Marathon Oil Corp. reported lower fourth-quarter sales volume, though the crude oil and natural gas producer’s bottom line grew 16% due to fewer income tax provisions. The company had generally posted higher production in recent periods, boosting earnings. Marathon, which has focused on drilling in oil-rich unconventional fields since it spun off its downstream and petroleum operations in 2011, has boosted investments in U.S. oil plays such as shale formations like the Bakken in North Dakota. For the latest quarter, Marathon Oil posted a profit of $375 million, or 54 cents a share, up from $322 million, or 45 cents a share, a year earlier. Excluding asset sales, adjusted profit from continuing operations rose to 60 cents from 55 cents a share. Revenue fell 22% to $3.29 billion. Analysts surveyed by Thomson Reuters expected a profit of 71 cents a share on $3.57 billion in revenue. […]