Detailed reconnaissance gravity surveys in the Deer Lake Carboniferous basin have been conducted using a station spacing of 2.5 km. The digitized aeromagnetic data for the basin were reduced to a 1:253 440 scale composite map. These two data bases were used to determine the configuration of major features and the total sediment thickness at various locations in the basin. Preliminary seismic results from reflection and refraction seismic surveys planned on the basis of these results are discussed. Modelling of gravity and magnetic data indicates that the Humber syncline contains approximately 1.2 km of sediments underlain on the west by rocks similar to the Long Range Complex. The eastern limb of the syncline is underlain by rocks similar to the Gull Pond Igneous Suite. The Howley Formation is deduced to be approximately 1.5 km thick and floored by rocks similar to the Topsails Igneous Suite.