Strata on the northern limb of the Purl Anticline record four main cycles of bathymetric change from bathyal to neritic water depths in the time interval from 6.15 +/- 0.35 Ma to 4.7 +/- 0.5 Ma (CK95 chronometric scale). The studied 2000 m-thick section extends from the uppermost Purl Limestone through the Orubadi Formation to the lowermost Era Formation, and includes planktonic foraminiferal zones N17B and N18. Within the Papuan Foreland Basin, in the Purl Anticline region, a proximal foredeep with water depths in the middle bathyal zone was present from 8.5 Ma or older to about 5.8 Ma (CK95). A rapid decrease in water depth of greater than 1000 m took place between about 5.8 Ma and 5.3 Ma with effective accumulation of about 270 m of mudstone (at present-day compacted thickness). This progradational phase of cycle 1 reflects the first major episode of compressional deformation causing uplift within the frontal part of the present-day Papuan Fold Belt during the Late Miocene and Pliocene. The progradational parts of the later cycles (II to IV, during the interval 5.3 Ma to 4.7 +/- 0.5 Ma), reflect subsequent tectonic pulses as the thrust belt propagated south toward the Purl region.