254 



The nature of the lacustrine deposits is shown in the fol- 

 lowinsf section : — 



Fig. 1. 



(a) High-level gravel of creek, 12 ft. 

 (h) Surface soil, 6 in. 



(c) Good clay, 6 in. 



(d) Calcareous clay, 3 ft. 6 in. 



(e) Strong marly clay (makes excellent puddle), contained 



bones of marsupials near the bottom, 20 ft. 



(fj Chara beds. Fine to coarse sand and clay mixed with 

 the matted stems and fruits of Chara and decayed fresh- 

 water shells. Calcareous floors np to half an inch in 

 thickness consisting almost entirely of Chara remains, 

 8 ft. 



(g) Lower marly clay ; sometimes carries Chara horizons, 5 ft. 



(hj Bottom gravel, 1 ft. 



Total, 50 ft. 6 in. 



The present bed of the creek is only about 2 ft. below 

 the level of the old lake bottom, which indicates the amount 

 of erosion that the stream has accomplished at that spot 

 since the inauguration of the lacustrine conditions and re- 

 excavation of its aggraded material ; but the time covered by 

 these events must have been considerable. 



The order of events appears to have been as follows : — 



1. The corrasion of the rocks by the stream in estab- 



lishing the grade, prior to the formation of the 

 lake. 



2. By some means the stream was checked in its flow 



and the water was thrown back on its upper 

 course for nearly a mile. 



