Evaluating lateral compaction in deepwater fold and thrust belts: How much are we missing from “nature's sandbox”?
Deepwater fold and thrust belts offer unique opportunities for evaluating deformation in sedimentary successions with un- rivalled seismic imaging of fold-thrust structures. A regional seismic line through the Orange Basin, offshore Namibia, re- veals a classic paired, gravity-driven deformation system, over 100 km across, with extension high on the submarine slope and contraction toward the toe of slope. A mismatch between the minimum estimate of extension (44 km) and slip on thrusts (18-25 km) requires an additional longitudinal strain compo- nent of 18%-25% to be distributed across the system, most plausibly as lateral compaction and volume loss. Strains of this magnitude raise issues for understanding deformation in par- tially lithified strata, with implications for the applicability of theoretical fold-thrust models and the development of hydro- carbon resources in deepwater settings.