No. 6.— The Sand Plains of Glacial Lake Sudbury. 
By JAMES WALTER GOLDTHWAIT. 
CONTENTS. 
Introduction . . . ane 
Conditions of qaiiage alge the 
263 
Other possible explanations . . 
The ice-dam theory . 
front of the retreating ice-sheet 265] Tilting in New England presumable 
Life history of a temporary ice- from other evidence . 
front lake ‘ 266 | The probable effects of tilting on 
Factors which control the stability temporary lake features : 
of ice-front lakes . 268 | Methods and results of levelling in 
Physiographic features which ane Lake Sudbury . 
water-planes in an ice-front lake 269] Water-planes slanting poutlie ed 
Sand plains, — their form and struc- seven feet per mile . : 
ture: 269 | Probable history of Lake Sudning 
Eskers 271| The stage of confluence 
Significance of sand. iging 271| The Morseville stage 
Importance of sand plains in south- The Weston stage 
ern New England . 273| The Cherry Brook stage 
Discordance of level of sand iia 273| The Hobbs Brook stage 
Glacial Lake Sudbury . 274 | Outlets of Lake Sudbury . 6 
Arrangement of sand plains in al Direction and rate of tilt is ques- 
joing, districts). 9. <6 275| tionable 
Expectation regarding the Take The theory of many inkelot 
Sudbury water-planes . 277) Summary oa ee 
The horizontal step scheme ap- Bibliography 
plied to Lake Sudbury . 279 | Explanation of plates . 
Introduction. 
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802 
AutHouGH sand plains have received much attention from geologists 
in New England, it is only of recent years that the grouping of these 
deltas and their relative altitudes have been studied in a detailed way, 
with the purpose of tracing the history of the ice-front lakes in which 
they were built. 
The work done by Professors Crosby and Grabau, 
and by Dr. Clapp, has shown the possibilities offered by such a study. 
During the academic year 1903-1904, as a graduate student under Prof. 
W. M. Davis of Harvard University, I undertook a study of the sand 
