UBIQUITOUS TAR BALLS WITH A CALIFORNIA-SOURCE SIGNATURE ON THE SHORELINES OF PRINCE WILLIAM SOUND, ALASKA

Although tile shorelines of Prince William Sound still bear traces of the 1989 Exxon Valdez oil spill, most of the flattened tar balls that can be found today on these shorelines are not residues of Exxon Valde z oil. Instead, the carbon-isotopic and hydrocarbon-biomarker signatur es of 61 tar ball samples, collected from shorelines throughout the no rthern and western parts of the sound, are all remarkably similar and have characteristics consistent with those of oil products that origin ated from the Monterey Formation source rocks of California. The carbo n-isotopic compositions of the tar balls are all closely grouped (delt a(13)C(PDB) = -23.7 +/- 0.2 parts per thousand), within the range foun d in crude oils from those rocks, but are distinct from isotopic compo sitions of 28 samples of residues from the Exxon Valdez oil spill (del ta(13)C(PDB) = -29.4 +/- 0.1 parts per thousand). Likewise, values for selected biomarker ratios in the tar balls are all similar but distin ct from values of residues from the 1989 oil spill. Carbon-isotopic an d biomarker signatures generally relate the tar balls to oil products used in Alaska before similar to 1970 for construction and pavements. How these tar balls with such similar geochemical characteristics beca me so widely dispersed throughout the northern and western parts of th e sound is not known with certainty, but the great 1964 Alaska earthqu ake was undoubtedly an important trigger, causing spills from ruptured storage facilities of California-sourced asphalt and fuel oil into Pr ince William Sound.