GEOLOGY OF PLAIN VILLE 



451 



Blake Hill fault-block, with southwestward dipping Carboniferous beds, un- 

 cleaved, unmetamorphosed. 



Vertical beds of Carboniferous series in Plainville valley and the ridge east of the 

 town, slaty in structure. 



Figure 1. — Geologic Map of the Vicinity of Plainville, Massachusetts. 



1. Footprint locality, shales overlain by gray sandstone, much jointed, dipping gently southward. 



2. Vertical shales, sandstones, and grits. ■ 



3. Two parallel vertical ledges of alternating slates and slaty sandstones. 



4. Highly inclined curved ledges of sandstones and slates. 



5. Quarry, sandstones with shaly layers, varying westerly dips ; raindrop imprints, Asterophyllites. 



6. Shales and sandy shales, gentle southwest dip ; raindrop imprints. 



7. Southwestward dipping ledge, traceable to the southeast, conglomerates, sandstones, and shales. 



8. Strong ridge of conglomerates and sandstone, with shale layers. 



9. Vertical slates, with gray sandstones. 

 10. Vertical slates. 



Dotted line shows approximate trace of thrust-plane along which the vertical beds disappear 

 beneath the fault-block. 



BLAKE HILL FAULT-BLOCK 



This block of strata forms the western wall of Plainville valley, the 

 floor of which is composed of the vertical Carboniferous beds shown on 

 the map, figure 1. The trace of the thrust-plane on the surface is clearly 

 indicated by the distribution of outcrops. The footprints occur in shales* 

 at the bottom of the block west of the Plainville railroad station and on 

 the south side of the street at the locality marked number 1 on the map. 



c 



