626 E. M. KINDLE CANADIAN PLEISTOCENE CONCRETIONS 



forests would experience a small daily change in temperature, and ac- 

 cordingly small loss of water by evaporation, as compared with sections 

 exposed to the full glare of the sun where the banks are denuded of for- 

 ests. This complete exposure to the sun would mean relatively rapid 

 movement of ground-water toward the exposed section as a result of 

 evaporation and a consequent large transfer of the soluble materials 

 required. for the growth of concretions into the superficial vertical zone 

 represented by the face of the section. 



CONCRETIONS OF THE UPPER CLAYS 



In the silty clays which follow, the lower fine-textured marine clay 

 concretions are, at some localities, abundant. These beds afford concre- 

 tions quite unlike the claystones of the lower clays, but which are similar 

 to, if not identical with, the Norwegian forms called by Kjerulf** and 

 other Scandinavian geologists marleTcor. K distinctive term is needed 

 for these forms, and it is considered desirable to designate them by the 

 Scandinavian name marlelcor, which means fairy stones, a usage already 

 introduced by Quirke.*^ 



These concretions are characterized by a highly irregular or Avarty 

 surface and generally show no approach to any type of symmetry, a fea- 

 ture in which they contrast sharply with the concretions just described. 

 Instead of the usual smooth, more or less regular surface curvature of 

 the claystones from the lower clay, these forms show innumerable abrupt 

 irregularities in the surface, including pits and depressed groove-like 

 lines pursuing entirely erratic courses (plate 10, figures 2-5). The 

 spherical or subspherical type of concretion does not occur in association 

 with this t3^pe of concretion. These frequently show, on breaking, small 

 shrinkage cracks, which may or may not extend to the surface (plate 10, 

 figures 2 and 5). No example of these concretions is known showing a 

 shell or other organic nucleus. In size they range from the dimensions 

 of a pea to a man's fist. 



This type of concretion may be seen in the upper clays at various 

 localities. Specimens of these concretions occur sparingly in the road- 

 side cuttings in the clays about 2 miles south of Wilsons Corners, Que- 

 bec. They occur at various localities in the district and are abundant in 

 the lower portion of the brick-clay pits southwest of Billings Bridge. 



Their distribution in these clay pits is confined to the northern margin 

 of the lower pit in beds which are between 5 and 15 feet of the original 



Op. cit., pi. 5. 



T. T. Quiike : Can. Geol. Surv. Mem. 102, 1917. p. 56, pi. 5. 



