The History of INQUA- for XX INQUA Congress

Many years ago there was talk about the preparation of a detailed history of INQUA (the International Union for Quaternary Research) but nothing seems to be happening; no materials are appearing. In the interim, and in time for the XX INQUA Congress in Dublin in 2019, here is a link to a short history of INQUA- available online thanks to Michigan State University.

Notes for a history of INQUA- the International Union for Quaternary Research (Association pour l'etude du Quaternaire, Internationale Quartarvereinigung, etc.  2011. Ian Smalley. Loess Letter 65 (ISSN 0110-7658) online at www.loessletter.msu.edu

The INQUA Loess Commission provided additional historical data and the doings of that particular Commission are fairly well recorded:

Smalley, I.J., Markovic, S.B., O'Hara-Dhand, K. 2010.  The INQUA Loess Commission as a Central European enterprise. Central European Journal of Geosciences/ Open Geosciences 2, 3-8.

Smalley, I.J., O'Hara-Dhand, K. 2010.  The Western Pacific Working Group of the INQUA Loess Commission: expansion from Central Europe. Central European Journal of Geosciences/ Open Geosciences 2, 9-14.

Smalley, I.J., Howarth, J., Nugent, H.  2011.  The INQUA Loess Commission goes from Budapest to Beijing, and then returns to Europe (1991-2003).  upload to Scribd.com

 

Fragipans & Loess [part 2]

Loess & fragipans: Development of polygonal-crack-network structures in fragipan horizons in loess ground.  I.J.Smalley, S.P.Bentley, S.B.Markovic 2016.  Quaternary International 399, 228-233

What have we here?  This highly speculative figure purports to show possible contacts in an ideal loess soil. Some of these contacts allow collapse, some are less collapsible. Collapse does seem to be a key aspect of fragipan formation. Deformation processes play a role in fragipan formation in various ways (a) initial collapse (b) shrinkage causing the development of a polygonal crack network (which is a defining aspect of Fragipans in Soil Taxonomy).

 Fragibutt structures in the coastal Fragic Pallic Soils; SI NZ. This exposure is at Normanby, near Timaru. The figure comes from: Berger, G.W., Pillans, B.J., Tonkin, P.J.  2001.  Luminescence chronology of loess-aleosol sequences from Canterbury, South Island, New Zealand.  New Zealand J. Geology & Geophysics 44, 501-516. Scale bar 10cm.

 Fragic Pallic Soils;  South Island New Zealand. 

Fragipans in Loess

A fragipan is a soil horizon (often Bx).  Fragipans form in silty soils, they form in loess- in fact one wonders if the fragipan in the loess is the true fragipan and all others are in some way faux fragipans. The reason for this statement is that loess is the system that starts out with a low packing density- and acquiring a higher packing density appears to be a requirement for fragipan formation.

Look at this fig. of fragipans in the USA- this is from Bockheim & Hartemink (Catena 104, 233-242, 2013)  the fragipans favour the east, where rainfall is higher- needs to exceed evapotranspiration for efficient fragipan formation. Loess country is highlighted.
There is said to be a continuing discussion about the mode of fpan formation. Two angles are explored (a) the physical angle- which requires the necessary densification to be produced by hydroconsolidation, and (b) which requires fpan properties to develop chemically, movements of ions and substances in the soil system are involved.
There appears to be macro-movement in the fragipan system. Movement of silt sized particles is involved, first to collapse to the required density, and then to respond to drying forces and develop the characteristic prismatic structure. There does not seem to be any chemical explanation for the formation of the prismatic structure (noted by John Hardcastle in the first description of fragipans in 1890). Look at the sketch by Van Vliet & Langohr (reproduced by Smalley Bentley Markovic 2016 QI 399, 228-233):

this shows the prismatic structure rather nicely. When the system collapsed there is excess water (pore volume has decreased) as water leaves contraction stresses develop and characteristic polygonal crack pattern ensues.
It is possible that the fragipan discussion is now in a situation that the loess discussion used to be in. Once upon a time there were two approaches to loess deposit formation (a) physical- the material was brought by wind and deposited to form an open packing, and (b) chemical- the classic Bergian in-situ idea where loess formed by weathering and soil formation processes; by the movement of chemicals. Now- bits of the Berg idea remain and are useful and have been incorporated into modern loess lore but nobody denies that loess deposit formation is an aeolian event- and that this aeolian event delivers many of the defining properties. Moving silt sized primary mineral particles is critical for loess deposit formation. Moving silt sized primary mineral particles might be critical for fragipan formation- the chemistry may be interesting but incidental. The major properties of fragipans could be explained by structural collapse via hydroconsolidation, and prismatic structure formation via drying stresses.
The ideas appear to fit a loess system; what about non-loess fragipans?. Perhaps there are no non-loess fragipans- just fragipan-like horizons? 

Examine the map of fragipans in Eurasia- some interesting looking occurrences in NW Italy- but not a lot of fragipan records.

Sketch from thesis by G.L.Scott University of Canterbury 1979 showing fragipan situation in the loess at Banks Peninsula. The fragipan relates well to the surface; the sketch offers good support for the Bryant hypothesis of fragipan formation.