The Albatross basin underlies the southwest one-third of the Kodiak shelf, Alaska, and contains about 5 km of gently to moderately deformed rocks that are as old as late Miocene or Pliocene. The seaward limit of the basin is a large, northeast-trending anticline that underlies the shelf break.

The Dangerous Cape high, northeast of Albatross basin, is distinguished from the basin by shallow depth (1 to 2 km) to the base of reflective strata, by decreased relief of structures that underlie the shelf break, and by the central-shelf uplift. This uplift lies midway between Kodiak Island and the shelf break and is made up of several anticlines cut by numerous, northeast-trending reverse faults. Based on seismic evidence, deformed, nonreflective Paleogene rocks are inferred to unconformably underlie the less deformed upper Miocene or Pliocene reflective rocks.

Stevenson basin, northeast of the Dangerous Cape high, includes two subbasins that are separated by the northwest-trending Portlock anticline. The southwest subbasin contains as much as 4 km of rocks, and the northeast subbasin contains as much as 5 to 7 km.

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Rocks that fill both subbasins are probably as old as late Miocene or Pliocene and are gently deformed, except near the Portlock anticline and near the shelf-break uplift.

If hydrocarbon-source characteristics of rocks offshore are similar to those of rocks onshore, good hydrocarbon source rocks do not underlie the shelf. Eocene through middle Miocene rocks onshore, and upper Miocene or Pliocene rocks offshore, contain less than 0.5 wt % organic carbon, which is predominantly of herbaceous and humic orgin. The volume of total extractable hydrocarbons (C₁₅₊ Soxhlet extraction) from onshore Eocene through Miocene rocks ranges from 165 to 412 ppm. Offshore upper Miocene and Pliocene strata are thermally immature. Paleogene rocks, which are thermally mature, are the most likely sources for any hydrocarbons generated offshore, although indications are that they are low-quality sources.

Onshore Paleogene rocks generally have poor reservoir properties--porosities range from 1 to 10% but most are less than 5%, and permeabilities are less than 1 md. The best offshore reservoirs are probably in late Miocene and younger strata.

Structural traps for hydrocarbons include Portlock anticline, anticlines in the central-shelf uplift, and parts of Albatross Bank.

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