﻿Formations 
  of 
  Southeastern 
  Idaho. 
  405 
  

  

  In 
  addition 
  to 
  the 
  conglomerates 
  there 
  are 
  beds 
  of 
  

   white 
  marls, 
  calcareous 
  clays, 
  sandstones, 
  and 
  grits. 
  

   These 
  furnish 
  a 
  white 
  soil 
  and 
  underlie 
  considerable 
  

   areas, 
  particularly 
  north 
  of 
  Ovid 
  and 
  a 
  mile 
  or 
  more 
  

   north 
  of 
  Georgetown. 
  At 
  the 
  last 
  named 
  locality 
  some 
  

   of 
  the 
  white 
  calcareous 
  beds 
  contain 
  much 
  rhyolitic 
  mate- 
  

   rial, 
  in 
  the 
  form 
  of 
  glassy 
  fragments 
  of 
  the 
  walls 
  of 
  bub- 
  

   bles, 
  and 
  resemble 
  parts 
  of 
  the 
  Fowkes 
  formation 
  of 
  

   Veatch 
  in 
  the 
  Eocene 
  of 
  southwestern 
  Wyoming. 
  Beds 
  

   of 
  this 
  type, 
  however, 
  are 
  common 
  in 
  sediments 
  of 
  sup- 
  

   posed 
  Pliocene 
  age 
  in 
  the 
  Fort 
  Hall 
  Indian 
  Reservation. 
  

  

  The 
  thickness 
  of 
  the 
  formation 
  varies 
  from 
  a 
  few 
  

   inches 
  at 
  places 
  bordering 
  exposures 
  of 
  older 
  terranes 
  to 
  

   more 
  than 
  1,000 
  feet 
  where 
  old 
  valleys 
  filled 
  with 
  these 
  

   beds 
  have 
  been 
  re-excavated, 
  as 
  in 
  Georgetown 
  Canyon. 
  

   Great 
  erosion 
  has 
  occurred 
  since 
  these 
  sediments 
  were 
  

   deposited, 
  so 
  that 
  without 
  doubt 
  the 
  maximum 
  thickness 
  

   was 
  formerly 
  much 
  greater. 
  

  

  The 
  formation 
  is 
  in 
  many 
  places 
  nearly 
  horizontal, 
  but 
  

   at 
  other 
  places 
  it 
  is 
  inclined 
  at 
  angles 
  varying 
  from 
  a 
  few 
  

   degrees 
  to 
  nearly 
  vertical. 
  

  

  Some 
  fossils 
  have 
  been 
  collected 
  from 
  the 
  Salt 
  Lake 
  

   formation 
  but 
  these 
  are 
  chiefly 
  poorly 
  preserved 
  fresh- 
  

   water 
  mollusks, 
  which 
  are 
  not 
  of 
  determinative 
  value. 
  

   From 
  clayey 
  layers 
  among 
  conglomerate 
  bands 
  on 
  the 
  

   south 
  side 
  of 
  Montpelier 
  Creek 
  the 
  following 
  forms, 
  col- 
  

   lected 
  by 
  C. 
  L. 
  Breger, 
  were 
  identified 
  by 
  W. 
  H. 
  Dall 
  : 
  

  

  Pisidium 
  sp. 
  — 
  common. 
  

  

  Valvata 
  sp. 
  — 
  common. 
  

  

  Planorbis 
  (round 
  whorls, 
  low 
  spires) 
  rare 
  

  

  Lymnaea 
  sp. 
  — 
  rare. 
  

  

  Ostracods 
  — 
  abundant. 
  

  

  In 
  collections 
  from 
  T.10S., 
  R..42E., 
  a 
  short 
  distance 
  

   west 
  of 
  the 
  southern 
  part 
  of 
  the 
  Slug 
  Creek 
  quadrangle, 
  

   W. 
  H. 
  Dall 
  has 
  identified 
  imperfect 
  impressions 
  of 
  Pla- 
  

   norbis 
  and 
  Sphaerium 
  and 
  from 
  the 
  west 
  side 
  of 
  Bear 
  

   River 
  Valley 
  in 
  the 
  same 
  quadrangle 
  a 
  minute 
  Planorbis, 
  

   perhaps 
  undescribed. 
  

  

  A 
  collection 
  from 
  the 
  forks 
  of 
  Miller 
  Creek 
  in 
  the 
  

   NW.14 
  sec. 
  34, 
  T.5S., 
  R.46E., 
  in 
  the 
  northeastern 
  part 
  of 
  

   the 
  Freedom 
  quadrangle, 
  yielded 
  the 
  following 
  fossils 
  

   identified 
  by 
  Dall 
  and 
  thought 
  by 
  him 
  to 
  indicate 
  Eocene 
  

   age: 
  

  

  