LIME    INDUSTRY    OF    KNOX    COUNTY,   ME. 
397 
were  deposited  on  the  ocean  bottom  somewhat  earlier  than  the  limestones,  which  in  most 
places  they  immediately  underlie.  In  the  region  southwest  of  Rockland,  however,  there 
is  a  local  development  between  the  schists  and  the  limestone  of  a  considerable  thickness 
of  quartzite  and  a  thin  bed  of  talcose  limestone.  Fig.  15,  which  shows  a  section  from  north- 
west to  southeast  across  the  limestone  belts  southwest  of  Rockland,  is  intended  to  illus- 
trate the  general  relations  outlined  above;  it  is  not  drawn  to  scale  and  is  purely  diagram- 
matic, the  folding  being  in  places  even  closer  than  shown.  The  sedimentary  rocks  under- 
lying the  limestone  are  represented  by  A  in  the  figure,  the  locally  developed  quartzite  and 
talcose  limestone  beds  not  being  separately  shown.  Among  the  limestones  several  varie- 
ties are  indicated,  B=magnesian  limestone  or  dolomite,  C=the  so-called  "hard  rock"  of 
the  quarrymen,  D=impure  limestone,  and  E=the  "soft  rock"  of  the  quarrymen.  These 
limestones  form  a  broad  down  fold  (synclinorium),  which  is  itself  divided  into  a  number 
of  smaller  folds,  both  up  folds  (anticlines)  and  down  folds  (synclines).  A  comparison  of 
this  cross  section  with  fig.  14  shows  that,  considered  as  a  whole,  the  limestone  occurs  as  a 
broad  trough  made  up  of  numerous  smaller  folds.  The  main  large  fold  is  not  perfectly 
symmetrical,  its  western  side  being  relatively  steep;  as  a  result,  the  limestone  terminates 
abruptly  on  the  west.  To  the  southeast,  however,  we  have  a  number  of  small  outlying 
limestone  troughs  (see  fig.  14),  which  represent  the  minor  foldings  of  the  main  trough 
and  show  that  its  eastern  side  has  a  much  gentler  slope.  One  of  these  outlying  troughs 
is  shown  in  fig.  15  at  B'. 
c'e"     e'o'       e      c 
Fig.  15.— Diagrammatic  geologic  section  across  the  principal  limestone  belt  southwest  of  Rock 
land,  Me. 
The  position  of  the  magnesian  limestone  at  the  base  of  the  limestone  series  is  definitely 
determined  by  field  studies,  but  the  relative  position  and  thickness  of  the  "hard  rock," 
the  impure  limestone,  and  the  "soft  rock"  are  not  known,  the  relations  having  been  obscured 
by  the  folding  and  its  attendant  alteration  of  the  rocks.  The  reader  is  therefore  especially 
cautioned  against  drawing  any  inferences  from  the  diagram  in  regard  to  the  sequence  or 
relative  thickness  of  these  three  types  of  rock. 
MAGNESIAN   LIMESTONE  OR  DOLOMITE. 
The  presence  of  magnesian  limestone  below  the  other  varieties  is  shown  particularly 
from  a  stud}?-  of  the  limestone  belts  lying  southeast  of  the  large  Rockland  belt  (see  fig.  14). 
These  outlying  belts  are  usually  only  100  to  200  feet  in  width  and  manifestly  can  n  pie- 
sent  only  the  lower  part  of  the  limestone  series,  as  is  brought  out  in  fig.  15  at  B'.  In  each 
of  these  outlying  areas  the  bulk  of  the  rock  is  found  to  be  a  magnesian  limestone,  a  charac- 
teristic which  may  be  recognized  in  the  field  from  the  fact  that  the  rock  effervesces  feebly  or 
not  at  all  when  dilute  muriatic  acid  is  applied.  This  rock  is  usually  light  gray  to  pure  while 
in  color  and  veiy  fine  grained.  It  has  been  quarried  at  a  number  of  places  and  is  usually 
used  for  pulp  purposes.  At  the  Gay  farm,  about  2  miles  southwest  of  Rockland  along 
the  railroad,  one  of  these  small  troughs  of  magnesian  limestone  was  formerly  worked  l>\ 
the  Rockland-Rockport  Lime  Company.  Analysis  No.  I  of  the  table  (p.  — )  is  of  a  limestone 
from  this  quarry.  The  rock  was  of  uneven  grain  and  apt  to  be  high  in  silica  and  silicates. 
The  quarry  was  abandoned,  although  the  supply  along  the  trend  of  the  deposit  was  by  no 
means  exhausted. 
The  quarry  1  mile  southwest  of  Rockland,  on  the  east  side  of  "the  Marsh,"  now  being 
operated  by  Mr.  S.  P.  Dunton  for  the  McLoon  &  Stover  Lime  Company,  is  located  on 
Bull.  285—06 26 
