Response to Hari Eswaran's reply to V. Holliday
Posted by Leon Follmer 14 Sen 1999 19:15:27 Forward. This version replaces the first response to Hari Eswaran, which was not linked to his response. The format was changed to make the dialogue easier to follow. There are no changes in content. LF Response to Hari Eswaran [original is preceded by HE; response is preceded by LR] -----Original Message----- HE. I should stay away from this discussion as I am not a Paleosoilist, never was and never will be. I have never understood what 'age' that Paleosol specialists are referring to. Is it the age of the soil or the age of the soil surface? LF. Welcome Hari... Yes, either, depends on context. In stratigraphic context, age is the "calendar" age of the soil [surface] when buried. Conceptually, this is the "age" obtained when you radiocarbon date the buried soil [= buried paleosol]. Therefore in this context, age is the "date" of the soil. In contrast, the age of the soil in the sense of duration or maturity is a second meaning and is usually made in reference to modern "living" soils, although it is also applied to buried soils. When applied to buried soils, the duration age of the soil would need to be spelled out to avoid confusion with its stratigraphic age. LF. Challenge: I think paleopedology was noted first in Russia. The question: Yes, there are Quaternary and Tertiary soils -- in the same sense as Holocene [~modern] soils. It is the highest level of generalization of soils in a chronostratigraphic context. HE. In the few papers that I have read on the subject, Paleo-pedologists conveniently ignore geomorphic processes and their role in the development of the soil. By doing so, they miss an important factor in soil genesis. LF. Some do, some don't. Overall I think this is an unfair criticism. Working from cores or limited outcrops paleopedologists can't start with geomorphic information because it is not accessible to them. But, it is commonplace for geomorphic process ideas to be drawn into the interpretations to explain features that can not be explained by insitu processes. HE. If the soil we see today is a remnant of an older soil, what part of that older soil is it? On the other hand, if it is the truncated remains of an older soil, what processes (Including geomorphic) have contributed to its present properties? I always have difficulties in getting paleo-soil scientists to elaborate on these. LF. Good questions, I fully agree. Often one can see a spectrum of features in paleosols that must be the result different "ages" of formation. With careful study it is possible to establish the chronology of the features by applying basic principles -- superposition, cross cutting, alteration patterns, etc. dating these features is usually not possible, so the analyst is tempted to explain the history of these features by making up a story that is derived from his bias [experience or beliefs]... Also, in soil science, the simpler the story the better it is believed to be. HE. QUESTION: Why paleo-soil scientists do not elaborate on these issues? LF. This clearly reflects on the immaturity of the science. The complexity is simply too great to handle before confusion sets in. Therefore the "factors" must be simplified enough to handle. This has been a "politically correct" stance for years - as long as soil scientists have been overly satisfied with the "five factor" approach. It has always been amazing to me why soil scientists have been so satisfied with finding a model that can hold all the "pedo" parts but they do not know how to put them together into a meaningful "machine". In other words, the model comes with no "instructions" that explain where all the parts go, or even how "it should run". It is analogous to finding a bucket big enough to put all your metal parts in and having no guidance on how to assemble the "correct" machine or how it should run... There is little value in claiming all the "factors" are accounted for when glaring little [significant] relict pedo-features are ignored... Have you ever assembled a machine and have parts left over?.. There are many people who know about these things but we are in a world of babel right now and don't understand each other. A new improved model will come someday that will enable us to understand paleosol history better. HE. A final point that I have had difficulties with is, what is the need to invoke paleo conditions to explain the properties of the these soil; conversely, what properties do the soils have that cannot be attributed to recent processes? LF. Fair questions. The explanations depend on point of view. Often a rule of parsimony is applied, one that in general is most simple and seems to best fit the perceived circumstances. Also, there is a "basket syndrome" where if something does not fit the model then an exception is made. In other words, if it does not fit it must be relict [or in my experience I often hear "it must be geological if it can't be pedological"]. HE. We still have the task to rediscover the wheel. LF. [??] We have plenty of wheels but don't know much about the machine they belong to... Dr. Hari Eswaran Leon R. Follmer
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