Thick, apparently layer-cake, proximal carbonate platform deposits of the Natih Formation (Late Albian - Early Turonian) show stratigraphic heterogeneity that differs between transgressive and regressive stacking patterns of high frequency cycles. In Natih Sequence I (E member), stylolite-seamed mudstones to wackestones of deepening half-cycles form permeability barriers in landward stepping configurations, as do the dolomitised, early-cemented bed tops of progradational half cycles in seaward stepping mode. These laterally extensive permeability barriers, spaced at 1m to 10m intervals, should be taken into account when putting together models for fluid flow in similar thick "homogenous" reservoirs.