Long-standing boss Todd Kozel, who last month decided to step down, has also rejected the chance to remain on the board as an executive director.
Kozel revealed in late June that he was stepping down from the top job at the annual general meeting, held on Thursday. It was envisaged that he would remain as an executive director on the board, but has turned this down. He will, however, remain as an officer of the Kurdistan-focused explorer, though the specifics of this job title were not made clear.
When Kozel decided to call it a day, chief operating officer Gerstenlauer was swiftly installed as interim chief executive, being named permanent in the position on Thursday.
Financial controller Mary Hood assumes the role of acting chief financial officer, replacing Ewen Ainsworth, who resigned recently.
Kozel was a co-founder of Gulf Keystone, having also founded Pittsburgh-based independent Texas Keystone in 1988. He served as president of the latter from 1995 to 2004 and has been a director since 1988.
He also founded US oilfield services player Falcon Drilling in 2001 and remains on the board.
Gulf Keystone is a major player in the Kurdistan Regional Government region of Iraq where it operates the Shaikan and Sheikh Adi blocks, while it also has interests in the Akri-Bijeel and Ber Bahr blocks.
The company is still in the process of exiting Algeria, where it entered in 2001.