Canada Southern Petroleum ( CSPLF) has agreed to be acquired by a unit of Canadian Oil Sands Trust in a $146 million deal. Each share of Canada Southern, a Calgary-based energy company, will be bought for $9.75 in cash. Canada Southern had been sought by both Canadian Superior Energy ( SNG) and Petro-Canada ( PCZ) before it reached the arrangement with Canadian Oil Sands. Under the terms of the agreement signed Sunday, Canadian Oil Sands, an investment trust, has the right to match any offer made by another bidder. Shares of Canada Southern were surging $1.44, or 16.4%, to $10.21 on seven times its normal volume, suggesting investors believe the final offer has yet to be made.