﻿230 
  Crosby 
  — 
  Geology 
  of 
  Newport 
  Neck 
  and 
  Conanicut 
  Is. 
  

  

  Aet. 
  XXII. 
  — 
  Contribution 
  to 
  the 
  Geology 
  of 
  Newport 
  Neck 
  

   and 
  Conanicut 
  Island 
  ; 
  by 
  W. 
  6. 
  Ceosby. 
  

  

  The 
  granite 
  of 
  Newport 
  Neck 
  and 
  Conanicut 
  Island 
  was 
  

   regarded 
  by 
  C. 
  T. 
  Jackson* 
  as 
  intrusive, 
  and 
  as 
  having 
  altered 
  

   the 
  Carboniferous 
  shales 
  to 
  siliceous 
  and 
  epidotic 
  slates. 
  

   Edward 
  Hitchcockf 
  held 
  a 
  similar 
  view 
  ; 
  while 
  C. 
  H. 
  

   Hitchcock^ 
  has 
  described 
  the 
  granite 
  as 
  post-Carboniferous, 
  

   and 
  the 
  siliceous 
  slate 
  as 
  intermediate 
  in 
  age 
  between 
  the 
  

   Carboniferous 
  and 
  the 
  granite. 
  

  

  In 
  1876, 
  while 
  collecting 
  data 
  for 
  the 
  Centennial 
  Geological 
  

   Map 
  of 
  Massachusetts, 
  I 
  made 
  a 
  hurried 
  examination 
  of 
  the 
  

   Newport 
  area, 
  reaching 
  the 
  conclusion 
  that 
  the 
  granitic 
  rocks 
  

   are 
  more 
  recent 
  than 
  the 
  flinty 
  slates, 
  which 
  they 
  freely 
  inter- 
  

   sect, 
  and 
  older 
  than 
  the 
  grits, 
  shales, 
  and 
  conglomerates 
  of 
  the 
  

   Carboniferous 
  series; 
  and 
  provisionally 
  correlating 
  the 
  flinty 
  

   slates 
  with 
  the 
  Cambrian 
  beds 
  of 
  the 
  Boston 
  basin. 
  These 
  

   unpublished 
  views 
  concerning 
  the 
  relative 
  ages 
  and 
  relations 
  

   of 
  the 
  rocks 
  and 
  the 
  essential 
  distinctness 
  of 
  the 
  flinty 
  slates 
  

   and 
  the 
  Carboniferous 
  series 
  were 
  fully 
  confirmed 
  by 
  a 
  more 
  

   detailed 
  study 
  made 
  ten 
  years 
  later, 
  in 
  1886, 
  in 
  company 
  with 
  

   G. 
  H. 
  Barton. 
  

  

  Meanwhile, 
  in 
  1883 
  and 
  1884, 
  T. 
  N. 
  Dale§ 
  had 
  made 
  his 
  

   important 
  contribution 
  to 
  the 
  geology 
  of 
  this 
  region, 
  in 
  which 
  

   he 
  clearly 
  recognized 
  the 
  three 
  distinct 
  series 
  of 
  rocks, 
  but 
  

   failed 
  to 
  regard 
  the 
  granite 
  (" 
  protogine 
  ") 
  as 
  intrusive 
  in 
  the 
  

   flinty 
  slate, 
  making 
  it 
  the 
  oldest 
  of 
  the 
  three 
  series. 
  Three 
  

   years 
  ago 
  (1893) 
  L. 
  V. 
  Pirsson| 
  studied 
  the 
  rocks 
  of 
  Conanicut 
  

   Island, 
  apparently 
  paying 
  no 
  attention 
  to 
  the 
  similar 
  forma- 
  

   tions 
  on 
  Newport 
  Neck, 
  and 
  reached 
  the 
  conclusions 
  that 
  the 
  

   granite 
  is 
  the 
  youngest 
  rock 
  formation 
  on 
  the 
  island, 
  that 
  it 
  is 
  

   intrusive 
  in 
  the 
  Carboniferous 
  strata 
  (shales) 
  and 
  that 
  the 
  flinty 
  

   slate 
  is 
  merely 
  a 
  contact 
  zone 
  between 
  the 
  granite 
  and 
  shales, 
  a 
  

   portion 
  of 
  the 
  shales 
  which 
  have 
  suffered 
  contact 
  metamorph- 
  

   ism 
  through 
  the 
  influence 
  of 
  the 
  granite 
  and 
  show 
  a 
  gradation 
  

   from 
  the 
  most 
  typical 
  hornstone 
  into 
  unaltered 
  fissile 
  shales. 
  

   Still 
  more 
  recently 
  (1894) 
  Collie^ 
  has 
  published 
  a 
  somewhat 
  

   elaborate 
  account 
  of 
  the 
  geology 
  of 
  Conanicut 
  Island, 
  in 
  which 
  

   he 
  agrees 
  with 
  Dale 
  in 
  regarding 
  the 
  flinty 
  slate 
  as 
  distinct 
  

   from 
  the 
  Carboniferous 
  series 
  and 
  older 
  than 
  the 
  granite. 
  

  

  Since 
  the 
  publication 
  of 
  Pirsson's 
  paper, 
  I 
  have 
  desired 
  to 
  

   re-examine 
  the 
  relations 
  of 
  the 
  granite 
  to 
  the 
  sedimentary 
  

  

  *Geol. 
  Survey 
  E. 
  I, 
  1840, 
  40, 
  89-92. 
  

  

  f 
  Geology 
  of 
  Massachusetts, 
  1841, 
  537, 
  540, 
  550, 
  552. 
  

  

  \ 
  Proc. 
  Amer. 
  Assoc. 
  Adv. 
  Sci., 
  1860, 
  119, 
  121-126, 
  129-133, 
  136-137. 
  

  

  § 
  This 
  Journal, 
  III, 
  xxvii, 
  217-228, 
  282-291. 
  || 
  Ibid, 
  III, 
  xlvi, 
  363-378. 
  

  

  1 
  Trans. 
  Wis. 
  Acad. 
  Sci., 
  x, 
  199-230. 
  

  

  