I was going to say Omkalai from the description until I read this:
"....at the bottom of the ravine is the wreck of a PNGAF crashed Caribou..."
The PNGDF never owned or operated DHC4 Caribou. There is no PNG Air Force, only the combined PNGDF.
I think the only Caribou wreck the RAAF left in PNG was A4-233 which crashed in the Kudjeru Gap in August 1972, killing 21 school cadets, a liaison officer and the crew of 3.
The rest of the Caribous pranged by the RAAF were recovered.