The Lower "T.f" Letter Stage is now widely accepted to be the later part of the Early Miocene and the lower and middle parts of the Middle Miocene (c. 21 to 12 mybp). This convention follows Adams (1970), although the mass extinction of larger forams at about 12 mybp was the event that was first proposed as the top of Tf. What we now call Upper Tf was originally "T.g" (Leupold & van der Vlerk 1931). It is important to note that the T.f 1 to 3 subdivisions have different meanings to different workers.
The images shown here are reduced to about 1/5 their original resolution and highly compressed as JPG files. Original images available on request, as TIF files from 120 to 600 MB in size
- Early to mid- Middle Miocene Limestone (744 KB). This sample is from near the type location for Cycloclypeus annulatus Martin, on the NE side of the Jatiluhur reservoir-lake in West Java. Mudstones interbedded with these limestones contain both Orbulina and Globorotalia mayeri indicating a Middle Miocene age. The very large Lepidocyclinids are microspheric forms (B generation), and such large B-forms are not uncommon in limestones of this age. The sample also contains Multilepidina, and some embryonts of this type can be seen on the original image, but are not clear on this reduded file. It is not known if the very large B-forms are related to the Multiplepidina lineage, although they both have similar stratigraphic ranges.
- Early Miocene Limestone (248 KB). This sample is from above the type Prupuh Limestone in N.E. Java. It lacks the T.e markers Eulepidina and Spiroclypeus, but has typically T.f Lepidocyclinids such as the pillared L. aff. ferreroi. Also present are well preserved examples of Austrotrillina howchini with branched alveolae in the thickened test walls
- early Middle Miocene sandy limestone (568 KB). From Madura island. Very good preservation with blue epoxy impregnation highlighting pore and stolon features in Lepidocyclina, Miogypsina and others
- Badui Beds, West Java (180 KB). This sandy carbonate sample has been thin sectioned and disaggregated, with individual Miogypsinids examined for biometric properties. The common specimens with partings in the lateral walls were assigned to a new genus, Miogypsinodella by Boudagher-Fadel et al. 2000, from sediments of the same "mid-Tf1" age as the Badui Beds, from north Borneo. In the Badui beds every one of these specimens proved to be a microspheric form, presumably the alternate generation to the macrospheric forms also seem in the sample. While Boudagher-Fadel et al. do illustrate a macrospheric form of their Miogypsinodella it is an equatorial sections from a whole rock thin section, and therefore there is no way of knowing what the lateral chambers were like in this specimen. Therefore it is strongly suspected that this genus is invalid, as it is a morphotype representing the haploid stage of Miogypsina. This picture shows both forms from a sample dated on nannofossils as NN4.
- Early Miocene limestone (640 KB). An unusual sample, actually one of van Bemmelen's field samples from the Sigugur Limestone, North Central Java [Blad 66-253]. This sample should be considered in light of the notes in the petrology section on the Lutut Formation which is age equivalent and located not too far to the east. In both areas the youngest age fauna is Tf1, later Early Miocene. Lutut has abundant Early Oligocene clastic reworking with N. fichteli and lesser Late Oligocene carbonate reworking. At Sigugur there is abundant Late Oligocene carbonate reworking - in fact the Sigugur Limestone outlier is a large olistolith / olistoliths. This is the light grey lithology in this image. The brown stained limestone contains some clastic grains, a single N. fichteli, and much younger Miocene forms (advanced Miogypsina). The contact between them is obviously an ancient erosional surface, with calcite crystals lining an broken vug. The whole sample is a hard piece of limestone.
