DURANGO-GALLUP    COAL    FIELD,    COLORADO-NEW     MEXICO.        L;.~;  1 
The  coal  in  I  his  bed  is  of  good  quality  and  has  been  mined  for  local  use.  The  rocks  arc 
►verturned  and  dip  cast,  toward  the  mountain,  at  an  angle  of  aboul  70°. 
i  The  same  coal  bed  has  been  opened  by  the  roadside  near  Senorita,  2  miles  south  of  the 
iho\ c-mentioned  locality,  and  mined  by  the  Juratrias  and  other  copper  companies.  The 
:oa]  was  used  for  steaming  and  smelting,  as  well  as  for  domestic  purposes.  It  is  of  good 
iUiulily  and  is  reported  to  have  given  general  satisfaction.  The  coal  bed  is  aboul  6  feet 
thick  and  inclines  steeply  to  the  east  at  an  angle  of  about  70°,  the  measures  being  over- 
turned, as  at  ( topper  City. 
South  of  Senorita  the  coal  outcrops  at  intervals  for  a  distance  of  several  miles,  nearly  to 
■the  place  where  the  Mesaverde  formation,  still  upturned  and  on  edge,  disappears  below 
bverlying  younger  formations.  Beyond  this  place  the  formation  seems  to  extend  a  long 
distance  to  the  south  and  probably  carries  the  coal  beds  that  are  reported  west  of  Albu- 
querque. About  a  mile  north  of  the  place,  where  the  Mesaverde  formation  disappears,  it 
is  unconformably  in  contact  on  the  west  with  coal-bearing  rocks,  which  lie  nearly  Hat  and 
are  younger  than  the  Mesaverde  and  form  the  Chico  Arroyo  district,  described  below. 
The  contact  between  these  two  formations  is  due  to  faulting. 
CHICO    ARROYO    DISTRICT. 
The  Chico  Arroyo  district  extends  from  the  western  base  of  the  Sierra  Nacimiento, 
between  Senorita  and  San  Miguel,  soul  h  west  ward  nearly  to  San  Mateo  and  Mount  Taylor, 
a  distance  of  nearly  60  miles. 
The  coal  beds  are  associated  with  clay,  carbonaceous  shale,  and  sandstone,  which  aggre- 
gate a  thickness  of  from  2,000  to  3,000  feet,  and  are  regarded  as  a  great  coal-bearing  group; 
but,  as  previously  noted,  they  are  faulted  in  contact  with  the  Mesaverde  formation  on  the 
east ,  am!  so  it  was  impossible  during  this  reconnaissance  to  determine  their  exact  relal  ions 
and  geologic  horizon.  Some  invertebrate  fossils  were  found  in  them,  however,  which  indi- 
cate that  they  belong  above  the  Mesaverde  formation,  in  the  upper  part  of  the  Montana. 
I  lence,  on  account  of  its  relat  ive  posit  ion  in  the  series,  the  group  is  here  designated  the  upper 
coal  group  of  the  Montana  formation. 
Throughout  the  district  the  beds  in  general  dip  about  3°  in  a  direction  slightly  west,  of 
noil  h.  The  coals  are  exposed  mainly  in  1  he  scarp  formed  by  the  southeastern  edges  of  the 
rocks  along  Rio  Puerco  and  the  head  of  Torreones  Arroyo  and  underlie  the  Chacra  Mesa 
and  the  lava-capped  plateau  of  I  he  Sierra  Chivato.  The  following  seel  ions  were  measured 
at  separate  localities  well  distributed  throughout  the  districl  and  give  a  fair  idea  of  the 
character  of  the  coal  beds  of  this  group: 
Section  ofcoalbed  in  the  mesa  west  of  Rio  Puerco,  15  miles  north-northeast  of  Cabezon,  N.  Mex. 
Ft.  In. 
Sandstone 3 
Shale 3 
Coal '■> 
Shale,  brown  carbonaceous '    '^ 
Section  of  coal  bed  ■!  miles  abovi  mouth  oj  Arroyo  dt  los  Torreones,  10  miles  west-northwest  oj 
( 'ah,  ion,  V.   Mex. 
Ft.  In. 
Shale 2 
Coal 2  6 
Coal,  bony 3 
Shale 1  s 
Coal -    x  8 
Shale 5 
