Value of 'paleosol'

Posted by David Lowe 21 Jun 1999 03:34:36

Dear colleagues,

I have been following the email discussion about the relevance and
importance of terms such as 'geosols', 'paleosols' etc with interest. My
new zealand perspective is similar to that of Dr Crook of Australia - the
word 'paleosol' is used quite frequently, 'geosol', although acknowledged,
is not used much at all (nor is 'pedoderm' for that matter). I find
'paleosol' to be a useful and well-recognised term as is paleopedology.
Some Quaternarists in New Zealand use 'buried soil' instead of buried
paleosol and the distinction is one of preference in the end (e.g Almond
1996). My personal preference is for paleosol - it is a well established
term used by pedologists and (importantly) geoscientists alike, and because
many (most?) buried soils we deal with are truncated/incomplete (Bw or Bt-C
horizons) profiles/pedons and so don't always resemble a modern soil pedon.
I use the simple definition of a paleosol as a soil of a past landscape or
environment, and have no problem in separating buried paleosols, non-buried
paleosols, and exhumed paleosols. All of these occur in New Zealand. An
important distinction made is that paleo means old in the sense of past,
not necessarily a 'long time'. For example, the soil/landsurface buried by
Tarawera Tephra on 10 June 1886 following the Tarwera eruption has become a
paleosol but it is now only a little over 100 years old and so is hardly
'old' in a geological sense. On 11 June 1886 it was a paleosol aged 1 day.
In contrast we have some paleosols developed in tephras that are over 2 Ma
(e.g. Lowe, 1994).

Another important aspect of paleoedology in New Zealand is the recognition
of the accumulatory nature of many landsurfaces in both volcanic and
loessic terrains - either paroxysmally and incrementally - so that
multisequal soils are common. I emphasise in volcanic (tephra) terrains to
students the interplay between surface upbuilding as tephras are added to
the surface (typically only a few mm or cm in thickness e.g. Lowe 1986;
Hodder et al. 1990) and 'top down' soil formation (horizon developent). I
follow the models developed by Johnson et al. 1990 on dynamic pedogenesis
and soil 'evolution' (e.g. Bakker et al. 1996). Phil Tonkin and Peter
Almond in Lincoln in particular have emphasised this multisequal aspect of
many soils in NZ, especially in loesses (e.g. Tonkin et al. 1998).

The use of paleosols in stratigraphic contexts is widespread and in fact
has been a major focus of Quaternary research in New Zealand. But much of
the work relies on sequences of deposits rather than an individually
occurring single paleosols. A major development in recent years has been
the assigning of marine oxygen isoptope stage numbers to such terrestrial
sequences using a variety of techniques establish both linkages (e.g. by
tephrochronology and/or direct dating such as TL, paleomagnetism, AAR)and
paleoenvironments by proxy measures (e.g. quartz influx, P and K content,
mag susceptibility, grain size etc., e.g. Alloway et al., 1992a, b). The
role of buried paleosols in such sequences is essential as indicators of
interstadial or interglacial conditions (e.g. see model developed in Palmer
and Pillans 1996)and as stratigraphic markers. Recently Newnham et al. (in
press) reviewed Quaternary environmental changes in New Zealand and they
included a section on 'Paleosols' in the review.

Also, paleosols - sometimes represented by simply weak weathering only
(thin Bw horizon formation tha represent a few decades or centuries of
time)- are helpful in establishing volcanic history as for example in the
seminal work by Wilson (1993) on the Taupo volcano.

In conclusion, I would suggest that the term 'paleosol' is here to stay and
that it is a very useful term that is widely used in both pedology and
geosciences. I favour the simple definition as given above and do not go
along with suggestions to restrict it to lithified deposits or whatever.
The 'weakest' application is undoubtedly where the term relates to
'surface' or 'non-buried' paleosols because these soils are clearly in the
'modern' environment but may contain relict features. Separation of relict
vs. modern features in such pedons is open to question and interpretation
and Johnson et al. made the valid point that 'all soils to some extent are
paleosols'. In the end I think the purpose of any paper or research project
must dictate the terminology and so long as that is well defined as needed
then there should not be any problem in communication.

Best wishes for a successful meeting in Durban.

References
Alloway, B.V., McGlone, M.S., Neall, V.E. and Vucetich, C.G. 1992. The role
of Egmont-sourced tephra in evaluating the paleoclimatic correspondence
between the bio- and soil-stratigraphic records of central Taranaki, New
Zealand. Quaternary International 13-14, 187-194.

Alloway, B.V., Stewart, R.B., Neall, V.E. and Vucetich, C.G. 1992. Climate
of the last glaciation in New Zealand based on aerosolic quartz influx in
an andesitic terrain. Quaternary Research 38, 170-179.

Almond, P.C. 1996.Loess, soil stratigraphy and Aokautere Ash on Late
Pleistocene surfaces in south Westland, New Zealand: interpretation and
correaltion with glacial stratigraphy. Quaternary International 34-36,
163-176.

Bakker, L.; Lowe, D.J.; Jongmans, A.G. 1996. A micromorphological study of
pedogenic processes in an evolutionary soil sequence formed on Late
Quaternary rhyolitic tephra deposits, North Island, New Zealand. Quaternary
International 34-36: 249-261.

Hodder, A.P.W.; Green, B.E.; Lowe, D.J. 1990. A two-stage model for the
formation of clay minerals from tephra-derived volcanic glass. Clay
minerals 25: 313-327.

Johnson, D.L., Keller, E.A., Rockwell, T.K. 1990. Dunamic pedogenesis and
some key soil concepts, and a model for interpreting Quaternary soils.
Quaternary Research 33, 306-319.

Lowe, D.J. 1986. Controls on the rates of weathering and clay mineral
genesis in airfall tephras: a review and New Zealand case study. In:
Colman, S.M.; Dethier, D.P. (ed) Rates of Chemical Weathering of Rocks and
Minerals. Orlando, Academic Press: 265-330.

Lowe, D.J. (Editor) 1994. Conference Tour Guides. International Inter-INQUA
Field Conference and Workshop on Tephrochronology, Loess, and
Paleopedology, University of Waikato, Hamilton, New Zealand. 186pp.

Newnham, R.M., Lowe, D.J. and Williams, P.W. 1999. Quaternary environmental
change in New Zealand: a review. Progress in Physical Geography (in press)

Palmer, A.S. and Pillans, B.J. 1996. Record of climatic fluctuations from
c. 500 ka loess deposits and paleosols near Wanganui, New Zealand.
Quaternary International 34-36, 155-162.

Tonkin, P.J., Almond, P.S., Alloway, B.V., Trangmar, B.B. and Palmer, A.S.
1998. The recognition and interpretation of aggradational and multisequal
soils from different depositional environments: some New Zealand examples.
Quaternary International 51-52, 47.

Wilson, C. J. N. 1993. Stratigraphy, chronology, styles and dynamics of
late Quaternary eruptions from Taupo volcano, New Zealand. Philosopical
Transactions of the Royal Society London A343, 205-306.
Dr David J. Lowe
Associate Professor
Department of Earth Sciences
University of Waikato, Private Bag 3105
Hillcrest Rd, Hamilton
NEW ZEALAND 2001

Work Ph + 64 7 856-2889 (ext. 8238)
Work Fax + 64 7 856-0115
Home Ph + 64 7 855-0692
Email d.lowe@waikato.ac.nz