Tectonic Arch

relatively narrow (several tens of km wide) and long (100-300 km), gently sloping, often asymmetrical uplifts typical of platforms. They usually consist of a system or systems (complex arches) of brachyanticlinal folds (placanticlines) in lenticular or stepped form. The majority of tectonic arches are formed in the boundary zones between anteclises and syneclises or above basement fractures (in connection with movements along them). On younger platforms, tectonic arches not infrequently occur directly over anticlinal areas in the folded basement, reproducing them in a much reduced form. Many small uplifts within a tectonic arch are oil- and gas-bearing. Typical tectonic arches on the Russian plate include the Oka-Tsna, the Viatka, and the Don-Medveditsa tectonic arches.