ANCIENT SHORES, BOULDER PAVEMENTS, AND HIGH- 

 LEVEL GRAVEL DEPOSITS IN THE REGION OF THE 

 GREAT LAKES. 



BY PROF. J. W. SPENCER, M. A., PH. D., F. G. S. (l. & A.), 

 STATE GEOLOGIST OF GEORGIA. 



Chapter I. 

 Characteristics of Ancient Shore-lines in the Eegion of the Great Lakes. 



The land features throughout the lake region drained by the St. Lawrence 

 river owe their formation largely to the action of waves, sculpturing rocky 

 or modeling earthy shores. That the waves have not always been confined 

 to the margins of the modern lakes is seen in the sea-cliffs and beaches, from 

 which the waters have loug since receded. These features, still remaining, 

 are sometimes in the form of bold relief, and sometimes in the form of narrow 

 sand or gravel ridges, delicately traced over a flat country. In some places 

 these ridges approach near to the lakes ; in other localities they are miles 

 away, and at varying altitudes up to hundreds of feet above their present 

 waters. 



The raised shore-lines are no longer water levels, for terrestrial move- 

 ments, since the lakes have receded from them, have commonly lifted 

 them up to unequal altitudes. Whilst some of these old shores represent 

 former lake boundaries, there seems to be little reason to doubt that the 

 higher sea-cliffs and beaches formed the coast of brackish water inlets or arms 

 of the sea. 



Besides the deformation arising from the unequal terrestrial movements, 

 the shores have been in many places defaced by the action of rains, rills, 

 rivers, and landslides, until their broken continuity renders them somewhat 

 difficult to follow over long distances. The object of this chapter is to 

 describe the characters of the old raised and deformed water-margins, by 

 which they can be identified. The ancient coast-lines differ in no respect 

 from the modern, but they are often easier to follow, as there are no waters 

 to restrict one's footsteps. Were the lakes to be suddenly drained, but a few 

 years would elapse before the deserted margins would be as difficult to mark 

 out with precision as any of those from which the waters have long since 

 receded. 



With notable exceptions, the lakes are generally bounded by banks of 

 clay or sand, stratified or unstratified. The waves have in places cut into 



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