Upper Triassic carbonate, volcanic and clastic rocks deposited in the Whitehorse Trough, a Mesozoic forearc basin, are well-exposed at Hill 4308. The deposition of these rocks occurred in three distinct stages: 1) sedimentation of lime sands and clastics on the flank of a volcanic high, 2) development of reefal carbonates and associated limestones, and 3) renewal of clastic deposition with both erosion and continued growth of patch reefs. The reefal carbonates are similar in structure and composition to reefal carbonates at Lime Peak about 6 km to the south, but the stratigraphic section at Lime Peak differs from that at Hill 4308, the former representing more continuous deposition of carbonate on an underlying clastic foundation. Differences between Hilll 4308 and Lime Peak may reflect local variation in relative sea level and in the distribution and intensity of clastic sedimentation experienced by nearby localities in tectonically active areas.
