The hydrocarbon-bearing Oligocene Kugmallit Sequence is a siliciclastic unit comprising delta plain, delta front, prodelta and continental shelf-to-slope deposits, underlying over 20 000 km(2) of the Mackenzie Delta-Beaufort Sea. The delta front to base-of-slope deposits typically comprise massive- to parallel-bedded mudstone and sandstone, bioturbated to varying extents. Core samples from depths of 0.9 to 4.4 km, representing all the major deltaic depositional environments, form the basis of the petrographic study. The sandstones are fine-grained on average and range from very fine- to medium-grained. Sorting in all depositional environments is typically poor to very poor, though very well sorted sandstones occur sporadically. A marked increase in the proportion of chert grains, together with improved sorting, accompany increasing median grain size. The creation of secondary porosity, comprising over half of the present porosity, enhanced the permeability, even for the very poorly to poorly sorted sandstones. Relationships between depth-matched petrographic characteristics, petrophysical core measurements and wireline log values are evaluated. For very coarse-grained siltstones to medium-grained sandstones, a decrease in total gamma-ray count on logs corresponds to an increase in median grain size; also, the difference between the neutron and density log porosity values for this grain size range decreases with improved sorting. Rare carbonate-cemented sandstones are recognized on wireline logs by fast sonic interval transit times and by high density values. Computer-processed interpretations of entire wireline log suites, including high vertical resolution logs, showing output with dry clay and bound water separately, are most easily calibrated with detailed petrographic data. Preliminary results suggest that this type of calibration could improve the interpretation of sandstone properties over uncored intervals, particularly for sandstone units less than one metre thick.