Paleosols, geosols, etc - comment by Vance Holliday

Posted by Vance Holliday 07 Sen 1999 19:41:57


I enjoyed the flurry of discussion regarding soils, paleosols, geosols,
etc. stimulated by Roger Morrison's comments (6 June & 4 July 1999) and by
my short piece in Quaternary Perspectives (v.9, n.3). The latter was an
abbreviated version of a longer commentary circulated in response to the
definitions of paleosols and geosols proposed by the Working Group on
Definitions used in Paleopedology (PP Newsletter #14). I particularly
enjoyed seeing the varying opinions and perspectives from workers around
the world. My purpose in preparing the original comments and in writing the
discussion that follows is to try to introduce some logic, consistency, and
field utility into the use of our everyday terminology. I am also following
up on the suggestion by Dennis Dahms (15 June 1999) and Don Johnson (7 June
1999) to expand my comments. Some of what follows repeats comments
circulated in early 1998.
The issue here, contrary to some of the comments made in the discussions
of the past few months, is not one of old vs new terminology, but rather
one of developing a professional vocabulary that is both well defined and
practical to use. I argue that "paleosol" is neither and that "geosol" is
not practical and, moreover, current definitions and usage of these terms
does not represent "scientific progress." Whether or not soil
geomorphologists and soil stratigraphers believe in a steady state theory
of soil genesis is an interpretive and theoretical matter and not the issue
here. Our vocabulary should be independent of such concepts. A sandstone is
a sandstone, a formation is a formation, and a fossil horse is still a
fossil horse regardless of ones views of continental drift, plate
tectonics, and punctuated equilibrium. Likewise,
The terms we use should be defined as simply and clearly as possible so
they are easily applied in the field. Field work, after all, forms the
basis for our research into the history and evolution of landscapes and
related soils. If our terms are difficult to apply or difficult to define,
then what use are they? Definitions of "paleosol" vary widely and all are
impractical to use. These definitions include: soils of obvious antiquity
(Morrison, 1967:10); ancient soils (Butzer, 1971:170); soils formed on a
landscape of the past (Ruhe, 1965:755: Yaalon, 1971:29) or under an
environment of the past (Yaalon, 1983); and as soils formed under
conditions generally different from those of today (Plaisance and Cailleux,
1981:702). See also the recent discussions by Follmer (1998:1), Bronger and
Catt (1998), and Johnson (1998). In these definitions, exactly what
constitutes a pre-existing or past landscape or past environment or how old
the soil has to be was never defined. As noted by Johnson (1998), because
landscapes always are being subjected to some modification and the
environment is never static, and because all soils take some time to form,
it could be argued that all soils are paleosols and all unburied soils are
relict soils, making such terms redundant. In any event, data on past
landscapes and past environments are not always easy to come by and genetic
interpretations can remain contentious.
More broadly, there is no fundamental reason to differentiate soils based
on their relevance to the past or present if we follow some of the
fundamental rules of geologic nomenclature (which seems to be what we are
trying to do). In geology a gravel layer is a gravel whether it was
deposited in this century or in the Permian. If the gravel is lithified
then it is a conglomerate, but otherwise no distinction is necessary.
Likewise, plant and animal remains may be identified as fossilized but
otherwise they are identified and named according to principals of
biological classification with no indication made to whether they are
living or extinct.
The definition of paleosol proposed in PP Newsletter #14 is an attempt to
provide an unambiguous definition based on age by establishing the
somewhat arbitrary criteria of pedogenesis in the Pleistocene or earlier
geologic periods. This creates a situation similar to that for
classification in the U.S. Soil Taxonomy: considerable information must be
assembled before the term can be applied. In the case of the new definition
of paleosol, data on the age of the soil and its genetic evolution must be
available before a field scientist can know whether to properly call the
zone in question a soil, a paleosol, or a buried soil. This seems illogical
and is clearly impractical for field workers.
The term geosol has a more straightforward definition but as with
"paleosol" its utility is questionable. In the case of geosol a soil has to
be buried. This creates a situation where a clearly traceable soil that is
locally buried or locally exposed can be a geosol in some places but not
others. This seems illogical and clearly is impractical for many of us.
>From the time it was proposed (by Morrison in 1967) until its adoption in
the Code in 1983, it was seldom applied, clearly indicating that it lacked
real utility or that it was not in fact superior to soil as a formal
pedostratigraphic term. Even since 1983 it has not been widely used in the
stratigraphic literature.
I agree that we need a formal stratigraphic nomenclature for soils and
have never argued against this issue. But I see no reason why the term
"soil" cannot be used in place of "paleosol" or why soil-stratigraphic
units cannot be formal termed "Soils" (e.g., the Sangamon Soil). Morrison
(4 July 1999 an in various publications) argues that "soil " was rejected
as the term used for a formal pedostratigraphic unit by the American
Commission on stratigraphic Nomenclature because it was "highly ambiguous."
Follmer (14 June 1999) argues that "the word soil has too many meanings
and applications for good science." I counter that there is more agreement
among us (including both geologists and soils scientists) on the definition
of "soil" than there is on the definition of "paleosol"! In any case, what
is the point of replacing one term that might be ambiguous with a term that
is clearly ambiguous? This is not a sign of a "progressive scientific
community." The argument that the definition of "soil" varies among
"engineers, farmers and laundresses" simply is irrelevant and certainly of
no concern to soil- geomorphologists, soil stratigraphers, and pedologists.
I strongly agree with Kieth Crook's (17 June 1999) comment that the
definition of paleosol, if we continue to use is, should be applicable to
both Quaternary and older soils. I propose that paleosol be applied to
soils that are lithified. In geology, a sand is a sand, for example,
regardless of age or stratigraphic position. We do not call a Pleistocene
or older sand or a sand associated with a past landscape a "paleosand." If
a sand is lithified, however, we call the deposit a sandstone. Why can't
this same, common sense approach be applied to soils? i.e., define a
paleosol as any soil that is lithified. The concept is generally easy to
apply in the field upon visual examination, and requires no data on
numerical age control. Soil and buried soilcan be applied to soils that are
not paleosols.
Morrison (6 June 1999) argues that by the definition I propose, all
Quaternary soils and many Tertiary-age soils could no longer be termed
paleosols. So what? Is the point here that we come up with definitions that
fit our preconceptions or are we trying to develop definitions that are
unambiguous and logical? Shouldn't we be working toward a common vocabulary
with clear, straightforward definitions? That is all I am trying to do.

