Subsurface stratigraphic picks of the Middle–Upper Triassic Shublik Formation, Alaska North Slope

The Middle–Upper Triassic Shublik Formation is the main source rock for Arctic Alaska oil and gas accumulations, including the supergiant Prudhoe Bay field. A revised stratigraphic framework recently has been developed in outcrop for the Shublik and related strata that delineates three large-scale stratigraphic units: 1) the lower clastic (LC) unit, 2) the middle carbonate-chert (MCC) unit, and 3) the upper clastic-carbonate (UCC) unit. The three stratigraphic units were interpreted to comprise five transgressive-regressive (T-R) sequences (LC1, MCC1, MCC2, MCC3, and UCC1). This outcrop-based framework has been extended to the subsurface of the Alaska North Slope using gamma-ray logs from 161 exploration wells. Subsurface stratigraphic picks of the five T-R sequences within the Shublik Formation for each well are documented herein.