Evolution, Geodynamics, and Morphology of Lenticular Extension Zones of Transform Faults: Comparative Analysis and Kinematic Model

The article presents a new type of morphostructural objects defined by the author: intratransform lenticular extensions confined to active troughs of transform faults. A morphostructural analysis is carried out using geophysical data. It has been revealed that such structures are formed in active zones of transform faults with maximum offset of segments of the mid-ocean ridge. Intratransform lenticular extension zones have been classified, according to which types I‒III of morphostructures were identified, which illustrate not only various evolutionary stages, but also various kinematic scenarios. Type I is a lenticular zone. This type includes small, young (<10 Ma) lenticular extension zones of the local level, occurring mainly in the transform fault of the Southern Hemisphere. Type II is a lenticular transformed basin. It is a lenticular formation at the regional level with a large (~100 to ~300 km) offset formed on a large transform fault with a block of highly deformed lithosphere in the axial part of the lens and shear movements along one of their fringing arc troughs, but without internal spreading segments. Type III is a multitransform lenticular system. This is a global level lenticular formation, located on a large transform boundary with an extreme offset, limited by passive arcuate scarps and enclosed between them by several closely spaced transform fault trough valleys and internal spreading zones. A kinematic model is constructed for identified morphostructure types I‒III in accordance with the classification of intratransform lenticular extension zones.