﻿290 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  containing 
  no 
  thick 
  bed 
  of 
  limestone. 
  To 
  make 
  a 
  section 
  at 
  any 
  par- 
  

   ticular 
  locality 
  would 
  be 
  of 
  little 
  value 
  unless 
  half 
  a 
  dozen 
  others 
  were 
  

   made 
  for 
  comparison. 
  

  

  The 
  only 
  persistent 
  feature 
  is 
  a 
  thin 
  stratum 
  of 
  buff 
  sandy 
  limestone, 
  

   in 
  the 
  upper 
  portion, 
  never 
  over 
  10 
  inches 
  in 
  thickness. 
  It 
  extends 
  from 
  

   Smoky 
  Hill 
  Valley 
  northeasterly 
  into 
  Nebraska. 
  It 
  contains 
  Inocera- 
  

   mus 
  problematicus, 
  Gryplieu^ 
  Belemnite, 
  and 
  an 
  Am/Monite, 
  all 
  poorly 
  fjre- 
  

   served, 
  and, 
  excepting 
  the 
  first, 
  too 
  indistinct 
  for 
  specific 
  identification. 
  

   It 
  is 
  much 
  used 
  as 
  a 
  building-stone 
  on 
  the 
  whole 
  line 
  named. 
  It 
  is 
  soft, 
  

   fine-grained, 
  and 
  easily 
  wrought, 
  and 
  its 
  color 
  is 
  pleasing 
  to 
  the 
  eye. 
  

  

  The 
  line 
  of 
  division 
  between 
  the 
  Dakota 
  and 
  Fort 
  Hays 
  is 
  very 
  ob- 
  

   scure, 
  and 
  the 
  shales 
  appear 
  to 
  shade 
  into 
  each 
  other, 
  in 
  such 
  a 
  manner 
  

   as 
  to 
  indicate 
  that 
  no 
  interval 
  of 
  time 
  intervened 
  between 
  the 
  last 
  

   deposition 
  of 
  the 
  one 
  or 
  the 
  first 
  of 
  the 
  other. 
  Near 
  the 
  apparent 
  

   division 
  there 
  are 
  scarcely 
  any 
  fossils, 
  and 
  those 
  in 
  poor 
  preservation, 
  

   which 
  renders 
  the 
  tracing 
  of 
  the 
  dividing 
  line 
  more 
  diificuit. 
  In 
  the 
  

   Arkansas 
  Valley, 
  both 
  bend 
  toward 
  Colorado. 
  During 
  two 
  weeks 
  spent 
  

   in 
  this 
  valley 
  west 
  of 
  Fort 
  Dodge, 
  I 
  collected 
  only 
  a 
  few 
  obscure 
  frag- 
  

   ments 
  of 
  an 
  Inoceramus 
  and 
  fish-teeth, 
  and 
  no 
  leaves. 
  Yet 
  in 
  1876, 
  

   Prof. 
  M. 
  V. 
  B. 
  Knox 
  collected 
  a 
  few 
  leaves 
  (Phylites, 
  (fee), 
  apparently 
  

   of 
  the 
  Dakota, 
  near 
  Fort 
  Lyon, 
  Colo., 
  very 
  near 
  the 
  geological 
  horizon 
  

   of 
  the 
  sandstone, 
  which 
  extends 
  from 
  Fort 
  Dodge 
  to 
  the 
  Colorado 
  line. 
  

   All 
  our 
  Cretaceous 
  groups 
  lose 
  most 
  of 
  their 
  characteristic 
  fossils 
  as 
  

   they 
  approach 
  the 
  western 
  line 
  of 
  the 
  State. 
  Near 
  the 
  Nebraska 
  line, 
  

   in 
  Eepublic 
  County, 
  the 
  transition 
  from 
  one 
  group 
  to 
  the 
  other 
  is 
  more 
  

   rapid 
  and 
  clearly 
  defined. 
  

