ADIRONDACK    MOUNTAINS.  621 
direction  of  the  bedding  may  therefore  be  determined  in  parts  of  tin- 
region  by  the  contacts  of  the  layers  of  different  lithological  charac- 
ters. So  far  as  observed,  the  schistosity  of  the  series  corresponds 
with  the  bedding. 
Between  the  marble-bearing  gneisses  are  gneisses  free  from  lime- 
stone, which  are  red  or  gray  and  orthoclastic.  The  broader  of  these 
areas  are  on  the  southern  and  western  sides  of  the  Adirondacks. 
At  many  places  the  contact  of  the  marble  with  the  gneiss  is  of  an 
extraordinary  character.  The  plane  between  them  is  one  of  great 
irregularity.  Interstratified  with  the  limestone  are  gneissic  or  peg- 
matitic  layers.  As  a  result  of  a  strong  movement,  at  many  localities 
the  interstratified  gneiss  and  pegmatite  have  been  broken  into  frag- 
ments which  are  contained  within  the  marble,  thus  producing  auto- 
clastic  rocks  which  in  some  places  simulate  remarkably  erosion  con- 
glomerates. Between  the  breccia  and  the  interlaminated  gneiss,  peg- 
matite, and  marble  there  are  all  gradations.  The  marble  associated 
with  or  containing*  the  disrupted  fragments  of  the  gneiss  in  some 
places  shows  no  evidence  whatever  of  movement,  being  massive  and 
coarsely  crystalline.  The  included  fragments  and  gneiss  adjacent, 
on  the  other  hand,  give  all  the  evidences  of  deformation. 
The  gabbros  and  their  associated  phases,  anorthosite,  syenite,  and 
granite,  are  all  intrusive  into  the  entire  sedimentary  series.  The  dia- 
base dikes  are  the  latest  intrusives  of  the  district. 
Correlation. — The  sedimentary  gneisses,  limestones,  and  quartz- 
ites  have  been  called  the  "  Oswegatchie  series  "  by  Smyth.  Following 
the  conclusions  of  the  international  committee  in  190C),  there  is  little 
doubt  that  this  series  may  be  safely  correlated  with  the  Grenville 
series  of  the  original  Laurentian  and  Hastings  districts.  This  being 
the  case,  the  term  Grenville  has  priority  and  the  name  w>  Oswegatchie  " 
is  unnecessary.  When  it  is  determined  where  the  Grenville  -erics 
of  the  Laurentian  district  belongs  with  reference  to  the  Archean  or 
the  Algonkian,  this  will  solve  in  large  measure  the  problem  of  corre- 
lation of  the  Adirondack  Grenville.  It  is  regarded  as  probable  by 
Adams  that  the  "  Grenville  "  limestone  represents  mere  shreds  of  what 
was  once  a  continuous  sedimentary  formation  that  covered  the  region 
and  was  continuous  with  the  less  metamorphosed  Hastings  series. 
Miller  and  Knight,  on  the  other  hand,  find  the  Grenville  series  to 
be  unconformablv  below  at  least  part  of  the  Hastings,  also  containing 
limestone,  and  above  basic  igneous  Hows.  They  conclude  thai  the 
"Grenville"  limestone  shows  the  same  relations  to  the  basic  igneous 
rocks  as  do  the  Keewatin  iron-bearing  formations  to  the  Keewatin 
greenstones  of  the  Lake  Superior  region,  suggesting  correlation  of  the 
Grenville  with  the  Keewatin. 
The  mapping  of  the  Adirondack  region  has  not  yet  discriminated 
a  later  sedimentary  series,  and  the  whole  is  therefore  mapped  as 
unclassified  pre-Cambrian. 
