GEOLOGICAL AND MINERALOGICAL NOTES. 



No. 8. 



On a Pre-Glacial Sand Plain, probably of the 



Tertiary Age, in the Central Part of 



Essex County, Mass. 



BY JOHN H. SEARS. 

 (Curator of Geolog y and Mineralogy, Peabody Academy of Science, Salem.) 



Surrounding the drumlins or glacial hüls in Ipswich, 

 Rowleyand Newbury, can be seen deep beds of stratified, 

 nearly pure quartz sand that dip away at a slight angle 

 from the bases of the hüls ; they have been considered to 

 indicate ancient elevated sea-beaches. Tracing these sand 

 beds in a westerly direction they develop into a consider- 

 able sand piain covering a large part of the Linebrook 

 Parish in the western part of the town of Ipswich and ex- 

 tending to Great Swamp Brook in Rowley, forming the 

 piain known as Rooty Piain. Other large beds are seen 

 in WestNewbury, north of J. C. Peabody's hill and across 

 the town line into Georgetown. In this town it forms the 

 piain between Rock and Pentucket ponds and the south- 

 western part of Groveland, extending across West Box- 

 ford and a part of North Andover, largely in the Valley 

 occupied by the head waters or source of the Parker river. 



In North Andover there are a series of drumlins extend- 

 ing from the northeastern part of the town, in a nearly 

 southerly direction to Marble Ridge Station, that nearly 

 obliterate the sand piain except to the north of Great 

 pond and a portion of the Merrimac River bank ; here the 



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