The pictures were posted within a members-only group called Marines United, and were accompanied by vulgar and highly aggressive sexual messages.
The group has now been closed down.
"[This] is a direct attack on our ethos and legacy," said top enlisted marine Sgt Maj Ronald Green.
The Naval Criminal Investigative Service (NCIS) has also launched an investigation.
"This behaviour hurts fellow marines, family members, and civilians," said Sgt Maj Green in a written statement.
The Facebook group included around 30,000 active and retired male marines.