﻿T. 
  N. 
  Dale— 
  Berkshire 
  Schist, 
  etc. 
  369 
  

  

  Aet. 
  XXVIII. 
  — 
  Local 
  Unconformity 
  between 
  the 
  Berk- 
  

   shire 
  Schist 
  and 
  the 
  Stockbridge 
  Limestone 
  in 
  Adams, 
  

   Mass.; 
  1 
  by 
  T. 
  Nelson 
  Dale. 
  

  

  In 
  the 
  course 
  of 
  the 
  tracing 
  of 
  hundreds 
  of 
  miles 
  of 
  

   boundary 
  between 
  the 
  Berkshire 
  schist 
  and 
  the 
  underly- 
  

   ing 
  Stockbridge 
  limestone 
  in 
  western 
  Massachusetts 
  and 
  

   western 
  Vermont 
  by 
  the 
  writer 
  and 
  his 
  former 
  assistants 
  

   a 
  number 
  of 
  immediate 
  contacts 
  between 
  these 
  forma- 
  

   tions 
  were 
  observed. 
  2 
  

  

  At 
  some 
  of 
  these 
  contacts 
  the 
  limestone, 
  generally 
  a 
  

   calcite 
  marble, 
  becomes 
  graphitic 
  within 
  a 
  few 
  feet 
  of 
  the 
  

   schist, 
  and 
  the 
  adjacent 
  schist 
  is 
  also 
  graphitic. 
  At 
  

   others, 
  however, 
  the 
  two 
  rocks 
  have 
  no 
  common 
  constit- 
  

   uent 
  and 
  their 
  relations 
  indicate 
  an 
  abrupt 
  change 
  from 
  

   calcareous 
  to 
  argillaceous 
  sedimentation. 
  

  

  While 
  working 
  on 
  the 
  geology 
  of 
  Mount 
  Greylock 
  in 
  

   1886 
  the 
  writer 
  in 
  bounding 
  the 
  small 
  schist 
  outlier, 
  a 
  

   mile 
  S.SW. 
  of 
  Adams, 
  and 
  due 
  W. 
  of 
  Maple 
  Grove 
  

   Station, 
  3 
  found 
  that 
  the 
  schist 
  within 
  a 
  few 
  feet 
  of 
  its 
  

   contact 
  with 
  the 
  marble 
  contained 
  what 
  appeared 
  to 
  be 
  

   pebbles 
  of 
  marble. 
  

  

  In 
  July 
  1919 
  while 
  running 
  the 
  boundaries 
  between 
  the 
  

   dolomitic 
  and 
  calcitic 
  limestone 
  of 
  the 
  Stockbridge 
  lime- 
  

   stone 
  for 
  a 
  forthcoming 
  U. 
  S. 
  Geol. 
  Survey 
  bulletin 
  for 
  

   the 
  benefit 
  of 
  the 
  lime 
  industry 
  the 
  writer 
  had 
  an 
  oppor- 
  

   tunity 
  of 
  revisiting 
  the 
  locality 
  and 
  obtained 
  the 
  follow- 
  

   ing 
  results. 
  

  

  The 
  marble 
  at 
  a 
  small 
  opening 
  about 
  200 
  ft. 
  E. 
  of 
  the 
  

   outlier 
  and 
  nearly 
  W. 
  of 
  the 
  station 
  is 
  so 
  micaceous 
  and 
  

   feldspathic 
  as 
  to 
  resemble 
  a 
  gneiss 
  and 
  has 
  been 
  used 
  for 
  

   curbing 
  and 
  even 
  for 
  construction. 
  Prof. 
  J. 
  E. 
  Wolff 
  

   described 
  the 
  stone 
  in 
  the 
  same 
  monograph 
  and 
  also 
  

   refers 
  to 
  similar 
  feldspars 
  in 
  an 
  earlier 
  publication. 
  4 
  

  

  The 
  marble 
  itself 
  has 
  an 
  average 
  grain 
  diameter 
  of 
  0-32 
  

   millim. 
  but 
  has 
  micaceous 
  laminae 
  0-1 
  inch 
  apart 
  which 
  in 
  

  

  1 
  Published 
  by 
  permission 
  of 
  the 
  Director 
  of 
  the 
  U. 
  S. 
  Geol. 
  Survey. 
  

  

  2 
  Some 
  of 
  the 
  more 
  accessible 
  of 
  these 
  in 
  Mass. 
  are 
  about 
  the 
  village 
  of 
  

   New 
  Ashford. 
  See 
  U. 
  S. 
  Geol. 
  Survey, 
  Mon. 
  23, 
  fig. 
  31, 
  p. 
  138; 
  fig. 
  32, 
  

   p. 
  139; 
  fig. 
  35, 
  p. 
  140, 
  1894. 
  

  

  3 
  Op. 
  cit., 
  PI. 
  I. 
  The 
  revised 
  boundary 
  makes 
  this 
  outlier 
  almost 
  5000 
  

   ft. 
  long 
  and 
  its 
  greatest 
  width 
  about 
  700 
  ft. 
  

  

  4 
  Wolff, 
  J. 
  E.: 
  The 
  geology 
  of 
  Hoosac 
  Mountain 
  and 
  adjacent 
  territory, 
  

   op. 
  cit., 
  p. 
  64. 
  , 
  Metamorphism 
  of 
  clastic 
  feldspar 
  in 
  conglomerate 
  schist, 
  

   Bull. 
  Mus. 
  Comp. 
  Zool., 
  Cambridge, 
  Mass., 
  vol. 
  16, 
  No. 
  10, 
  1891. 
  

  

  