



I 



THE 



AMERICAN JOURNALOFSCIENCE 



[FOURTH SERIES.] 



Art. I. — Factors in Movements of the Strand Line and 

 their Results in the Pleistocene an d*Post- Pleistocene ;* by 

 Joseph Barbell, New Haven, Connecticut, including a 

 letter on Botanical Evidences by M. L. Fernald, Cambridge, 

 Massachusetts. 



Table of Contents. 



Introduction 1 



The interpretation of composite rhjthms 3 



Indications of oscillations given by subaqueous proxies 4 



Pliocene and Pleistocene marine terraces 9 



Post-glacial emergent cycle marginal to the glaciated areas 18 



Botanical evidences by M. L. Fernald 17 



Possible effects of radial shrinkage 20 



Conclusion 21 



Introduction. 



The problems of the nature of the Pleistocene and post- 

 Pleistocene movements of the strand lines and their causes are 

 important from a number of standpoints. They constitute one 

 of those common fields in which stratigraphy and physical 

 geology meet. The evidence shows a complex series of move- 

 ments, indicating a complexity of causes. Each locality may 

 give indications of the existence in the recent geologic past of 

 both higher and lower stands of the sea, recorded by such 

 unlike features as elevated seaplains and cliffs, on the one 

 hand, by drowned river valleys on the other. Minor rhythms 

 of movement are superposed upon larger rhythms. What is 

 the proper sequence, what the relative duration, and what the 

 correlation of successive stages of emergence and submergence 

 between different localities? As the last phase in this series 

 of oscillations, what is the direction and amount in different 

 regions of the last movement of the strand line ? 



* Written at the suggestion of Dr. T. Wayland Vaughan and presented 

 with lantern slides at the meeting of the Geologioal Society of Washington , 

 on March 24, 1915. 



Am. Jour. Sci. — Fourth Series, Vol. XL, No. 235.— July, 1915. 

 1 



