The Australian Geologist - Geological Society of Australia

eports, but also a good number of summaries
of previously published work. The
editors’ comment in their preface that this
book does not contain all regolith-landscape
environments in Australia, but a goodly
number are covered.
I begin with the ‘Supporting Chapters.’ The
first is by RR Anand on ‘Weathering history,
landscape evolution and implications for
exploration.’ This chapter begins most unfortunately
with a major omission in the first
paragraph where the figure caption symbols
do not match those on the map portrayed. A
fairly annoying start to ones read when there
are some 352 pages to go. Regolith is a relatively
new part of the geological sciences
and as such needs to be clearly and concisely
explained before delving into a number of
detailed and complex case studies. This
Chapter uses old and often out of date references
to fundamental geological and regolith
knowledge of Australia, sometimes quotes
incorrect references, and does not once refer
to the most recent Australian regolith geology
book available in the market place. This
first chapter in the book does not use the
contemporary international geological time
scale, which I might add is a fault with many
of the case studies as well, suggesting they
have not been edited with current geological
time scales in mind. Apart from the specific
problems I have mentioned this chapter is
generally poorly organised; a shame for the
first chapter of a major work on Australian
regolith geology.
Chapter 2, ‘Geochronology’ sits in a prominent
position in the book which is entirely
appropriate as dating of regolith materials
and as a consequence landscape evolution is
one of THE major problems in this research.
Pillans has outlined the problems with some
examples of their resolution in regolith
materials. The discussion is limited, simply
pointing out that different mineral phases in
regolith materials can be expected to have
different ages, and that the subaerial preservation
of pre-Cenozoic weathering materials
must involve burial and exhumation even
though erosion rates in Australia are generally
low. This being so he does not go on to
explain how in a low erosion environment
the profiles become covered (erosion must
occur somewhere near by) and then be
exhumed, presumably by erosion. I also
believe that it is difficult to preserve many
regolith-formed minerals in deeply buried
situations as they are unlikely to be in
mineralogical and chemical equilibrium with
the new buried environment. An interesting
conundrum not explained here or elsewhere
in this volume where burial and exhumation
is invoked. This Chapter provided paleomagnetic
ages from some 30 sites round
Australia, but does not discuss the implications
of these Fe-oxide ages, a shame
because the Fe-mineral components of
regolith change character as water and
chemical conditions change over time.
Craig’s Chapter 3 is excellent and gives a
good overview of the techniques and problems
associated with regolith mapping. He
clearly describes the methods used in
regolith terrain mapping as developed in
Australia based on the early CSIRO methods
of land system mapping. This chapter
describes the data collection techniques and
the use of modern electronic data acquisition
technology and how this is combined with
remotely sensed data sets using GIS applications
to produce maps of regolith terrains.
Such maps he reports are useful in mineral
exploration, salinity studies and I venture to
add will become increasingly important in
other natural environmental applications.
Australia has developed the most advanced
system of regolith mapping in the World, not
least due to the efforts of this author.
Chapters 4 and 5 briefly introduce Australia’s
contemporary climate and vegetation.
Chapter 4 by Butt gives maps of modified
Köppen climate classifications and a summary
table of the classes. Chapter 5, also by
Butt, is based on the vegetation classification
in the Australian Native Vegetation assessment
and divides it into 23 major pre-
European settlement floristic groups along
with maps of cleared and modified vegetation
and one of basic geological subdivisions
of the continent. He draws some floristic and
geological relationships from the data. These
chapters provide contemporary background
knowledge of the continent and a context for
the present conditions under which regolith
materials exist. Apart from this I am not sure
why they are included as there is no explanation
of how these relate to the evolution
of either regolith or landscape history I feel
a chapter on paleoclimate and vegetation
evolution in Australia could more profitably
replace or be added to illuminate better
many of the case studies that follow.
It is not my intention here to go thorough
each of the case studies but rather to touch
on some themes that emerge from reading
them.
One immediately obvious theme is that the
language used by different authors is different
for what I assume to be the same
regolith materials. The most misused terms
are “laterite” and its derivatives, “ferricrete”
and “ferruginous duricrust” and “duricrust”. I
was never exactly sure what authors were
describing, nor how the terms used were
intended. The Regolith Glossary defines all
these terms clearly. It is unclear whether
authors are referring to a material or a profile
or to a hard cemented material or a loose
scattering of ferruginous materials over a
surface. Since ferruginous materials make up
a large part of the regolith in Australia
clarity on the use of words to describe it is
essential. After all, if we use the word basalt
other geologists have a clear picture of the
material to which we refer, “laterite” on the
other hand is a term which conveys different
meanings to different people.
Other terms that seem to be used differently
by various authors include “duricrust”,
“calcrete”, “surface” or “landsurface”, soil
TAG December 2006 | 39