Sarah Irving has been appointed executive vice president of the company, according to an Irving Oil statement, which also announced a new company president and chief operating officer, both family outsiders.

Sarah Irving becomes the first of 85-year-old Arthur Irving's children to hold a senior position at the company, headquartered in Saint John, New Brunswick, since Arthur's son Kenneth resigned as president in 2010.

Irving Oil operates Canada's largest oil refinery, its biggest deepwater oil port, and is a partner in TransCanada's giant Energy East oil pipeline project.

"Ms. Irving maintains a broad perspective on our business, having grown up in the refining and marketing business," the company said in the press release. "Recently, Sarah completed her MBA and has returned home to Saint John to contribute to our company’s success as a senior leader."

The company said Deloitte LLP partner Ian Whitcomb was appointed president of the company, and refinery manager Mark Sherman was promoted to vice president and chief operating officer.

Whitcomb's appointment follows a whirlwind of resignations from the senior post since Kenneth Irving resigned in 2010 under unclear circumstances. Whitcomb replaces former Thermal Products Chief Executive Paul Browning who left last year, and ex-Suncor executive Mike Ashar who left in 2013.

Ashar filed a C$50 million lawsuit in March saying he had been underpaid, a claim denied by Irving.

Arthur Irving, widely believed to continue to run Irving Oil behind the scenes, has amassed a personal fortune of about $5.5 billion, according to Forbes Magazine. Since Kenneth's departure from the company, questions over who will take over company ownership after Arthur have intensified.

(Writing by Richard Valdmanis; Editing by Meredith Mazzilli)