Diverse nonmarine and shallow marine deposits blanketing the coastal plain and continental shelf of northern Alaska are known collectively as the Gubik Formation. In the Beaufort coastal region between Barrow and Prudhoe Bay and along the Chukchi coastline southwest of Barrow, five distinct marine subunits have been recognized within the Gubik, ranging in age from middle Pliocene to late Pleistocene. A sixth pre-Holocene transgressive marine subunit, about a meter thick and bearing abundant ice-striated dropstones that originated in the Canadian Arctic Islands, is present along much of the Alaskan Beaufort coast. The aggregate thickness of the Gubik Formation on the coastal plain is no more than a few tens of meters. Offshore beneath the Beaufort shelf, however, the Gubik Formation is locally thicker than 100 m and includes not only deposits that probably correlate with those mapped onshore but also subunits of intermediate and younger ages. These have been studied mainly through the interpretation of a network of high-resolution seismic reflection profiles that covers most of the Alaskan Beaufort shelf at 18 to 35-km intervals seaward of the 25-m isobath.

In general, the Gubik Formation offshore appears to be a stack of wedge-shaped transgressive marine units that thicken toward the shelf break, beyond which they are disrupted by active slumps and landslides. This idealized geometry is altered in the area east of Canning River, where active faulting and folding have created persistent local highs and depocenters, and in the area between Smith and eastern Harrison Bays, where a complicated Quaternary drainage history has resulted in extensive local erosion of the marine wedges and in the deposition of relatively large deltaic sequences.

Accumulation of the marine wedges must have occurred during periods when depositional rates were considerably higher than at present, perhaps during deglaciations of the Canadian Arctic Islands, when great volumes of sediment-bearing ice are likely to have been debouched into the Arctic Ocean.

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