Dec 10 (Reuters) - Marathon Oil Corp said on Monday its chief operating officer, Dave Roberts, is leaving the company, and its shares slid more than 3 percent.

Allen Good, oil analyst for Morningstar, said Roberts was the company's 'voice' for the Eagle Ford shale, assets that are a big growth engine for the oil and gas company.

'The fact that he's leaving, people may take that as a negative,' Good said.

A spokeswoman for Marathon declined to provide additional details about Roberts' departure. His resignation is effective Dec. 14, the company said.

Marathon Oil shares fell $1.11 to $29.81 in late morning New York Stock Exchange trading.

(Reporting By Anna Driver; Editing by Leslie Adler) Keywords: MARATHON ROBERTS

(anna.driver@thomsonreuters.com)(713 210 8509)(Reuters Messaging: anna.driver@reuters.com@reuters.net)

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