This study is mostly based on sediment samples (prefixed with "Kakahu-") of about 300-500 g, although more was collected where macrofossils were obvious. The material which was published by
Pole (1997) was collected by G. Mason around 1987-89, and by myself and J.D. Campbell in 1990. I have visited the area in most years since but the two original localities have since been trampled by livestock, weathered, and overgrown. Therefore, in 2003 a mechanical ditch-digger was employed to dig a hole at one of these localities (Wellman's "Clay Pits") to try and relocate the richly fossiliferous horizon. The digger removed mud which had accumulated over the bottom of the old pit and then dug about 2 m into in-situ sediment. The main fossil horizon was not rediscovered. However, scattered plant fossils were found preserved as dark, carbonaceous layers, with some cuticle preserved. These included dense layers (about 10 mm thick) of conifer leaves. Angiosperm leaf fragments tended to be scattered individually or concentrated on single bedding surfaces. The fossils in this material appear to lie within
Wellman's (1953) K3 zone of dark clay. Wellman's K7 zone of 'leaf beds' from the Clay Pits lies about 35 m stratigraphically higher and has not been relocated.
Wellman (1953) published a stratigraphic column for the 'Clay Pits' locality on Rapuwai Road, which covers samples Kakahu-20 and 27-31, and for the roadside 400 m to the west, which includes samples Kakahu 1-3. Wellman's stratigraphy had an advantage of being partially based on numerous boreholes, and in the years since there has been a reduction of outcrop and quarrying, and some of his stratigraphic details are difficult to recognise now. The relative stratigraphic positions of some samples are therefore difficult to determine precisely due to lack of outcrop continuity, but
Figure 2 summarises stratigraphic understanding. From their general location in the valley of Bush Creek, it is clear that samples Kakahu 15, 16, 17 and Kakahu 24, 25, 26 will be among the youngest, lying very close to the coral bed of the overlying marine sequence, while sample Kakahu-23 is likely to be one of the oldest. Sample Kakahu-1 is considered to be from the lignite indicated near the base of
Wellman's (1953) column 400 m to the west of the Clay Pits.
In 1990 leaf material was also collected from fallen blocks at the base of a cliff forming
Wellman's (1953) locality, "Road-side 20 chains west of Clay Pits." Several hours in 2003 were spent on the end of a rope trying to collect in situ leaf material from the mudstone horizon in the cliff, but this was also unsuccessful. Wellman correlated the leaf beds at this locality with his leaf beds at the Clay Pits.
New macrofossil localities were searched for but with the exception of Lygodium fronds and monocot leaves on one bedding surface in the quarry by Hanging Rock Road, no more were located.. Details of these localities are given in
To prepare leaf cuticle, samples were broken down into a sludge using hot water and hydrogen peroxide and the resulting material sieved, retaining what did not pass through a 1 mm mesh. The remaining organically preserved plant fossils could be cleaned in hydrofluoric acid, or be reduced to cuticle using a 10% solution of aqueous Chromium Trioxide and stained with Crystal Violet. Cuticle fragments were mounted on microscope slides in Thymol Glycerine-jelly, or mounted on Electron Microscope stubs with double-sided tape and platinum coated. As the affinities of most angiosperm cuticle taxa are not known, and there is no established way of grouping the morphologies hierarchically, they described using a parataxon code, consisting of a string of letters. These are essentially species without genera. For previous use of this system see
Palynological samples were processed using a standard procedure of hydrofluoric acid, nitric acid, and were mounted on microscope slides in thymol glycerine jelly. Individual pollen grains are located using England Finder coordinates. Charcoal grains >20 um in length were also counted (Singh et al. 1981;
Martin 1996). These were identified as very black, highly reflective, angular fragments, often with well-preserved cellular detail and a homogenous, translucent sheen in TLM. To confirm this identification, a sub-set of samples was boiled in concentrated nitric acid for one hour and washed with 5% ammonium hydroxide solution. Cell-wall structure of some specimens was also observed under SEM and noted to be homogenised.
All material is stored in the Queensland Herbarium (AQ).