CHAPTER 4
 EVOLUTION OF HIGH PORE PRESSURES AND IMPLICATIONS FOR EPISODIC
 FLUID FLOW AT THE NORTHERN BARBADOS ACCRETIONARY COMPLEX

 Introduction

 Variations in fluid flow pressures and its distribution within subduction zones

regulate the mode of deformation, affecting the evolution of the accretionary complex. It

has been speculated that excess pore pressures play a major role in the mechanics of

thrust faulting (Hubbert and Rubey, 1959), thus, allowing the weak semilithified

sediments in accretionary complexes to glide over the subducting plate along a low-angle

detachment surface (Davis et al., 1983). Excess pore fluid pressures are also responsible

for increasing sediment permeability associated with reduction in effective stress (Yeung

et al., 1993; Fisher and Zwart, 1996). In addition, pore pressure has been claimed to

influence seismogenic faulting, through its control on effective stress and consolidation

state (e.g., Moore and Saffer, 2001; Scholz, 1998). Thus, an understanding of the

development of excess pore pressures will provide valuable insight to the evolution of

accretionary complexes as well as to subduction zone processes such as fault mechanics.

 The abundant evidence for excess pore pressures at Barbados accretionary complex

provides an excellent opportunity for the study of evolution of pore pressure generation.

The distribution of mud volcanoes (Gretener, 1976) and the overall shape of the

accretionary prism (Davis et al, 1983) suggest the existence of excess pore pressures at

the Barbados accretionary complex. In addition, elevated pore fluid pressures have been

inferred at the Barbados accretionary complex from fluid flow modeling (e.g., Shi and