OFR 151.pdf - CRC LEME

8.2 Results in prospect (recommendations)
Plants and animals, and the communities within which they co-exist, are evolutionary
responses to climate, not organic equivalents of the thermometer or rain-gauge, and this will
have been true of their Cretaceous and Tertiary predecessors. Similarly, many of the caveats
identified in this and an earlier review (Macphail et al. 1994) are unlikely to be resolved in the
near future. Nevertheless the scale of this review does suggest ways in which palaeobotanical
evidence can be better mined to meet CRC-LEME objectives.
8.2.1 Samples
The review of old exploration reports and borelog data held by the State geological surveys
indicates that, contrary to expectation, thin carbonaceous units are preserved in subcrop in
many sub-humid, semi-arid and arid regions of the continent. However in New South Wales,
and presumably in other states, much of the conventional core that is archived in core libraries
is Palaeozoic or older. This problem is exacerbated by deep-weathering of much of the
Cretaceous and Tertiary regolith and, with few exceptions, outcrop samples submitted for
palynostratigraphic dating by CRC-LEME have proved to be barren, even though potentially
fossiliferous intervals occur below the weathering front in the same time-rock unit.
Unlike in the 1960s-1980s, the current emphasis on geophysical and remote sensing (GIS)
techniques makes it increasingly unlikely that routine stratigraphic holes will be drilled to
resolve geological problems. Nonetheless, this short-fall can be circumvented in at least four
ways to extend the existing palaeobotanical database:
1. Improved networking
Numerous boreholes continue to be drilled in many areas for infrastructure projects such as
bridges, roads and groundwater, but organic sediments brought up to the surface almost
always are discarded by the drillers because "no-one knew anyone would be interested in
them" [comment to author, 1995].
Formal networking with geologists employed by the State authorities responsible for
groundwater and rivers, mining, and private sector borehole drilling services arguably
provides the best alternative means of recovering fossiliferous sediments in inland Australia
(cf. Macphail 1997b). One example of the benefits of such networking occurred in the mid
1980s when an interested workman bulldozing roads on the Central Plateau for the Forestry
Commission of Tasmania uncovered the world class Tertiary macrofossil deposit at Little
Rapid River (R.S. Hill pers. comm.).
2. Analysis of RAB cyclone samples
Analyses made in the course of this study have shown that well-preserved microfloras can be
recovered from medium to dark grey dust samples collected from the cyclone during RAB
drilling, arguably the cheapest and most commonly used form of drilling in hard-rock mineral
exploration at present. Because the cover beds are often deeply weathered, the only
contaminants found in these other types of ditch cuttings samples are easily recognised
modern pollen types (Macphail 1999).
3. Palaeontological collections
Blocks of sediment encasing Cretaceous and Tertiary macrofossils often preserve diverse
plant microfloras. The State geological surveys, museums, and some former technological
117