WASHINGTON—Facing a grim fiscal future made even more uncertain by the looming insolvency of Greece and Italy, the U.S. Treasury Department has announced the nation will switch over to a limestone-based economy beginning next Monday. "We're giving each American family 3 tons of Tennessee-quarried limestone, declaring 5 pounds of the rock to be equivalent to the value of one chicken, and then hoping people can figure it out from there," Treasury Secretary Tim Geithner said. "Sure, it may be a long shot, but we've more or less exhausted our options at this point. What do we have to lose?" At press time, speculators were driving up the price of limestone and creating an unsustainable bubble that will inevitably require a massive taxpayer bailout when it bursts.