Notes on the geology of the Elburz Mountains, north-east of Tehran, Iran

Abstract

Cretaceous outcrops have been traced for the first time in the Lar valley. Two earth-movements are distinguished. The earlier, not previously recognized, is of late Cretaceous, or earliest Tertiary, date; the later, late Miocene. Both are intense. Their periods were separated by great early Tertiary erosion. Effects of the early movement, involving thrusting of Old Red Sandstone over Lias, are well seen near Latiyan and Ab Ali. The direction was probably northwards. Effects of the later movement are beautifully illustrated in steep folding of Oligocene Green Beds, with irregularly directed asymmetry. The Green Beds, 3000 metres thick, are a submarine volcanic accumulation, abounding in radiolaria. Much interest attaches to the Quaternary volcano of Demavend, which grew, like a mushroom overnight, among the eroded mountains of the Elburz. It deflected drainage and led to the production of Lake Lar, now emptied by down-cutting of its spillway.