281 
Stratigraphy. — The  oldest  rock  exposed  in  the  area  considered  is  probably  the  coarse  red 
conglomerate  which  outcrops  in  a  narrow  belt  at  the  east  base  of  the  Gunnison  Plateau  in 
the  vicinity  of  Wales.  This  rock  is  composed  of  rounded  pebbles  of  quartzite  and  subor- 
dinate limestone  and  dips  steeply  eastward  beneath  the  "wash"  of  the  valley.  It  is 
limited  on  the  west  by  the  fault  which  separates  it  from  the  low,  westward-dipping  Tertiary 
Istrata  of  the  Gunnison  Plateau.  No  fossils  have  been  found  in  the  conglomerate,  but  on 
;lithologic  grounds  it  is  provisionally  correlated  with  the  great  mass  of  conglomerate  west  of 
the  Sanpete-Sevier  Valley  which  underlies  Eocene  and  unconformably  overlies  Paleozic 
strata.  Its  age  is  probably  Mesozoic  and  possibly  may  prove  to  be  Cretaceous.  This  con- 
i glomerate  is  unimportant  so  far  as  the  coal  to  be  described  is  concerned. 
The  coal-bearing  Cretaceous  rocks  of  Carbon  County  outcrop  along  the  eastern  scarp  of  the 
Wasatch  Plateau  and  are  conformably  overlain  by  a  considerable  but  unmeasured  thickness 
of  massive  buff  sandstones  which  locally  cap  the  plateau,  and  outcrop  in  the  valleys  of  the 
:  creeks  that  have  cut  deeply  into  its  western  flanks.     This  sandstone  on  the  Wasatch  Plateau 
}  is  overlain  apparently  conformably  by  fresh-water  deposits  of  Eocene  age,  but  different  sec- 
!  tions  show  such  variable  conditions  at  the  base  of  the  known  Tertiary  that  true  conformity 
,  in  the  sense  of  a  succession  of  widespread,  uniform,  uninterrupted  deposits  does  not  exist. 
In  the  vicinity  of  Sterling  there  is  a  distinct  unconformity  marked  by  flat-lying  Tertiary 
beds  resting  on  highly  inclined  sandstones,  but  here  the  sandstone  is  separated  from  the 
main  mass  on  the  plateau  by  faulting,  and,  though  probably  the  same,  it  is  not  certain  that 
they  are  one  and  the  same  bed.     A  few  fragments  of  leaves  too  obscure  for  identification  are 
the  only  fossils  that  have  been  found  in  this  sandstone  on  the  plateau,  but  in  the  sandstone  of 
the  fault  block  in  which  the  Sterling  coal  occurs  a  number  of  plants  have  been  found,  among 
which  F.  H.  Knowlton  recognizes  Sabal  (?)  cf.  Sabalites  Grayanus,  Asimina  eocenica  (?) 
Lesq.,  and  Salix  sp.  (?),  from  which  he  concludes  that  their  age  is  probably  Laramie. 
Tertiary  rocks  cover  the  greater  part  of  the  area  here  considered.  They  outcrop  on  the 
summit  and  western  flanks  of  the  Wasatch  Plateau  and  occupy  much  of  the  summit  and 
eastern  part  of  the  Gunnison  Plateau,  and  also  form  low  ridges  in  Sanpete  Valley.  These 
Tertiary  beds  are  light  colored,  consisting  of  drab  or  locally  red  shales,  with  interbedded  thin 
limestone  and  sandstone  layers,  and  massive,  fine-textured,  light-gray  limestone  that 
weathers  white.  The  stratigraphy  is  characteristically  varied,  even  adjacent  sections  being 
rarely  alike.  The  thickness  of  the  beds  is  at  least  2,000  feet.  Numerous  fresh-water 
genera,  including  Sphserium,  Planorbis,  Physa,  Goniobasis,  and  Vivipara,  identified  by  W.  H. 
Dall,  occur  in  these  rocks,  which  are  referred  to  the  Wasatch  stage  of  the  Eocene. 
The  Tertiary  sediments  in  the  ridges  in  Sanpete  Valley,  referred  to  above,  dip  slightly  to 
the  west  and  are  separated  from  the  Wasatch  beds  just  described  by  Quaternary  deposits. 
The  rocks  of  the  valley  undoubtedly  are  younger  than  those  on  the  plateau,  but  whether  they 
conformably  overlie  the  Wasatch  strata  was  not  determined.  Cope  a  named  them  the  Manti 
beds  and  considered  their  age  to  be  Middle  Eocene,  corresponding  with  the  Wind  River 
stage.     They  contain  well-preserved  specimens  of  fishes,  turtles,  etc. 
Sanpete  Valley  is  underlain  by  a  considerable  but  unknown  thickness  of  gravel,  sand,  and 
clay,  derived  from  the  adjacent  highlands  and  deposited  to  a  large  extent  at  least  under  sub- 
aerial  conditions.  This  valley  filling  is  more  than  600  feet  thick,  as  shown  by  a  well  near 
Ephraim . 
COAL. 
Wales  coal— The  Wales  coal  mine  is  in  Wales  or  New  Canyon,  about  2  miles  west  of 
the  town  of  Wales,  at  the  foot  of  the  Gunnison  Plateau.  The  coal  occurs  near  the  base 
of  the  Eocene  there  exposed,  where  the  following  generalized  section  of  Wasatch  beds  was 
obtained: 
a  Cope,  E.  D.,  Am.  Naturalist,  vol.  14,  p.  303. 
