The studies on Arctic sediment that appear today in the journal Nature tell a dramatic story of polar warming and cooling over millions of years. But what they tell petroleum geologists may be just as striking. Though there is little mention of it in the papers, some scientists involved in the work said the huge amounts of organic material from dead algae and plants embedded in the ancient sedimentary layers suggested that the center of the Arctic Ocean could hold vast oil deposits.Several of the researchers said they were reluctant to focus on that aspect of the work, saying it would be unfortunate if their climate studies prompted new oil exploration that could liberate more greenhouse gases and further warm the climate. But one of the authors, Henk Brinkhuis of the University of Utrecht in the Netherlands, was not shy when he first pointed this out to reporters in 2004. This week, he said he remained confident that the prospect was real. "The entire Arctic rim is already one big exploration machine," Dr. Brinkhuis said. "I was nearly crucified for talking about this by some of the more politically environmentally friendly people out there. But it's a fact."