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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Intl. Symposium of the Devonian system: Papers, Volume II, 1967
Pages 331-332
Reefs and Carbonates

Devonian Reefs of the Urals

D. V. Nalivkin

Abstract

The Devonian connecting seaway of the Urals was long and narrow. All conditions were favourable for the development of reefs.

Atoll masses were both the biggest of all and the longest living. Their dimensions were: length 4-10 km., width 2-5 km., thickness 400-1600 metres. The development of atolls began in Early Ludlow and ended in Late Eifelian, it lasted for 20-25 m.y. Many atolls had shorter lives, but not less than 10 m.y. They represent basement structures.

Barrier reefs were developed along the eastern shore of the sea. The main feature is a flat, wide surface. On this surface a continental basalt series, including layers of bauxite, rests. Barrier reefs extended along the coast for nearly 200 kms. with a thickness of several hundreds of metres. They had a life of some 10 m.y.

Coastal reefs are rare. Small masses stretch along the eastern and western coasts. Their form is irregularity conical with flat upper surfaces, covered with continental basalts with layers of flint-clays and iron ore. The thickness is about 100 metres. Their life was short, some hundreds of thousands of years. Their age is Ludlow, Devonian and Early Carboniferous.

The most important mineral is bauxite. In some vugs dry bitumen and oil in mineral quality are present. Commercial oil deposits are not yet known.


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