Carbonate-Siliciclastic Interactions in the Cenozoic Mixed Depositional System of the Gulf of Papua. (Papua New Guinea)

A late Oligocene - middle Miocene extensive neritic carbonate system thrived in the Gulf of Papua (GoP) adjacent to emerging fold and thrust belts which ultimately formed the Island of Papua New Guinea (PNG). This was a time when the accumulation of siliciclastics, weathering products of the rising mountains, was restricted in the Aure Trough, a proximal foreland basin bounding the carbonate province.

The burial of the carbonate system, initiated during the late Miocene - early Pliocene rise of the PNG Central Mountain Ranges, occurred mostly during the early late Pliocene renewed uplift of the Papuan Peninsula. This strong tectonic pulse creating Papuan mountain chains more than 4 km in elevation, enormous volumes of siliciclastics, which production was also enhanced by the “mid” Pliocene (3.6-2.9 Ma) global warmth, higher atmospheric carbon dioxide, and contemporaneous East Asian monsoon intensification, were transported into the GOP by several rivers. The siliciclastics filled up several 2-4 km deep offshore troughs and buried most of the pre-exiting carbonate neritic system to form a continental shelf with a surface area exceeding 20,000 km2 and a shelf edge prograding as much as ~150 km, forming more than 80% of the modern shelf in less than 1 My.

In spite of this huge influx of siliciclastics, widespread contemporaneous occurrences of elongated ephemeral carbonate edifices are observed on the outer shelf edges in particular during time of continental shelf paired vertical aggradations and lateral progradations. Intermittently enhanced El-Nino conditions during the warmest early late Pliocene intervals could have slow down the siliciclastic flux into the GoP to allow the growth of shelf edge carbonate edifices during times of early transgressions.