Stonelayers (stone-lines) in Soils: A priori assumed to be basal parts of biomantles

1. Stonelayers (stone-lines) in Soils: A priori assumed to be basal parts of biomantles by D.L. Johnson,1, 2 C.L. Balek,2 and R.J. Schaetzl,3 1Department of Geography, University of Illinois, Urbana, IL, USA 2Archaeology and Geomorphology Services, 2220 Mayfair, Westchester, IL, USA 3Department of Geography, Michigan St. Univ., E. Lansing, MI, USA

2. Our purpose is to show that: • Stonelayers (stone-lines) are common in biomantles of soils that form in mixed clast gravelly materials in many environments on all continents -- except possibly Antarctica;

3. . . .and to show that: • On stable continental surfaces of the humid tropics and subtropics, biomantles are commonly meters thick, and their basal stonelayers commensurately meters deep. Here are some examples:

4. Humid Tropical Biomantles • Upper photo is in northern Misiones Province, Argentina. Arrow is pointing to basal stonelayer of soil formed in basalt. • Lower photo is in coastal Ivory Coast; top of stonelayer is at arrows.

5. . . . and also that: • In the midlatitudes biomantles are typically thinner, and their stonelayers commensurately shallower. Here are some examples:

6. Midlatitude Biomantles • Upper photo, soil formed in schist, coastal NSW, Aust; stonelayer at base of biomantle (arrow). • Lower photo, Carmel, CA; soil formed in Monterey Shale colluvium (arrow shows thickness of biomantle; 40 cm).

7. And to further show that, in the upper Midwest: • Biomantles with stonelayers occur on both the Des Moines Lobe and Iowan Surface of Iowa and MN. Here are some examples:

8. Des Moines Lobe & Iowan • Upper photo shows a minimalist biomantle on young, and deformed, Des Moines Lobe drift in Lyon Co., MN. • Lower photo shows a biomantle on the Iowan Surface, Roger Johnson Quarry, Dodge Co., MN.

9. And Also in the Upper Midwest: • Biomantles with stonelayers also occur in the upper part of the buried Sangamon soil (formed in Illinoisan drift), and in the buried Yarmouth-Sangamon soil (formed in pre-Illinoisan drift). Here is an example:

10. Buried Sangamon Biomantles • Iowa City Yarmouth- Sangamon Soil in pre-Illinoisan drift showing biomantle (A & E horizon plus stonelayer); note ‘ferretto zone’ (Bt) with stonelayer on top, at feet of figure (in bottom photo).

11. And Also in the Upper Midwest: • It is noteworthy that the reddish Bt horizon of these buried drift soils was early called the 'ferretto zone’, and -- most importantly -- the stonelayer was termed the 'pebble band’, ‘pebble concentrate’, and an erosional ‘pebble lag’. Note the geogenic assumption!

12. Based on These Observations, and Many Others, We Posit That: • Most of these worldwide and upper Midwest stonelayers, we submit, are pedogenic in origin, and are simply basal parts of biomantles. • Now, stonelayers that occur in non-soil contexts, for example in glacio-fluvial sediments, are geogenic in origin, and are produced by erosional and depositional processes, or combination thereof. • But researchers in glaciated areas, where some stonelayers are geogenic, unfortunately transferred their conclusions to soils in general, and thus to soils in non-glacial areas the world over!

13. . . . And Also Posit That: • Biomechanical sorting by organisms was ignored as part of the soil forming process. • The coarse fraction stonelayer was historically ignored in soil genesis studies, and simply claimed to represent a ‘lithological discontinuity’. • Soil scientists/pedologists have over-focussed on the fine fraction because of yield considerations. • In the absence of biomantle theory, pedogenic and geogenic stonelayers were historically lumped together -- and simply assumed to be geogenic.

14. We Thus Conclude, That: • This has caused much interpretive confusion in Quaternary geology, climatic geomorphology, pedology, and in soil science. • Much literature therefore is compromised, but it cannot be erased! What can, or must, we do? • We can and must alert our students to the problem, and challenge them to formulate diagnostic criteria to differentiate geogenic from pedogenic stonelayers. • We offer a general truth as a firm step forward: stonelayers formed in soils are assumed a priori to be pedogenic in origin, and thus to be basal parts of biomantles.

15. Some clarifying definitions and conceptualizations:

16. We define soil as . . . . . . the outer layer, or ‘skin’, of substrates on planets and similar bodies altered by biological, chemical, and/or physical agents. The biomantle is the ‘epidermis’ of that skin and is produced largely (though of course not entirely) by bioturbation.

17. More formally, the biomantle is . . . . . . the epidermal part of Earth’s soil -- both subaerial and subaqueous soil. The biomantle is where most of Earth’s biota live, reproduce, metabolize -- use and expend energy, generate heat and waste, etc. -- and die, and where their remains accumulate upon death.

18. Dynamic denudation . . . . . . is a new framework that provides an entirely different view of landscape evolution. Its main focus is on biodynamics. The biodynamic pathways of pedogenesis consist of various complex biologically mediated processes that produce the biomantle. Biodynamic pathways coact with physico-chemical processes to produce soilscapes.

19. Biodynamics include . . . • Bioturbation, by many organisms at all scales. • Biologically mediated physico-chemical transformations, including biosynthetic productions, biogas, etc. • Bioaccumulations of living organisms and all non-living organic debris, biomass, exudates, pellets, etc. • Biovoid creation -- biopores, biochannels, biovugs-- that compose fenestrate, reticulate, ovate & inosculate biofabric. • Soil volume expansions that are produced by the sum of these processes, productions, and conditions.