geological map 479 



Description of the Map 



Plate 43 is drawn to represent the regions specially described in this 

 paper. Owing to the small scale, many of the names mentioned, the 

 roads, and other details are not given. The order of the formations 

 given in the legend, with the exception of the igneous rocks, is from 

 below upward. The Lisbon-Swiftwater complex extends centrally 

 through the area, occupying the valley of the Ammonoosuc river. In 

 earlier maps the area in the eastern part of Littleton and a narrow strip 

 adjacent to the granite through the township was referred to the stauro- 

 lite mica schist group, of which there still seem to be a few relics, and 

 much more has apparently been absorbed by the Bethlehem granite 

 (page 465). The blank space in Lyman and Littleton is mostly occupied 

 by the Lisbon rocks, and the west line of Lyman coincides with the 

 Gardner range, averaging 2,000 feet of altitude. In the north part of 

 Bethlehem the vacant space eating into the granite represents till. 

 Farther south the granite itself might have been represented. The blank 

 space to the southeast of the schists in Lisbon and Landaffis chiefly gneiss. 

 There is also a large vacant space indicate g till near Streeter pond. 

 The scale proves inadequate to show satisfactorily the distribution of 

 the auriferous conglomerates in Bath and Lyman; nor is the coarse 

 conglomerate which merges into the argillitic schists to the north on 

 Youngs pond and west of Mormon hill represented. Only one section, 

 the most general one (figure 8, plate 42), is indicated. To have inserted 

 the others would have obscured important details. 



Conclusions 



This paper may be regarded as a report of progress. The relations of 

 the several formations are better understood than ever before, but much 

 remains to be elucidated. It is desirable to place on record what seems 

 to be established, to serve as a guide for later studies. 



1. It is clearly established that there is a horizon of middle Upper 

 Silurian age in the limestones of the Blueberry Mountain area. 



2. In a direct upward stratigraphical succession above the limestone 

 there are a sandstone, an argillite, coarse conglomerate, dark and drab 

 slates. There are no fossils to decide whether any of these strata are 

 newer than Upper Silurian, but the varied succession and the consid- 

 erable thickness suggest the presence of some Devonian. 



3. There is equal uncertainty as to the exact place of the supposed 

 inferior schistose complex and the argillitic schists. At present the 

 general term of Lower Silurian (Ordovician) may be applicable. 



4. A long list of what were formerly called metamorphic schists may 

 now be classed as eruptive igneous rocks, such as the porphyritic gran- 