  

  Under 
  the 
  heavy 
  bed 
  of 
  limestone, 
  forming 
  the 
  highest 
  portion 
  of 
  

   the 
  Fort 
  Hays 
  group, 
  is 
  seen 
  a 
  friable, 
  bluish-black, 
  or 
  slate-colored 
  

   shale. 
  It 
  abounds 
  in 
  concretions, 
  or 
  septaria, 
  of 
  all 
  sizes 
  from 
  1 
  inch 
  

   to 
  6 
  feet 
  in 
  diameter. 
  The 
  body 
  of 
  the 
  concretions 
  is 
  of 
  hard 
  clay-marl 
  

   with 
  cracks 
  lined 
  with 
  beautiful 
  crystals 
  of 
  calc-spar. 
  These 
  cracks 
  

   frequently 
  extend 
  to 
  the 
  outside, 
  and 
  are 
  then 
  filled 
  with 
  a 
  light 
  lime, 
  

   which 
  gives 
  them 
  fanciful 
  markings, 
  inducing 
  several 
  persons 
  to 
  send 
  

   small 
  ones 
  to 
  me 
  as 
  *' 
  fossil 
  turtles". 
  This 
  stratum 
  is 
  well 
  exposed 
  near 
  

   the 
  railroad, 
  a 
  few 
  miles 
  west 
  of 
  Fort 
  Hays, 
  and 
  in 
  most 
  places 
  where 
  

   the 
  massive 
  limestone 
  lies 
  on 
  the 
  high 
  bluffs. 
  It 
  is 
  about 
  60 
  feet 
  in 
  

   thickness, 
  and 
  frequently 
  contains 
  fine 
  clusters 
  of 
  compound 
  crystals 
  of 
  

   selenite. 
  It 
  affords 
  a 
  few 
  fish 
  and 
  saurian 
  remains. 
  It 
  is 
  more 
  noted, 
  

   especially 
  in 
  the 
  Saline 
  and 
  Solomon 
  Valleys, 
  for 
  the 
  number 
  and 
  va- 
  

   riety 
  of 
  its 
  Ammonites, 
  embracing 
  several 
  species, 
  from 
  1 
  to 
  30 
  inches 
  

   in 
  diameter. 
  The 
  most 
  common 
  is 
  Prionocyclus 
  woolgari. 
  The 
  larger 
  

   specimens 
  are 
  almost 
  invariably 
  in 
  fragments, 
  although 
  a 
  portion 
  of 
  the 
  

   original 
  shell-substance 
  of 
  a 
  bright 
  pearly 
  luster 
  is 
  still 
  to 
  be 
  seen. 
  

   Forms 
  allied 
  to 
  the 
  Ammonites 
  are 
  also 
  found, 
  as 
  Scaphites, 
  Morto- 
  

   nicems, 
  &c., 
  and 
  also 
  several 
  Inocerami, 
  one 
  near 
  I. 
  nehrascencis 
  of 
  Owen. 
  

  

  Some 
  of 
  the 
  lower 
  strata 
  give 
  thin 
  impure 
  beds 
  of 
  lignite, 
  but 
  no 
  

   I)lants 
  could 
  be 
  identified 
  from 
  them. 
  

  

  The 
  total 
  thickness 
  of 
  the 
  Fort 
  Hays 
  group 
  is 
  260 
  feet. 
  

  

  2.— 
  Dakota. 
  

  

  The 
  Dakota 
  group 
  includes 
  all 
  the 
  Cretaceous 
  east 
  of 
  the 
  Niobrara. 
  

   As 
  no 
  fossils 
  of 
  the 
  Triassic 
  or 
  Jurassic 
  have 
  yet 
  been 
  discovered, 
  after 
  

   ten 
  years' 
  search, 
  we 
  conclude 
  that 
  the 
  Dakota 
  rests 
  directly 
  on 
  the 
  

   Permian. 
  While 
  the 
  dividiug-line 
  has 
  not 
  usually 
  been 
  very 
  well 
  

   defined, 
  yet 
  in 
  a 
  few 
  instances 
  the 
  fossils 
  of 
  the 
  Permo-Carbouiferous 
  

  

  