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.