Anomalously high porosities in the proto‐decollement zone of the Barbados Accretionary Complex: Do they indicate overpressures?

Abstract

Elevated pore pressures have been hypothesized to play a key role in the development of the decollement zones of accretionary complexes. Drilling within the proto‐decollement zone of the Barbados accretionary complex revealed anomalously high porosities up to 6 km seaward of the deformation front. Defining whether the high porosities are a reflection of overpressures is critical for understanding the seaward propagation of the decollement zone. In this investigation, we used numerical modeling to assess whether the high porosities reflect overpressures due to sedimentation. From this work, we concluded that reported permeabilities are not low enough to produce overpressures, even if additional fluid were contributed from areas of greater sedimentation. Furthermore, overpressures within the proto‐decollement zone are demonstrated to be inconsistent with normally compacted underlying sediments. Locally anomalous sediment strength provides a more likely explanation for the observed high porosities.