TORONTO — The Toronto stock market tumbled more than 100 points Thursday as energy stocks sold off and crude prices plunged to multi-year lows — below US$70 a barrel — after the OPEC cartel decided not to cut oil production.The S&P/TSX composite index dropped 115.97 points to 14,922.44. Trading volumes were lower than usual with American markets closed for the U.S. Thanksgiving holiday.The energy sector lost seven per cent while the January crude contract was down $4.64 to a 4 1/2 year low of US$69.05 a barrel in electronic trading on the New York Mercantile Exchange late in the afternoon. Major decliners included Pengrowth Energy (TSX:PGF) and Precision Drilling (TSX:PD) , both down almost 13 per cent.There had been hopes that OPEC oil ministers meeting in Vienna would cut production in order to put a floor under prices that have fallen about 30 per cent since mid-summer, when they were elevated by geopolitical worries. Prices have steadily fallen since then because of a strengthening greenback, lower demand prospects and, mainly, a glut of oil.But OPEC will keep its production unchanged at 30 million barrels a day and that means bad news for the TSX energy sector, now down about 14 per cent year to date.“In the short term, it’s so challenging,” said Norman Raschkowan, senior partner at Sage Road Advisers, who said he believes some of the smaller players are particularly exposed.“We will get to a spot where (dividend cuts) start to happen and especially with some of the smaller and more speculative names whose share prices were being supported almost exclusively by their dividends. Their distribution probably exceeds their cash flow and they have to think about cutting — and if they don’t think about it, their bankers will.”Lower oil prices are starting to bite into Canadian provincial finances. The Alberta government now expects a barrel of oil to trade at an average of US$75 a barrel for the rest of the fiscal year ending next March. The energy sector generally accounts for about 25 per cent of the province’s total revenue. Tumbling oil prices pushed the Canadian dollar down 0.75 of a cent to 88.25 cents US.Gold prices also headed lower with February bullion off $7.10 to US$1,190.40 an ounce, pushing the gold sector down about one per cent.March copper was unchanged at US$2.95 a pound and the mining sector ticked 0.8 per cent lower. In the corporate front, Rio Tinto said Thursday that it has approved a plan to spend US$350 million over four years to expand its Diavik diamond mine in Canada. Rio Tinto holds a 60 per cent stake in the Diavik joint venture, while Dominion Diamond Corp. (TSX:DDC) holds the remaining 40 per cent. Dominion Diamond gained 39 cents to $18.65.Other sectors lending support to the TSX included industrials and financials, both ahead 0.5 cent.