GYPSUM  AND  PLASTERS. 
GYPSUM  OF  THE  UNCOMPAHGRE  REGION,  COLORADO. 
By  C.  E.  SrEBENTIIAL. 
Location. — The  gypsum  measures  herein  described  are  located  on  the  west  side  of  the 
Grand  Canyon  of  Gunnison  River,  partly  in  Delta  County  .and  partly  in  Montrose  County, 
Colo.,  as  shown  on  the  accompanying  sketch  map  (fig.  16).  The  eastward  extension  of 
the  measures  across  the  canyon,  in  all  probability,  likewise  contains  extensive  deposits  of 
gypsum,  but  as  they  are  accessible  only  with  much  difficulty  from  the  west  side  of  the  river 
they  were  not  visited,  though  their  position  has  been  indicated  on  the  map. 
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Fig.  16.— Gypsum  measures  of  the  Uncompahgre  region. 
Structure. — From  the  intake  of  the  Gunnison  tunnel  the  river  flows  northwestward  for 
18  miles  and  then  due  north  for  12  miles,  thus  skirting  the  southwest  and  west  edges  of 
the  Mesa  Inclinada.  This  course  approximately  coincides  with  the  asymmetric  anticline 
which  changes  the  gentle  northeast  dip  of  the  mesa  to  a  steeper  southwest  dip  in  the  terri- 
tory bordering  the  18  miles  of  canyon  on  the  southwest  and  to  a  west  dip  in  the  lower  12 
miles  of  its  course.     The  Mesa  Inclinada  is  a  dip  or  structural  slope  of  between  2°  and    3°, 
401 
