W. A. Johnston — Calcareous Sandstone. 449 



most of the time. At certain stages of the river, particu- 

 larly during the times intermediate between high and low- 

 water stages of the river, there are daily oscillations of 

 sea-water and river-water over the banks, because of the 

 tides. During the greater part of the year, therefore, 

 the sand banks are saturated with sea-water and during 

 the freshet months they are saturated wdth river-water. 

 The river-water during the freshet is 2 to 4 degrees C. 

 warmer than the sea-water. The temperature of the 

 river-water during the fresliet months varies from 12 

 degrees C. in May to 18 degrees C. in July or August. 

 The temperature of the surface sea-water in the Strait 

 of Georgia, near the mouth of the river, varies from 12 

 to 14 degrees C. ; at a depth of 25 feet it is 10 to 11 degrees 

 C. and at depths of 50 to 100 feet, 9 to 10 degrees C. 



Tlie mode of formation of the calcareous material as 

 suggested by the mode of occurrence and the conditions 

 under which it occurs is as follows : The lime which forms 

 a considerable part of the material is probably derived 

 from the shells, for the shells are partly dissolved, they 

 usually form part of the material, and the river-water 

 does not contain an excess of lime, the average of 22 

 analyses made by the Department of Mines showing- 

 only 11.85 parts per million of calcium. The analyses 

 w^ere made from composite samples of the river-water 

 taken tri-weekly at New Westminster for the period of 

 one year from May 5, 1919, to May 5, 1920. The sea- 

 water, which contains much less lime than the river-water 

 and is probably rendered acid by the gas formed from the 

 decay of the wood, tends to dissolve the shells. The 

 river-water, which displaces or mixes with the sea-water 

 in the sand banks, tends to cause deposition of the bicar- 

 bonate of lime in solution because of the higher tempera- 

 ture and higher lime content of the river-water. The 

 shells are partly aragonitic in character and hence are 

 readily dissolved. The lime is deposited as calcium car- 

 bonate and is not readily redissolved. There is thus a 

 mass actioji in the direction of deposition of the lime. 



The occurrence is an unusual one and differs from the 

 well-known ^ ^ stone or rock reefs ' ' in that the material is 

 formed below the permanent water level. It shows that, 

 in exceptional circumstances such as obtain in the seaward 

 part of the Fraser delta, lithification, to some extent, of 

 the sediments and the formation of sandy and shelly 

 limestone and concretionary limestone may take place 

 below the permanent water level. 



