﻿E. 
  H. 
  Perkins 
  — 
  Dighton 
  Conglomerate. 
  61 
  

  

  Art. 
  IV. 
  — 
  The 
  Origin 
  of 
  the 
  Dighton 
  Conglomerate 
  of 
  

   the 
  Narragansett 
  Basin 
  of 
  Massachusetts, 
  and 
  Rhode 
  

   Island; 
  by 
  Edward 
  H. 
  Perkins. 
  1 
  

  

  Introduction. 
  

  

  The 
  Dighton 
  Conglomerate 
  forms 
  the 
  npper 
  portion 
  

   of 
  the 
  Carboniferous 
  series 
  of 
  the 
  Narragansett 
  Basin. 
  

   The 
  rocks 
  consist 
  of 
  coarse 
  qnartzite 
  and 
  granite 
  con- 
  

   glomerates 
  interstratified 
  with 
  sandstones, 
  shales, 
  and, 
  

   in 
  some 
  cases, 
  coaly 
  beds. 
  Since 
  the 
  time 
  of 
  deposition 
  

   this 
  formation, 
  along 
  with 
  the 
  lower 
  members 
  of 
  the 
  

   series, 
  has 
  undergone 
  severe 
  dynamic 
  metamorphism. 
  

   A 
  careful 
  study 
  of 
  this 
  metamorphism 
  has 
  been 
  made 
  by 
  

   Lahee. 
  2 
  As 
  the 
  result 
  of 
  this 
  action 
  the 
  rocks 
  have 
  been 
  

   so 
  deformed 
  that 
  the 
  determination 
  of 
  original 
  structures 
  

   and 
  the 
  shapes 
  of 
  the 
  pebbles 
  is 
  difficult. 
  This 
  is 
  espe- 
  

   cially 
  true 
  in 
  the 
  southern 
  part 
  of 
  the 
  basin. 
  Once 
  

   spread 
  over 
  an 
  area 
  at 
  least 
  40 
  miles 
  long 
  by 
  15 
  miles 
  

   wide, 
  the 
  conglomerate 
  is 
  exposed 
  today 
  in 
  a 
  series 
  of 
  

   synclines 
  surrounded 
  by 
  the 
  older 
  formations. 
  (Fig. 
  1.) 
  

  

  The 
  field 
  work 
  upon 
  which 
  this 
  paper 
  is 
  based 
  was 
  

   carried 
  on 
  during 
  parts 
  of 
  the 
  summers 
  of 
  1916, 
  1917 
  and 
  

   1918. 
  Eealizing 
  that 
  the 
  determination 
  of 
  the 
  origin 
  of 
  

   the 
  formation 
  must 
  be 
  a 
  comparative 
  study, 
  attention 
  

   was 
  also 
  given 
  to 
  other 
  conglomerates. 
  The 
  Eoxbury 
  

   conglomerate 
  and 
  the 
  Squantum 
  tillite 
  of 
  the 
  Boston 
  

   Basin, 
  the 
  Trias 
  sic 
  conglomerate 
  of 
  the 
  Connecticut 
  Val- 
  

   ley, 
  and 
  the 
  Lafayette 
  and 
  Columbian 
  formations 
  near 
  

   Washington, 
  D. 
  C, 
  were 
  examined 
  in 
  the 
  field. 
  Tills, 
  

   aqueoglacial 
  deposits 
  and 
  beach 
  gravels 
  were 
  also 
  

   studied. 
  

  

  The 
  writer 
  wishes 
  to 
  express 
  his 
  indebtedness 
  to 
  the 
  

   Geological 
  Faculty 
  of 
  Yale 
  University, 
  especially 
  to 
  the 
  

   late 
  Professor 
  Barrell. 
  It 
  was 
  the 
  latter 
  who 
  first 
  inter- 
  

   ested 
  him 
  in 
  problems 
  of 
  sedimentation. 
  Professor 
  

   Charles 
  Brown 
  of 
  Brown 
  University 
  also 
  aided 
  by 
  help- 
  

   ful 
  advice 
  in 
  regard 
  to 
  the 
  field 
  work. 
  

  

  1 
  The 
  present 
  paper 
  is 
  a 
  digest 
  of 
  a 
  dissertation 
  accepted 
  for 
  the 
  degree 
  

   of 
  Doctor 
  of 
  Philosophy 
  in 
  Geology 
  at 
  Yale 
  University, 
  June, 
  1919. 
  

  

  2 
  Lahee, 
  F. 
  H., 
  Eelations 
  of 
  the 
  Degree 
  of 
  Metamorphism 
  to 
  Geological 
  

   Structure 
  and 
  to 
  Acid 
  Igneous 
  Intrusion 
  in 
  the 
  Narragansett 
  Basin, 
  E. 
  I., 
  

   this 
  Journal 
  (4), 
  33, 
  249-262, 
  354-372, 
  447-469, 
  1912. 
  

  

  