﻿Formations 
  of 
  Southeastern 
  Idaho. 
  401 
  

  

  ular 
  sandstone 
  beds, 
  closely 
  resembling 
  (1) 
  lithologically 
  

   but 
  separated 
  from 
  (1) 
  and 
  (2) 
  by 
  an 
  unconformity. 
  . 
  

  

  Gr. 
  B. 
  Richardson, 
  4 
  and 
  later 
  P. 
  V. 
  Roundy, 
  with 
  the 
  

   writer, 
  have 
  examined 
  parts 
  of 
  the 
  field 
  described 
  by 
  

   Veatch. 
  They 
  have 
  come 
  to 
  the 
  view 
  that 
  the 
  Fowkes 
  

   formation 
  may 
  in 
  reality 
  be 
  a 
  lens 
  and 
  that 
  the 
  postulate 
  

   of 
  unconformity 
  between 
  the 
  Knight 
  and 
  Almy 
  forma- 
  

   tions, 
  which 
  closely 
  resemble 
  each 
  other 
  lithologically, 
  is 
  

   doubtful 
  or, 
  at 
  least, 
  not 
  compulsory. 
  More 
  extended 
  

   study 
  of 
  the 
  Tertiary 
  formations 
  of 
  the 
  general 
  region 
  of 
  

   southwestern 
  Wyoming 
  and 
  northern 
  Utah 
  will 
  be 
  nec- 
  

   essary 
  before 
  a 
  definite 
  opinion 
  on 
  the 
  matter 
  can 
  be 
  

   rendered. 
  

  

  In 
  southeastern 
  Idaho 
  the 
  Fowkes 
  formation 
  has 
  not 
  

   been 
  definitely 
  recognized 
  although 
  at 
  one 
  locality 
  rhyoli- 
  

   tic 
  debris 
  has 
  been 
  found 
  in 
  beds 
  at 
  present 
  assigned 
  to 
  

   the 
  Pliocene 
  (?). 
  It 
  is, 
  too, 
  impracticable 
  to 
  distinguish 
  

   the 
  Almy 
  and 
  Knight 
  formations. 
  The 
  Eocene 
  rocks 
  are 
  

   therefore 
  described 
  under 
  the 
  name 
  Wasatch 
  formation. 
  

  

  The 
  principal 
  areas 
  occupied 
  by 
  the 
  Wasatch 
  forma- 
  

   tion 
  are 
  in 
  the 
  Bear 
  Lake 
  Plateau, 
  southeast 
  of 
  which 
  the 
  

   formation 
  is 
  practically 
  continuous 
  with 
  the 
  Wasatch 
  

   beds 
  described 
  by 
  Veatch 
  in 
  southwestern 
  Wyoming, 
  and 
  

   west 
  of 
  Bear 
  Lake. 
  Northward 
  there 
  are 
  patches 
  of 
  

   greater 
  or 
  less 
  size 
  in 
  parts 
  of 
  the 
  Montpelier 
  and 
  Slug 
  

   Creek 
  quadrangles. 
  The 
  irregularities 
  of 
  shape, 
  size, 
  

   and 
  distribution 
  of 
  these 
  patches 
  of 
  the 
  Wasatch 
  forma- 
  

   tion 
  all 
  indicate 
  that 
  the 
  sediments 
  now 
  found 
  are 
  but 
  

   erosional 
  remnants 
  of 
  a 
  formerly 
  much 
  more 
  extensive 
  

   deposit. 
  

  

  The 
  Wasatch 
  formation 
  of 
  southeastern 
  Idaho, 
  so 
  far 
  

   as 
  examined, 
  consists 
  mainly 
  of 
  coarse 
  red 
  conglomerate 
  

   with 
  pebbles 
  or 
  bowlders 
  ranging 
  from 
  a 
  fraction 
  of 
  an 
  

   inch 
  to 
  three 
  feet 
  or 
  more 
  in 
  diameter, 
  largely 
  subangu- 
  

   lar, 
  though 
  some 
  are 
  well 
  worn 
  and 
  rounded, 
  and 
  con- 
  

   sisting 
  chiefly 
  of 
  Paleozoic 
  quartzites 
  and 
  limestones, 
  

   including 
  many 
  of 
  Cambrian 
  and 
  Ordovician 
  age. 
  In 
  

   the 
  southeastern 
  part 
  of 
  T.10S., 
  R.43E. 
  (southern 
  part 
  

   of 
  the 
  Slug 
  Creek 
  quadrangle) 
  bowlders 
  of 
  basalt 
  were 
  

   noted 
  with 
  the 
  conglomerate. 
  The 
  grouping 
  of 
  the 
  

   bowlders 
  is 
  such 
  as 
  to 
  suggest 
  a 
  small 
  extrusion. 
  Since 
  

   no 
  actual 
  ledge 
  of 
  basalt 
  was 
  observed, 
  these 
  bowlders 
  

   may 
  have 
  formed 
  part 
  of 
  the 
  conglomerate, 
  though 
  their 
  

  

  4 
  Personal 
  communication. 
  

  

  