SAN FRANCISCO (MarketWatch) -- Oil and gas stocks took it on the chin with the rest of the stock market early Thursday, giving up the prior session's mild gains with 7% drops from Alpha Natural Resources ANR -6.94% , Helmerich & Payne HP -6.17% and Nabors Industries [s:nbr] weighing heavily. The NYSE Arca Oil Index XX:XOI -3.75% and the NYSE Arca Natural Gas Index XX:XNG -3.49% both shed almost 4% while the Philadelphia Oil Service Sector Index OSX -4.82% lost 5%. Crude oil fell more than 3% to $84.97.
