EXPLANATION OF DIAGRAMMATIC SUMMARY 



431 



Explanation of Figure 2 



Conventions used in diagram. — Time 

 is represented in sequence from left 

 to right. As the total lapse of ages 

 represented by the record is un- 

 known and the relative durations 

 of successive ages are indeterm- 

 inate, there is no definite time 

 scale ; but that portion of pre- 

 Franciscan time represented was 

 probably much longer than post- 

 Franciscan time. The time scale 

 is therefore much smaller at the left 

 than at the right of the diagram. 



Vertical ordi nates represent posi- 

 tions in the earth's superficial crust 

 from a mile above sealevel to 6 miles 

 below sealevel. Sealevel is arbitra- 

 rily taken as a fixed datum. 



/Sequence of sea and land. — The 

 upper curve represents from age to 

 age the varying relation of the rock 

 surface to sealevel in the chosen 

 locality. Below T sealevel the posi- 

 tion of this line results from the 

 amount of subsidence, less the 

 thickness of deposits. Above sea- 

 level its position is determined by 

 the amount of uplift, less the effect 

 of erosion. The values indicated 

 are to be taken qualitatively, not 

 quantitatively. The following is 

 the interpretation of the several 

 lettered sections : 



a-b. Submergence; sedimentation 

 corresponding to the strata 

 of the Coast complex; com- 

 prising epochs probably of 

 great duration and of com- 

 plex physical changes; 

 probably closed by orogenic 

 movements that resulted in 

 folding of the Coast com- 

 plex in the zone of defor- 

 mation by flow, and were 

 connected with granitic in- 

 trusions. 



3 2 



^ 



c ® 



O o 



o a, 



a o 



o c 



5 H 



•5" ^ 



o 



W " 



— o 



<< CD 



Present 