Bronger, A., and J. A. Catt, 1998. Summary outline and recommendations on
paleopedological issue. Quaternary International, v. 51/52, p. 5-6.

Butzer, K. W., 1971. Environment and archaeology (2nd ed.): Chicago,
Aldine, 703 p.

Follmer, L. R, 1998. Preface. Quaternary International, v. 51/52, p. 1-3.

Johnson, D. L., 1998. Paleosols are buried soils. Quaternary International,
v. 51/52, p. 7.

Morrison, R. B., 1967. Principals of Quaternary soil stratigraphy; in
Quaternary Soils, eds. R.B. Morrison and H.E. Wright: Reno, Desert Research
Institute, University of Nevada, p. 1- 69.

Plaisance, G. and Cailleux, A., 1981. Dictionary of soils: New Delhi,
Amerind Publishing Co., 1109 p.

Ruhe, R. V., 1965. Quaternary paleopedology; in The Quaternary of the
United States, eds. H.E. Wright and D.G. Frey: Princeton, New Jersey,
Princeton University Press, p. 755-764.

Yaalon, D. H., 1971. Soil-forming processes in time and space, in
Paleopedology, ed. D.H. Yaalon: Jerusalem, University of Israel Press, p.
29-40.

Yaalon, D. H., 1983. Climate, time and soil development; in Pedogenesis and
Soil Taxonomy, part 1, Concepts and Interactions, eds. L.P. Wilding, N.E.
Smeck, and G.F. Hall: Amsterdam, Elsevier, Developments in Soil Science
11A, p. 233-251.