224  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
the  Yampa  Ulateau  was  uplifted  bodily,  developing  a  double  anticlinal  at  its  western 
extremity,  which  merges  into  a  single  fold  at  the  east  end,  while  the  sharp,  rectangu- 
lar folds  on  cither  flank  were  accompanied  by  a  certain  amount  of  dislocation  *  *  * 
T<  >  the  north  of  the  Archean  body  of  Red  Creek  was  also  some  disturbance  *  *  * 
in  the  vicinity  of  Bitter  Creek,  and  on  the  western  edge  of  the  basin  a  series  of  nar- 
row ,  wave-like  ridges  were  formed,  having  a  direction  resultant  of  that  of  the  shores 
of  the  Uinta  and  Wasatch  mountains,  whose  influences  in  the  folding  are  seen  in  the 
two  independent  directions  of  strike  found  in  these  ridges. « 
The  above  quotations,  from  the  general  descriptions  of  features 
observed  by  the  geologists  of  the  fortieth  parallel,  present  the  broad 
facts  of  structure  and  sedimentation.  They  show  also  that  one  of  the 
great  problems,  which,  in  the  absence  of  conclusive  evidence,  was  left 
an  open  question,  was  the  age  of  the  rocks  constituting  the  great  cen- 
tral area  of  the  range.  It  appears  that  the  discovery  of  an  uncon- 
formity by  Powell  in  the  eastern  Uintas  was  considered  by  Emmons 
as  explanatory  of  the  otherwise  inexplicable  thickness  of  siliceous  beds, 
and  that  accordingly  these  rocks  of  the  interior  were  tentatively  sup- 
posed to  be  Cambrian. 
In  the  middle  eighties  White  encountered  the  same  problem.  He 
states: 
Much  difference  of  opinion  has  prevailed  as  to  the  true  geological  age  of  the  Uinta 
sandstone.  King,  who  gave  it  the  name  of  Weber  quartzite,  states  that  it  is  of  Car- 
boniferous age,  in  which  view  Hague  and  Emmons  concur.  Powell  referred  it  pro- 
visionally to  the  Devonian;  Marsh  was  disposed  to  regard  it  as  belonging  to  the  Silu- 
rian, at  least  in  part;  and  Hay  den  was  of  the  opinion  that  it  ought  to  be  referred  to 
the  Lower  Silurian. 
Whatever  may  be  the  geological  age  of  the  Uinta  sandstone,  it  is  certain  that  the 
undoubted  Carboniferous  rocks  of  this  district  rest  directly  upon  it,  and,  according 
to  Powell,  there  is  in  many  places  distinct  unconformity  between  them.  It  is  also 
true  that  within  this  district  no  other  rocks  than  the  Archean  have  been  found 
beneath  the  Uinta  sandstone. b 
Although  in  the  course  of  such  rapid  traversing  as  is  required  on 
reconnaissance  work,  it  is  obviously  impossible  to  work  out  minor 
structures  and  to  detect  all  great  faults,  the  general  relations  may  be 
observed.  During  the  writer's  visit  to  the  Ferry  iron  property 
definite  paleontologic  data  were  obtained  which  tend  to  bring  the 
problem  nearer  solution. 
The  general  course  of  Provo  River  lies  along  the  division  between 
the  sandstone  and  quartzite  formations  whose  geologic  age  is  in  doubt 
and  the  overlying  limestone  formation.  This  great  sandstone  forma- 
tion, which  is  exposed  in  the  canyon  cut  by  the  North  Fork  of  the 
Provo,  and  in  the  canyon  of  the  main  Provo  River,  north  from  its 
junction  with  Soapstone  Gulch,  appears  to  underlie  a  gray,,  fossil- 
iferous  limestone.  From  croppings  of  this  limestone  on  the  Provo- 
Duchesne  divide  between    the   heads  of    Soapstone  and    Iron    Mine 
a  Emmons,  S.  F.,  U.  S.  Geol.  Explor.  40th  Par.,  vol.  2,  pp.  198-199,  201,  202. 
b  White,  C.  A.,  Ninth  Ann.  Rept.  TJ.  S.  Geol.  Survey,  1889,  pp.  687-688. 
