On March 24, 1989, the Exxon Valdez supertanker grounded on Bligh Reef
, spilling North Slope crude oil into Prince William Sound, Alaska. Tr
acking the geochemical fate of this spilled oil has revealed, in addit
ion to weathered products from the spill, minor oil residues on beache
s from a distinctly different source. By using carbon isotopic composi
tions of whole-oil residues as a principal method of identification, w
e found that the deltaC-13 values of Exxon Valdez oil (one sample) and
its residues (eight samples from six islands) average -29.3 +/-0.1 pa
rts per thousand. In contrast, the non-Exxon Valdez residues (15 sampl
es from 12 localities) have an average deltaC-13 value of -23.8 +/- 0.
1 parts per thousand. This tight distribution of carbon isotopic value
s suggests a single event to explain the non-Exxon Valdez residues. Th
is event likely was the Great Alaska Earthquake of March 27, 1964. Thi
s quake and the subsequent tsunami destroyed asphalt storage facilitie
s at the old Valdez town site, spilling asphalt (deltaC-13 = -23.6 par
ts per thousand) into Port Valdez fjord. From there the asphalt appare
ntly advanced south into the sound. Thus, the possible connection betw
een two Alaskan catastrophes, separated by 25 yr, is found in the mino
r oil-like residues that continue to mark the two events on the beache
s of Prince William Sound.