By Kenneth Musante, CNNMoney.com staff writer October 21, 2008: 12:19 PM ET NEW YORK (CNNMoney.com) -- Oil prices fell Tuesday, briefly sliding below the $70-a-barrel mark, as talk of falling demand continues to weigh on the markets.U.S. crude for November delivery fell $4.20 to $70.05 a barrel, after dipping as low as $69.77.It was the expiration day for the November contract, often a signal for volatile trading. The December contract, which becomes active Wednesday, fell $3.76 to $70.63.Traders...
