620 ' E. M. KINDLE CANADIAN rLEISTOCENE CONCRETIONS 



seen in place, but some were found in the clay. The clay oozes or creeps down 

 to the creek and is here washed, leaving a placer of concretions. 



''The concretions have commonly one flat side and a side opposite to it with 

 a convex curvature. In some instances the flat side is uppermost ; in other 

 cases it is down. The greatest diameter of the flat concretions is parallel to 

 the strata. Concretions with a vertical length exceeding the transverse length 

 consists of superposed disks which lie parallel to the strata. Sandy beds seem 

 to be the most favorable for concretions. The flat side of the concretions lies 

 in a thin layer of sand and the convex side is in clay or sandy clay. This was 

 observed in several places. 



''Quite a number of beds in a clayey bank contain concretions, but they are 

 concentrated along certain beds and are not scattered promiscuously through- 

 out the clay. A plane 1 foot square along a concretion-bearing bed might have 

 half its area occupied by concretions. A vertical plane 1 foot square might 

 cut concretions only in a certain bed. Further, the concretions are concen- 

 trated in areas along any particular conpretion-bearing bed. An area of 50 

 square feet along a concretion-bearing bed might contain 2.5 square feet of 

 irregular concretions. An adjacent area of the same size along the same bed 

 might contain only a few square inches of concretion per square foot of area." 



The contrasts noted by Doctor Hanson in the shape of the concretions 

 found at the four localities mentioned probably correspond to lithologic 

 differences in the clays at slightly different levels. 



Ottawa Valley Concretions 



GEXEEAL STATEAIEXT 



The Pleistocene concretions from the lower clays in the Ottawa and 

 Saint Lawrence valleys differ from those of the Connecticut Valley, 

 which are barren, in inclosing fossils very frequently. This has caused 

 the Greens Creek concretions, which have been briefly described by 

 Weston,^'^ to become rather widely known. Dawson^^ has described and 

 listed many of their fossils and incidentally referred to the inclosinsf 

 nodules. Dr. 11. ^I. Ami has collected from these concretions a consider- 

 able fauna, including insects and plants as well as the common inverte- 

 brates. Johnson^^ has discussed one of the types of concretions found in 

 the Ottawa Valley Pleistocene clays. 



Pleistocene deposits in the Ottawa Valley have a vertical range of 

 about 600 feet, according to Johnson.^*^ The basal 100 feet, however, lie 

 below the level of the Ottawa River, so that nothing is known of the con- 



*' T. C. Weston : Notes on concretions found in Canadian rocks. Trans. Nova Scotian 

 Inst, of Sci., vol. ix. pp. 1-0, session 1S94-189.~>. 



^^ .J. W. Dawson : The Canadian ice age, 1S9G. pp. 266-267. 



*' W. A. Johnson : Pleistocene and recent depo.sits in the vicinity of Ottawa. Mem. 

 Can. Ceol. Surv.. no. 101, 1917. p. 29. 



**0p. cit., p. 20. 



