(LAVS  AND    SHALES    OF   SOUTHWESTERN 
CAMBRIA  COUNTY,  PA. a 
By  W.  C.  Phalen   and   Lawrence  Martin. 
INTRODUCTION. 
Area. — The  area  here  considered  is  the  Johnstown  quadrangle  of 
the  United  Stales  Geological  Survey,  comprising  228  square  miles 
in  southwest-central  Pennsylvania.  Though  mostly  in  Cambria 
Count}  .  it  includes  small  parts  of  Indiana,  West  morelaud,  and  Somer- 
set counties. 
Geology. — The  rocks  thai  outcrop  in  this  district  are  mostly  of 
the  Carboniferous  system,  but  a  few  hundred  feet  (400±)  of  Devonian 
rocks  are  present.  Of  the  Carboniferous  rocks  only  those  of  the 
Pennsylvanian  series  are  of  interest,  for.  except  the  Pleistocene  and 
later  clays,  all  the  valuable  clay  deposits  seem  to  be  confined  to 
this  series.  As  developed  in  this  area  the  Pennsylvanian  series  com- 
prises the  Pottsville,  the  Allegheny,  and  perhaps  all  or  nearly  all 
of  the  Conemaugh  formation — in  all,  about  1,200  feel  of  beds. 
These  formations  correspond  to  the  Pottsville  conglomerate  or  Mill- 
stone grit,  the  Lower  Productive,  and  Lower  Barren  Coal  Measures, 
respectively,  of  the  Second  Geological  Survey  of  Pennsylvania. 
THE   CLAYS. 
The  clay  materials  of  this  region  are  flinl  clays,  plastic  clays 
(including  some  fire  clays',  and  shales. 
GEOLOGICAL    POSITION    OF   THE    (LAYS. 
Flint  clays  are  Inn nd  al  three  and  possibly  more  horizons.  The 
highest  flint  clay  occurs  in  the  Conemaugh  formation  and  varies  in 
position  in  the  Johnstown  district  from  50  to  100  feet  above  the 
Upper  Freeport  coal  (known  also  as  the  "E,"  Coke  Yard,  "Four- 
foot,"  and  Lemon  seam),  and  usually  lies  near  the  top  of  the  Mai  toning 
sandstone.  In  the  Blacklick  Creek  district,  west  and  southwest  of 
Wehrum,  a  flint  clay  has  been  observed  at  many  places  in  a  similar 
position  with  reference  to  the  Mahoning  sandstone  and  is  probably 
to  be  correlated  with  the  flint  clay  occurring  about  Johnstown. 
a  These  notes  Are  preliminary  in  nature     A  more  detailed  account  of  the  clay  resources  of  the  .'oh  ns- 
town  quadrangle  will  be  published  later. 
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