Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Marathon Oil (NYSE: MRO) climbed as high as 11% in intraday trading Thursday after announcing plans to spin off its refinery business, creating two independent energy companies.

So what: The move is intended to free Marathon's promising upstream operations from its highly volatile, less-profitable, and capital-intensive downstream business, so it's no surprise that Mr. Market is applauding the decision. Marathon had previously considered the split in 2008 but held off on the move in the wake of collapsing financial and commodities markets.

Now what: Marathon Oil and the soon-to-be-public refining business, Marathon Petroleum, are both worth keeping a close eye on. For a number of reasons, both parents and their spin-off spawn traditionally trounce the market for several years following the split. Marathon's plan comes just a day after ITT (NYSE: ITT) said it would be splitting itself into three separate companies, so 2011 seems to be off to a very shareholder-friendly start. 

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Fool contributor Brian Pacampara owns no position in any of the companies mentioned. Try any of our Foolish newsletter services free for 30 days.

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