioned on 17 March 1969, the second on 13 April 1987.
Paleogene period: starts with lower and middle Eocene limestone layers with nummulite fossil and continues with the Alborz green layers. (Green tuffs) which is an indication of submarine volcanic, eruptions and were belongs to upper Eocene.
Quaternary period: The basaltic masses in the alluvial deposits which cover a big area in the region belong to this era.