336 
CONTRIBUTIONS    TO   ECONOMIC    GEOLOGY,  1906,  PART    I. 
Measures)  and  the  Pottsville  formation. 
follows: 
The  succession  of  rocks  is  as 
L30  feel 
Relativi  positions  of  beds  in  Allegheny  and  Pottsville  formations  in  Clarion  quadranglM 
Pennsylvania. 
Allegheny  formation: 
( !<  lal  (Upper  Freeport) 
Plastic  clay 
Limestone 
Flint  clay 
Shale  and  sandstone 
( 5oal    Lower  Freeporl  I 
Plastic  clay 
Limestone 
Shale  and  Bandstone 
* !oal  1 1  Ipper  Kittanning) 
Plastic  clay 
Shale  and  Bandstone 
Coal 
Plastic  clay 
Shale  and  sandstone 
Coal  i  Middle  Kittanning) 
Plastic  clay 
Shale.... 
Coal  i  Lower  Kittanning) 
Plastic  clay 
I  loal    Lower  Kittanning?  I 
Flint  and  plastic  clay 
shale  and  Bandstone 
Limestone 
Sandstone 
Shale 
Coal  i  Upper  Clarion  l 
Plastic  clay  and  shale 
Coal  I  Lower  Clarion  
Plastic  clay 
Shale..... 
<  oal    Brookville  
Clay 
110   feet. 
Ii()   feet. 
Pottsville  formation: 
Sandstone  I  Eomewood  . 
shale,  coal,  plastic  and  tlini    ?   clay  i  Mercer). 
Sandstone   <  Sonnoquenessing 
The  figures  showing  the  thickness  of  the  groups  represent  a  fair 
average  but  are  not  intended  to  be  final. 
A  glance  at  the  table  shows  that  eleven  clay  horizons  arc  asso- 
ciated with  the  same  number  of  coal  horizons,  the  clays  underlying 
the  coals.  Two  and  possibly  three  of  the  clay  beds  contain  flint  clay. 
It  will  be  noted  that  two  of  the  coals  are  designated  Lower  Kittan- 
