74 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



fTWENTY-THREE YEAR PERIODICITY OF 

 I VARVE THICKNESS 



CURVES (A-E) EACH IS MEAN OF 115 YEARS | 

 CURVE F (ON DOUBLE SCALE) MEAN OF 575 YEARS 

 YEARS 5 10 15 20 



Fig. 31. — Cycles of 2S years in Pleistocene varves. 

 Average results of 115-year intervals. 



