Vertical Tectonic Movements of the Crust in Transform Fracture
Zones of the Central Atlantic

A. A. Peive

Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia

Received May 23, 2005

Abstract—The most significant vertical movements of the oceanic crust in the Central Atlantic are character-
istic of transverse ridges confined to transform fracture zones. These movements are also recorded in some local
depressions of the Mid-Atlantic Ridge (MAR) and in older structures of deep-sea basins. The amplitude of such
movements substantially exceeds that related to the cooling of lithospheric plates. Vertical movements can be
driven by various factors: the thermal effect of a heated young MAR segment upon a cold plate, thermal stress,
thermal energy released by friction in the course of displacement of fault walls relative to each other, serpenti-
nization of the upper mantle rocks in the transform fault zone, and lateral compression and extension. The alter-
nation of compression and extension that arises because of the nonparallel boundaries of the transform fracture
zone and the unstable configuration of the rift/fracture zone junction was the main factor responsible for the
formation of the transverse ridge in the Romanche Fracture Zone. The most probable cause of the vertical rise
of the southern transverse ridge in the Vema Fracture Zone is the change in the spreading direction. In general,
the fracture zones with active segments more than 100 km long are characterized by extension and compression
oriented perpendicularly to the main displacement and related to slight changes in the spreading configuration.
It is impossible to single out ambiguously the causes of vertical movements in particular structural features. In
most cases, the vertical movements are controlled by several factors, while the main role belongs to the lateral
compressive and tensile stresses that appear owing to changes in the movement of lithospheric blocks in the
course of MAR spreading.

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