STONE.] 
OIL    AND    GAS    FIELDS    OF    GREENE    COUNTY,   PA. 
397 
tion  includes  the  Pittsburg-,  Redstone,  Sewickley,  Uniontovvn,  and 
Waynesburg  coals;  the  Ben  wood  and  Waynesburg  limestones  are  its 
most  conspicuous  members.  That  the  Pittsburg  coal  underlies  all  of 
this  field  is  proved  by  the  logs  of  a  large  number  of  deep  wells.  The 
Redstone  and  Uniontown  coals  are  thin  and  have  no  economic  value. 
The  Sewickley  coal  varies  from  20  inches  to  5  feet  in  thickness,  and  is 
mined  in  the  southeast  part  of  the  county.  Ben  wood  limestone  is  the 
new  name  proposed  by  Prof.  1.  C.  White  for  the  100  feet  or  more  of 
Fig.  11. — Sketch  map  of  eastern  Greene  County,  Pa. 
calcareous  rocks  known  as  the  Great  limestone,  which  lie  between 
the  Sewickle}^  and  Uniontown  coals.  The  Waynesburg  coal  is  about 
5  feet  thick,  and  is  mined  in  many  places  for  local  use. 
Dunkard  formation. — Above  the  Monongahela  formation  is  a  series 
of  comparatively  soft  rocks  extending  from  the  roof  shales  of  the 
Waynesburg  coal  to  the  topmost  beds  of  the  Appalachian  region.  In 
the  eastern  half  of  Greene  County  the  greatest  thickness  of  the  forma- 
