Under construction
Cribrohantkentina inflata (80 KB). This specimen is from a thin, condensed layer at the top of the Nanggulan section C. Java above the Tb limestone illustrated elsewhere on this site. Extremely well preserved planktonic assemblages occur here from N16 to basal Oligocene N18, above which the facies becomes more chalky and overgrown.
A small species of Cyclammina (image 28 KB) with a high number of chambers per whorl and relatively thin walls for the genus. This specimen is half a millimetre in size, has slightly less than the optimum 16-19 chambers per whorl but otherwise matches the species description for Cyclammina pusilla Brady. This specimen is from the early Oligocene section at Cikalong in West Java. An unpublished location, where even the age of the thick sediments was uncertain until recent work. Cyclammina pusilla is a deep marine restricted species, found by Brady only between 1675 and 1900 fathoms [3350-3800 metres], and it occurs at this site in poorly fossiliferous beds, where some sediments contain arenaceous forams but very few samples have any calcareous fossils. When plankton is present the species Cassigerinella chipolensis and Chiloguembelina cubensis identify the age as Early Oligocene. In this mixed silty mud and quartz sand - conglomerate unit there are a few limestones and sandy limestones with Tertiary c larger foraminifera including the example in the illustrations for Letter Stage T.c (Basal Oligocene Limestone)
Stereo-paired images of very well preserved foraminifera from a sample at 4 metres in the Kali Kunir Trench, upper Nanggulan section (Image file 104 kb). Zone P18, basal Oligocene. In this view is a sample of "Turborotalia" ampliapertura (the large specimen), with numberous small biserial Chiloguembelina cubensis, the small flat, planispiral Pseudohastigerina micra, and two specimens of the biserial but coiled Cassigerinella chipolensis. These last two prove the zone P18, the other two range from Eocene to mid Oligocene.
The T. ampliapertura specimen is 470 µm maximum (top-bottom) dimension.
Note that many of these age index species are close to 100 microns in size, and a large proportion, especially the dart-shaped C. cubensis will pass through a 106 micron sieve. It is therefore essential to sieve all microfossil residues, especially those from the Early Oligocene, with a 63 micron (230 mesh) sieve.
Stereo-paired images (52 kb) of Spiroplectammina spectablis a useful, Eocene and older arenaceous foram from P16 mudstones at Kali Kunir, Nanggulan. The maximum dimension of the main specimen is 1010 microns. The specimen is tilted up to make the aperture visible.
Stereo-paired images (66 kb) of aff. Anomalinoides rubiginosus from the Latest Eocene P16 at Nanggulan, C. Java. This species is part of a plexus of forms ranging from A. rubiginosus in the Paleocene, through A. grosserugosus, A. capitatus, A. semicribratusus and A. globulosus up into the Pleistocene. This is a relatively large form, the maximum dimension of the upper specimen is 1,115 microns.