THE NEW APPROACH FOR SUBDIVISION OF PLEISTOCENE NANNOPLANKTON ZONATION IN WAIPOGA-WAROPEN BASIN, PAPUA: CASE STUDY OF “T” WELL SECTION

THE NEW APPROACH FOR SUBDIVISION OF PLEISTOCENE
NANNOPLANKTON ZONATION IN WAIPOGA-WAROPEN BASIN, PAPUA:
CASE STUDY OF “T” WELL SECTION
Panuju∗
* PPPTMGB “LEMIGAS” Jakarta
Jalan Ciledug Raya, KAV. 109, Cipulir – Kebayoran Lama – Jakarta Selatan 12230 – Indonesia
Telex: 47172, Faximile: 62-21-7246150, P.O. Box:1089 Jakarta 10010, Phone: (021) 7394422,
7393958, 7394091, 7394856, 7394890, 7394901
Email: panuju@lemigas.esdm.go.id
ABSTRACT
Waipoga-Waropen Basin is placed in northern part of Papua on the island of New
Guinea. The gas discoveries had been made since 1958 in this basin, however, no
economic value of reserves lead to the not producing basin state until this time. The
main problem in Waipoga-Waropen Basin is great thickness of Pleistocene
sedimentary layers (until 7500m) as product of turbidite system (Wold & Barret, 2000).
This makes difficulty in well section correlation based on the conventional
biostratigraphy since individual layers within that section is being small part of biozone.
Many reworked nannoplankton as implication of turbidite deposit are also being
complicated aspect in biostratigraphic analysis.
The Pleistocene ranges from 1.806 m.a. to 11.550 k.a. It was the most recent episode
of global cooling or ice age took place. In nannoplankton biostratigraphy, this age is
characterized by the extinction of Discoaster brouweri (Discoaster group) at the bottom
and the first occurrence of Emiliania huxleyi at the top.
The quatitative nannoplankton investigation of “T” well has been done, and there is
evident that its sedimentary section gives the excellent nannoplankton assemblages to
subdivide Pleistocene age sediments of Waipoga-Waropen Basin (Zone NN19) into 9
subzones. Biomarkers from the bottom to the top consist of: LO of Discoaster brouweri,
FO of Gephyrocapsa caribbeanica, FO of Gephyrocapsa oceanica, LO of Cacidiscus
macintyre , LO of Helicosphaera sellii, FO of Reticulofenestra asanoi, FO of
Gephyrocapsa parallela, LO of Reticulofenestra asanoi, FO of Helicosphaera inversa
and LO of Pseudoemiliania lacunosa. The sediments belong to zone NN 20 that placed
in the uppermost part of Pleistocene were not analysed.