The Shublik Formation is a heterogeneous unit consisting of several distinct facies, including: (1) fossiliferous sandstone or siltstone; (2) glauconitic sandstone or siltstone; (3) siltstone, calcareous mudstone, or limestone with phosphate nodules; and (4) black, calcareous mudstone or black limestone, usually fossiliferous. This sequence of lithologies is interpreted as having been deposited along an onshore-offshore (north to south) gradient. Bioturbation of the sediments is variable but generally decreases offshore. Organic carbon increases offshore, and phosphate increases from the paleoshoreline and decreases again farthest offshore.

The distribution of glauconite, phosphate, and organic-carbon-rich rock is consistent with the facies expected in an upwelling zone that has a well-developed oxygen minimum. Glauconite is consistent with dysoxic conditions, and well-laminated, organic-carbon-rich rock in the offshore facies is consistent with anoxic conditions. High biologic productivity coupled with normal oceanic circulation may have caused the basin's low-oxygen conditions, as indicated by the presence of phosphate nodules and the extreme abundance of bivalves that have been interpreted to be pelagic. Phosphate indicates a high rate of supply of organic matter to the sediment-water interface, where it was mobilized from the organic matter within the anoxic zone and reprecipitated at the zone's edges. Pelagic bivalv s (Monotis and Halobia) are present in such large numbers as to suggest unusually abundant food supply; in addition, their distribution is consistent with mass kills, which are common among fish in upwelling zones.

Although an open-ocean divergence was predicted previously for the North Slope region in the Triassic, the distribution of the facies of the Shublik Formation relative to the paleoshoreline and the rapidity of the facies change onshore to offshore are more consistent with a coastal upwelling zone.

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