﻿Richardson 
  — 
  Paleozoic 
  Section 
  in 
  Northern 
  Utah. 
  411 
  

  

  Devonian. 
  

   Jefferson 
  dolomite. 
  

  

  The 
  Jefferson 
  limestone 
  of 
  Lower 
  and 
  Middle 
  Devonian 
  age, 
  

   which 
  has 
  a 
  widespread 
  distribution 
  in 
  the 
  northern 
  Rocky 
  

   Mountain 
  region, 
  is 
  well 
  developed 
  in 
  the 
  Randolph 
  quadrangle, 
  

   where, 
  however, 
  the 
  name 
  dolomite 
  is 
  applied 
  instead 
  of 
  lime- 
  

   stone 
  because 
  of 
  the 
  magnesian 
  content. 
  A 
  sample 
  from 
  Lake- 
  

   town 
  Canyon 
  showed 
  the 
  presence 
  of 
  19'16 
  per 
  cent 
  MgO. 
  In 
  

   the 
  area 
  here 
  considered 
  the 
  Jefferson 
  consists 
  chiefly 
  of 
  massive 
  

   fine-grained 
  dark-colored 
  dolomite, 
  weathering 
  a 
  characteristic 
  

   brownish 
  tint, 
  but 
  in 
  places, 
  as 
  in 
  Laketown 
  canyon, 
  the 
  lower 
  

   strata 
  are 
  thiu-bedded. 
  The 
  Jefferson 
  is 
  about 
  1200 
  feet 
  thick. 
  

   and 
  overlies 
  the 
  Laketown 
  dolomite 
  apparently 
  conformably. 
  

   Fossils 
  are 
  not 
  abundant 
  although 
  two 
  collections 
  were 
  

   obtained 
  in 
  Laketown 
  Canyon, 
  one 
  from 
  near 
  the 
  top 
  of 
  the 
  

   dolomite 
  and 
  the 
  other 
  from 
  near 
  its 
  base. 
  Both 
  lots 
  were 
  

   identified 
  by 
  E. 
  M. 
  Kindle. 
  

  

  Fossils 
  from 
  Jefferson 
  dolomite, 
  Randolph 
  quadrangle. 
  

  

  From 
  East 
  Fork 
  of 
  Laketown 
  Canyon, 
  SEJ 
  sec. 
  17, 
  T. 
  12 
  

   !N\, 
  R. 
  6 
  E., 
  about 
  150 
  feet 
  above 
  the 
  base 
  of 
  the 
  formation 
  : 
  

  

  Productella 
  sp. 
  Aviculopeeten? 
  sp. 
  

  

  Spirifer 
  englemani 
  Fish 
  bone 
  fragment. 
  

  

  Nuculites 
  sp. 
  

  

  From 
  East 
  Fork 
  of 
  Laketown 
  Canyon, 
  W£ 
  sec. 
  17, 
  T. 
  12 
  

   N., 
  R. 
  6 
  E., 
  from 
  several 
  beds 
  between 
  200 
  and 
  500 
  feet 
  below 
  

   the 
  top 
  of 
  the 
  formation. 
  

  

  Aulopora 
  sp. 
  Zaphrentis 
  sp. 
  

  

  Favosites 
  cf. 
  limitaris 
  

  

  Dr. 
  Kindle 
  reports 
  that 
  " 
  the 
  coral 
  listed 
  here 
  as 
  Favosites 
  

   cf. 
  limitaris 
  is 
  one 
  of 
  the 
  characteristic 
  and 
  widely 
  distributed 
  

   fossils 
  of 
  the 
  Jefferson 
  limestone 
  of 
  the 
  northern 
  Rocky 
  

   Mountain 
  region. 
  One 
  of 
  the 
  species 
  of 
  the 
  preceding 
  faunule, 
  

   Spirifer 
  e?igle?nann/\ 
  is 
  also 
  a 
  characteristic 
  fossil 
  of 
  this 
  forma- 
  

   tion." 
  

  

  Threeforks 
  limestone. 
  

  

  At 
  the 
  type 
  locality, 
  Threeforks, 
  Montana, 
  the 
  Threeforks 
  

   limestone, 
  there 
  the 
  Threeforks 
  shale, 
  lies 
  conformably 
  

   between 
  the 
  Madison 
  and 
  Jefferson 
  limestones. 
  But 
  although 
  

   the 
  Threeforks 
  has 
  not 
  been 
  recognized 
  over 
  so 
  wide 
  an 
  area 
  

   as 
  have 
  the 
  immediately 
  overlying 
  and 
  underlying 
  formations, 
  

   in 
  the 
  Randolph 
  quadrangle 
  all 
  three 
  formations 
  are 
  present, 
  

   the 
  Threeforks 
  being 
  definitely 
  recognized 
  by 
  fossil 
  evidence. 
  

  

  The 
  Threeforks 
  limestone 
  is 
  a 
  soft 
  formation 
  lying 
  between 
  

   harder 
  ones 
  and 
  in 
  the 
  area 
  here 
  considered 
  usually 
  occupies 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  XXXVI, 
  No. 
  214. 
  — 
  October, 
  1913. 
  

  

  27 
  

  

  