Sand‐box modelling of basement‐controlled transfer zones in extensional domains

Abstract

The interaction modalities of transfer zones connecting rift segments may be influenced by several factors. Amongst these, the location and architecture of transfer zones in narrow rifts has been repeatedly associated with the presence of inherited basement anisotropies. Sand‐box models were made to investigate how the orientation, geometry and kinematics of transfer zones depend upon pre‐existing basement anisotropies. Analogue models reproduced offset rift segments linked by transfer zones bordered by arcuate normal faults. Strike‐slip faults are present inside the transfer zone, provided that angle α (between the extension direction and the axis of the transfer zone) is less than 50°. Narrower transfer zones, striking oblique to the extension direction, occur for angle φ (between the direction perpendicular to the extension direction and the direction of the basement anisotropy) less than 90°; wider transfer zones, subparallel to the extensional direction, occur for φ > 90°. Increasing the overstep induces narrower transfer zones striking subparallel to the extension direction. Similar geometrical and kinematical patterns have been found at transfer zones in narrow rifts. The comparison between experimental and natural data shows how the geometry, kinematics and orientation of natural transfer zones depends upon the trend of inherited anisotropies: transfer zones along inherited basement structures set at lower angles to the extension direction, and display lower aspect ratios, than transfer zones where inherited anisotropies are absent.