UPDATE 1-BHP names Ken MacKenzie as new chairman

(Adds details, context)

SYDNEY, June 16 (Reuters) - Mining giant BHP Billiton on Friday named former Australian packaging executive Ken MacKenzie as its next chairman.

MacKenzie, 53, succeeds Jac Nasser, as of September 1 at a time when the world's biggest miner is being challenged by activist investors to overhaul its structure.

MacKenzie presided over a long-stretch of prosperity at Amcor Ltd, which makes packaging for food producers, industrial companies and pharmaceutical firms, that coincided with the end of a boom period for mining companies.

Hedge fund Elliott Management has maintained a barrage of criticism against Nasser and BHP Chief Executive Andrew Mackenzie since publicly releasing a roadmap of changes it wants at the company, most notably an exit from U.S. oil and shale businesses.

On Wednesday Elliott called for a board shake-up, blaming long-tenured directors for bad investments and ill-timed share buybacks.

That could place MacKenzie, who joined BHP's board just last year, in good standing with Elliott. Regarded as highly focused on capital discipline, he replaced 75 percent of Amcor's top 80 managers in his first two years at the company.

Nasser has defended the company's $20 billion investment in shale acquisitions in 2011 against Elliott's criticism.

BHP also faces a key juncture in the Samarco mine dam liability saga in Brazil, which is due to be settled in September.

A burst dam at Samarco, a joint venture between BHP and Brazil's Vale, killed 19 people and caused the country's worst ever environmental disaster in late 2015, when mud and waste destroyed a village and polluted the Rio Doce river.

Despite being the world's biggest mining house, BHP has a history of appointing executives from outside the sector as chairs. Since 1984 only two out of six chairmen had mining backgrounds.

(Reporting by James Regan; Editing by Richard Pullin)