﻿GEOLOGICAL 
  AGE 
  OF 
  THE 
  TACONIC 
  SYSTEM. 
  397 
  

  

  41. 
  Geological 
  Age 
  of 
  the 
  Taconic 
  System. 
  

   By 
  Prof. 
  James 
  D. 
  Dana, 
  F.M.G.S. 
  (Eead 
  April 
  5, 
  1882.) 
  

  

  [Plate 
  XVII.] 
  

  

  A 
  PAJiAGEAPH 
  in 
  the 
  ' 
  Proceedings 
  of 
  the 
  Geological 
  Society 
  ' 
  for 
  the 
  

   16th 
  of 
  November 
  last, 
  making 
  part 
  of 
  an 
  abstract 
  of 
  an 
  address 
  by 
  

   Dr. 
  T. 
  Sterry 
  Hunt 
  sustaining 
  the 
  pre-Cambrian 
  age 
  of 
  the 
  Taconic 
  

   schists, 
  throws 
  more 
  doubt 
  than 
  is 
  right 
  on 
  the 
  stratigraphical 
  ob- 
  

   servations 
  that 
  have 
  been 
  made 
  in 
  the 
  region 
  by 
  different 
  geologists. 
  

   It 
  does 
  not 
  present, 
  as 
  a 
  reason 
  for 
  doubt, 
  any 
  facts 
  from 
  the 
  

   author's 
  personal 
  investigation 
  convicting 
  these 
  geologists 
  of 
  errors 
  

   in 
  their 
  statements 
  or 
  conclusions, 
  but 
  simply 
  mentions 
  what 
  the 
  

   author 
  regards 
  as 
  a 
  possible 
  source 
  of 
  error 
  in 
  any 
  study 
  of 
  folded 
  

   metamorphic 
  strata, 
  and 
  urges 
  this 
  as 
  a 
  probable 
  source 
  in 
  the 
  pre- 
  

   sent 
  case. 
  

  

  The 
  paragraph 
  says 
  : 
  — 
  " 
  The 
  speaker 
  insisted 
  upon 
  the 
  fact 
  that 
  

   where 
  newer 
  strata 
  are 
  in 
  unconformable 
  contact 
  with 
  older 
  ones, 
  

   the 
  effect 
  of 
  lateral 
  movements 
  of 
  compression, 
  involving 
  the 
  two 
  

   series, 
  is 
  generally 
  to 
  cause 
  the 
  newer 
  and 
  more 
  yielding 
  strata 
  to 
  

   dip 
  towards, 
  and 
  even 
  beneath 
  the 
  edges 
  of 
  the 
  older 
  rock, 
  a 
  result 
  

   due 
  to 
  folds, 
  often 
  with 
  inversion, 
  sometimes 
  passing 
  into 
  faults. 
  

   This 
  phenomenon 
  throws 
  much 
  light 
  on 
  the 
  supposed 
  recency 
  of 
  

   many 
  crystalline 
  schists.*' 
  

  

  The 
  supposed 
  recency 
  of 
  the 
  Taconic 
  schists, 
  and 
  the 
  observations 
  

   which 
  have 
  led 
  to 
  the 
  inference 
  that 
  these 
  schists 
  overlie 
  certain 
  

   Lower 
  Silurian 
  strata, 
  are 
  among 
  the 
  points 
  to 
  which 
  the 
  paragraph 
  

   is 
  meant 
  especially 
  to 
  apply. 
  It 
  implies 
  that 
  in 
  any 
  overlying, 
  ap- 
  

   parent 
  or 
  actual, 
  it 
  is 
  an 
  overlying 
  of 
  newer 
  strata, 
  unconformably 
  . 
  

  

  The 
  Taconic 
  system, 
  first 
  propounded 
  by 
  Prof. 
  E. 
  Emmons 
  about 
  

   forty 
  years 
  since, 
  in 
  his 
  New- 
  York 
  Geological 
  Report, 
  published 
  in 
  

   1842*, 
  has 
  found 
  a 
  place, 
  right 
  or 
  wrong, 
  in 
  European 
  as 
  well 
  as 
  

   American 
  geological 
  science. 
  Whether 
  right 
  or 
  wrong 
  is 
  therefore 
  

   a 
  question 
  of 
  the 
  highest 
  importance. 
  I 
  have 
  hence 
  thought 
  that 
  a 
  

   brief 
  review 
  of 
  the 
  facts 
  bearing 
  on 
  the 
  two 
  points 
  of 
  conform 
  ability 
  

   to 
  the 
  associated 
  rocks 
  and 
  geological 
  age 
  by 
  one 
  of 
  the 
  workers 
  in 
  

   the 
  field 
  would 
  be 
  acceptable 
  to 
  the 
  Geological 
  Society. 
  

  

  The 
  true 
  original 
  Taconic 
  schists 
  are 
  those 
  of 
  the 
  Taconic 
  moun- 
  

   tain-range, 
  at 
  the 
  base 
  of 
  one 
  portion 
  of 
  which 
  Prof. 
  Emmons 
  for 
  

   many 
  years 
  lived 
  and 
  laboured. 
  The 
  range 
  stands 
  along 
  the 
  

   boundary 
  region 
  between 
  the 
  States 
  of 
  Massachusetts 
  and 
  New 
  

   York, 
  extends 
  thence 
  northward 
  through 
  Western 
  Vermont 
  to 
  its 
  

   centre, 
  and 
  southward 
  across 
  north-western 
  Connecticut 
  into 
  and 
  

   through 
  Dutchess 
  County, 
  New 
  York. 
  The 
  general 
  course 
  of 
  the 
  

  

  * 
  Geology 
  of 
  New 
  York: 
  part 
  ii., 
  comprising 
  the 
  survey 
  of 
  the 
  Second 
  Geo- 
  

   logical 
  District 
  ; 
  by 
  Ebenezer 
  Emmons, 
  M.D., 
  Prof. 
  Nat. 
  Hist, 
  in 
  Williams 
  

   College, 
  "Williamstown, 
  Berkshire 
  Co., 
  Mass. 
  438 
  pp. 
  4to, 
  with 
  17 
  plates, 
  

   Albany, 
  N. 
  York, 
  1842, 
  

  

  