ANCHORAGE, Alaska - An oil exploration firm has discovered a deposit of potentially 1.8 billion barrels in Alaska's North Slope region south of Prudhoe Bay, the company said. Pantheon Resources PLC said it located the deposit along the Dalton Highway and Trans-Alaska Pipeline System corridor, The Alaska Journal of Commerce reported Wednesday. The London-based company made an updated evaluation of an old exploration well and used information gleaned from recent nearby drilling, officials said. The prospect, called Talitha, could be the latest in a series of big North Slope oil discoveries over the past five years.