Transfer zones in extensional basins: their structural style and influence on drainage development and stratigraphy

Abstract

Transfer zones form important structural elements in extensional basins, accommodating displacement changes between individual fault and basin segments. Transfer zone geometry is related to the extension direction and the displacement, dip polarity, overlap and overstep of fault/basin segments adjacent to the zone. Topographic changes associated with transfer zones have a direct influence on drainage basin evolution, sediment transport and stratigraphy. Two main categories of transfer zone can be identified: (i) interbasin transfer zones, linking individual half graben, and (ii) intrabasin transfer zones, linking individual fault segments within a half graben. Interbasin transfer zones range from interbasin ridges to broad faulted highs and major relay ramps. They have a marked influence on basin stratigraphy and drainage evolution, often separating half graben with distinct stratigraphies and acting as conduits through which major axial depositional systems enter the rift zone. Intrabasin transfer zones range from relay ramps separating adjacent en echelon normal faults to discrete fault jogs. Intrabasin transfer zones commonly act as a conduit for local sediment transport, but have minimal effect on basin-scale stratigraphy. Transfer zones also affect early post-rift sedimentation and are important elements in controlling fluid migration in the subsurface.