﻿E. 
  H. 
  Perkins 
  — 
  Dighton 
  Conglomerate. 
  67 
  

  

  the 
  sedimentary 
  record 
  a 
  stratum 
  of 
  marine 
  conglom- 
  

   erate 
  exceeding 
  15 
  miles 
  in 
  breadth 
  and 
  100 
  feet 
  in 
  thick- 
  

   ness 
  would 
  be 
  anomalous. 
  As 
  compared 
  with 
  marine 
  

   action, 
  vigorous 
  streams 
  may 
  carry 
  gravel 
  during 
  a 
  

   single 
  cycle 
  3-300 
  times 
  farther 
  and 
  distribute 
  it 
  much 
  

   more 
  widely. 
  ' 
  ' 
  

  

  Matrix. 
  

  

  The 
  chief 
  features 
  of 
  the 
  matrix 
  to 
  be 
  explained 
  are: 
  

   the 
  unsorted 
  condition 
  of 
  the 
  material, 
  the 
  great 
  varia- 
  

   tion 
  in 
  amount, 
  and 
  the 
  presence 
  of 
  decomposable 
  min- 
  

   erals. 
  

  

  Like 
  the 
  coarser 
  material, 
  the 
  matrix 
  is 
  made 
  up 
  of 
  

   large 
  and 
  small 
  grains 
  irregularly 
  distributed. 
  In 
  al- 
  

   most 
  every 
  specimen 
  the 
  grains 
  range 
  from 
  fine 
  grit 
  up 
  

   to 
  the 
  small 
  pebbles 
  of 
  the 
  conglomerate. 
  As 
  a 
  rule, 
  

   however, 
  the 
  coarser 
  material 
  predominates. 
  Although 
  

   a 
  careful 
  search 
  was 
  made, 
  nothing 
  as 
  fine 
  as 
  rock 
  flour 
  

   was 
  found, 
  in 
  the 
  matrix 
  of 
  the 
  Squantum 
  tillite. 
  The 
  

   condition 
  of 
  the 
  matrix 
  thus 
  indicates 
  a 
  degree 
  of 
  sort- 
  

   ing 
  above 
  what 
  we 
  would 
  find 
  in 
  a 
  glacial 
  till, 
  but 
  still 
  

   very 
  imperfect. 
  This 
  would 
  suggest 
  a 
  fluviatile 
  rather 
  

   than 
  a 
  marine 
  origin. 
  

  

  In 
  certain 
  outcrops, 
  especially 
  in 
  the 
  Newport 
  region, 
  

   the 
  matrix 
  is 
  almost 
  wanting, 
  the 
  cobbles 
  being 
  laid 
  in 
  

   contact 
  with 
  each 
  other. 
  This 
  condition 
  may 
  be 
  due 
  in 
  

   part 
  to 
  compression, 
  which 
  has 
  granulated 
  the 
  quartz 
  

   grains 
  and 
  caused 
  the 
  development 
  of 
  a 
  large 
  amount 
  of 
  

   sericite, 
  especially 
  over 
  the 
  surfaces 
  of 
  the 
  cobbles. 
  

   Further 
  north 
  in 
  the 
  other 
  synclinal 
  areas 
  the 
  amount 
  

   of 
  matrix 
  varies 
  greatly 
  in 
  the 
  same 
  outcrop. 
  This 
  

   change 
  may 
  be 
  either 
  gradual 
  or 
  sudden 
  and 
  shows 
  no 
  

   regularity 
  as 
  to 
  direction. 
  In 
  the 
  case 
  of 
  a 
  marine 
  con- 
  

   glomerate, 
  one 
  would 
  expect 
  a 
  gradual 
  increase 
  in 
  the 
  

   amount 
  of 
  matrix 
  away 
  from 
  the 
  old 
  shore-line. 
  No 
  such 
  

   gradual 
  change 
  is 
  found 
  in 
  the 
  Narragansett 
  Basin. 
  

  

  In 
  many 
  cases 
  either 
  particles 
  of 
  feldspar 
  or 
  the 
  

   kaolinized 
  remains 
  of 
  such 
  particles 
  were 
  found. 
  In 
  

   specimens 
  in 
  which 
  the 
  particles 
  were 
  too 
  fine 
  to 
  be 
  dis- 
  

   tinguished 
  by 
  the 
  eye, 
  the 
  clayey 
  smell 
  of 
  kaolin 
  could 
  

   be 
  detected. 
  In 
  a 
  few 
  cases 
  particles 
  of 
  biotite 
  were 
  

   found, 
  and 
  in 
  the 
  northern 
  syncline 
  where 
  there 
  has 
  been 
  

   slight 
  metamorphism 
  the 
  rocks 
  contained 
  scattered 
  frag- 
  

   ments 
  of 
  muscovite 
  which 
  did 
  not 
  appear 
  to 
  be 
  of 
  second- 
  

  

  