692 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



Above a horizontal line the clays were horizontal and normal in every 

 respect; below this they were extremely contorted, as indicated in PI. XVI, 

 showing a smoothed surface about 4^ inches square. Where the contor- 

 tion was less pronounced, about 2 feet below the plane of disturbance, 

 in a layer with a thickness of 1 foot and a length of 15 feet, a beautiful 

 pressm-e cleavage was developed, superinduced upon the original lamina- 

 tion (PI. XVII) in the whole mass of the clays along parallel planes 2 to 

 4"" apart and dipping 32° N. Every stage in the series, from a slight, 

 sharp monoclinal fold affecting all the lamiure along a single plane to the 

 shearing off of the laminae by small parallel slip faults, could be followed, 

 and the clays, parting easily along the lamination and cleavage planes, 

 broke up into a mass of long pencils. 



The more marked fissures are about 6 to the inch ; between these again 

 are finer ones, making the whole number about 18 to the inch. Along 

 these the clay is very often slightly faulted; in one case the slip amounts 

 to an inch. The newly formed cleavage layers have undergone decided 

 compression and distortion, which is brought out clearly by the difference 

 in color of the upper and under portion of the original lamina?, so that in 

 tracing the dai'k bands across the several cleavage planes we find them 

 more or less separated into parts placed slightly en Echelon by the con- 

 tinued faulting in one direction, and these parts variously elongated and 

 flattened out parallel to the plane of cleavage. We may assume the jolane 

 of this incipient cleavage to be normal to the direction of pressure. A 

 second system of distant fault planes occurs at right angles to the first, 

 wliich are more distant from each other and have greater tlu'ow, showhig 

 that the parts of the bed slip^jed slightly on each other in the direction 

 of the pressure. 



The locality is 125 feet above sea, and thus somewhat lower than 

 the preceding section, but it lies out in the valley, where the clays did not 

 reach so great a height as on its borders, and the disturbance must have 

 been very nearly — I think it may be assumed to have been exactly — syn- 

 chronous with the last disturbance of the previous section. Its position 

 under the lee of a prominent hill, protected from icebergs and floe ice, 

 would also point to a continuous mass of glacial ice as the agent of its 

 formation. 



