﻿E. 
  H. 
  Perkins 
  — 
  Dighton 
  Conglomerate. 
  63 
  

  

  Topographically, 
  the 
  basin 
  may 
  be 
  divided 
  into 
  two 
  

   distinct 
  areas, 
  a 
  northern 
  and 
  a 
  southern. 
  The 
  southern 
  

   section 
  consists 
  of 
  Narragansett 
  Bay, 
  its 
  islands 
  and 
  a 
  

   narrow 
  belt 
  on 
  either 
  shore. 
  The 
  bay 
  is 
  a 
  drowned 
  val- 
  

   ley, 
  while 
  the 
  islands 
  are 
  hills 
  rising 
  from 
  the 
  old 
  valley 
  

   floor. 
  The 
  hills 
  on 
  Aquidneck 
  Island 
  rise 
  to 
  260 
  feet 
  

   above 
  sea-level. 
  MacSparran 
  and 
  Hammond 
  hills 
  on 
  the 
  

   west 
  shore 
  are 
  nearly 
  the 
  same 
  height. 
  The 
  topography 
  

   is 
  in 
  a 
  state 
  of 
  early 
  maturity. 
  Some 
  of 
  the 
  hilltops 
  have 
  

   fairly 
  large 
  areas 
  of 
  level 
  land, 
  especially 
  in 
  the 
  north- 
  

   south 
  direction. 
  The 
  bay 
  section 
  of 
  the 
  basin 
  tends 
  in 
  

   a 
  north-south 
  direction. 
  The 
  rocks 
  are 
  highly 
  meta- 
  

   morphosed. 
  

  

  The 
  northern, 
  or 
  inland 
  section, 
  on 
  the 
  other 
  hand, 
  

   tends 
  in 
  a 
  northeast-southwest 
  direction, 
  while 
  the 
  rocks, 
  

   especially 
  toward 
  the 
  east, 
  are 
  much 
  less 
  metamorphosed 
  

   than 
  further 
  south. 
  The 
  country 
  is 
  rolling 
  in 
  character, 
  

   similar 
  to 
  the 
  drowned 
  section 
  further 
  south. 
  The 
  

   highest 
  elevation 
  is 
  Great 
  Meadow 
  Hill 
  which 
  is 
  263 
  feet 
  

   above 
  sea-level. 
  This 
  hill, 
  like 
  the 
  higher 
  portions 
  of 
  

   Aquidneck 
  island, 
  is 
  a 
  syncline 
  and 
  owes 
  its 
  elevation 
  to 
  

   the 
  resistant 
  Dighton 
  Conglomerate. 
  The 
  surrounding 
  

   country 
  underlaid 
  by 
  the 
  weaker 
  Coal 
  Measures 
  is 
  lower. 
  

  

  At 
  its 
  northwestern 
  corner 
  the 
  basin 
  is 
  connected 
  with 
  

   the 
  smaller 
  Norfolk 
  Basin. 
  At 
  all 
  other 
  points 
  it 
  is 
  sur- 
  

   rounded 
  by 
  intrusive 
  granites 
  and 
  highly 
  metamorphosed 
  

   sediments. 
  

  

  The 
  Carboniferous 
  sediments 
  which 
  make 
  up 
  the 
  basin 
  

   consist 
  of 
  shales, 
  sandstones, 
  arkoses 
  and 
  conglomerates. 
  

   The 
  series 
  is 
  as 
  follows 
  : 
  

  

  Table 
  I. 
  Formations 
  of 
  the 
  Narragansett 
  Basin. 
  

  

  Dighton 
  Conglomerate 
  1,000-1,500 
  ft. 
  

  

  Rhode 
  Island 
  formation 
  j 
  ? 
  q 
  ^™les 
  10,000 
  

  

  j 
  ggg* 
  ™ 
  tones 
  1>000 
  „ 
  

  

  Pondville 
  conglomerate 
  and 
  arkose 
  100 
  ' 
  ' 
  

  

  (Modified 
  from 
  Woodworth.) 
  3 
  

  

  In 
  this 
  paper 
  the 
  lower 
  formations 
  will 
  be 
  considered 
  

   only 
  as 
  they 
  throw 
  light 
  on 
  the 
  origin 
  of 
  the 
  Dighton 
  

   conglomerate. 
  

  

  3 
  Shaler, 
  N. 
  S., 
  Woodworth, 
  J. 
  B. 
  and 
  Foerste, 
  A. 
  F., 
  Geology 
  of 
  the 
  

   Narragansett 
  Basin, 
  U. 
  S. 
  Geol. 
  Survey, 
  Mon. 
  33, 
  134, 
  1899. 
  

  

  