THE    CORDILLERAS.  889 
The  Kigluaik  group  has  been  described  by  the  writer  as  made  up  of 
highly  crystalline  limestones  and  mica  schists,  cut  by  many  stocks  and 
dikes  of  massive  granite.  Collier's  further  investigations  have  shown 
that  the  group  embraces  some  gneissoid  rocks  and  some  highly 
graphitic  schists.  These  rocks  are  succeeded  apparently  conformably 
by  the  Kuzitrin,  typically  made  up  of  a  highly  graphitic  quartzite. 
This  rock  subdivision  has  not  been  recognized  throughout  the  area,  and 
may  have  in  part  been  removed  by  erosion  before  the  deposition  of  the 
succeeding  beds,  which  are  apparently  unconformable. 
The  next  horizon  is  a  great  group  of  rocks  of  highly  diverse  litho- 
logical  character,  called  the  Nome  group.  A  considerable  thickness  of 
mica  schists,  containing  quartz  and  some  albite,  forms  the  basal  mem- 
ber of  this  group,  which  is  succeeded  by  massive  limestone  that  is 
in  some  places  semicrystalline.  This  calcareous  member  lias  been 
called  the  Port  Clarence  limestone  and  is  of  Silurian  age.  It  may 
prove  to  be  the  equivalent  of  the  Fortymile  group  and  the  Skajit 
formation  and  suggests  that  the  Kuzitrin  or  Kigluaik,  or  both,  may 
be  synchronous  deposits  with  the  Birch  Creek  schist  and  Totsen  group. 
METAMORPHOSED    PALEOZOIC    AND    POST- PALEOZOIC    ROCKS. 
It  is  desirable,  before  closing  this  discussion,  briefly  to  pass  in  review 
the  evidence  by  which  certain  of  the  metamorphosed  terranes  are 
assigned  to  the  Paleozoic  and  j^ounger.  Four  belts  of  these  younger 
met  amorphic  rocks  are  indicated  on  the  map.  The  first  stretches 
through  southeastern  Alaska  and  probably  forms  the  bed  rock 
throughout  the  greater  part  of  the  unexplored  St.  Elias  Range.  It 
has  been  identified  along  the  lower  Copper  River  valley  and  in  the 
Chugach  Mountains,  and  then,  bending  to  the  southwest,  forms  the 
backbone  of  the  Kenai  Peninsula  of  southeastern  Alaska.  Silurian," 
Devonian,  Carboniferous,  and  Lower7'  Cretaceous  fossils  have  been 
found  in  these  metamorphic  rocks  of  southeastern  Alaska.  The  meta- 
morphic  rocks  of  what  appears  to  be  the  western  end  of  the  same  belt 
have  thus  far  yielded  no  fossils,  and  they  have  been  variously  assigned 
to  the  Paleozoic  c  and  the  Mesozoic.  The  intensely  folded  rocks  of  the 
Chugach  Mountains  may  include  some  pre-Cambrian  sediments,  but 
of  this  no  evidence  has  yet  been  found. 
a Brooks,  Alfred  li..  Preliminary  reporl  on  the  Ketchikan  mining  district,  Alaska  :  Prof. 
Paper  ['.  s.  Geol.  Survey  No.   1,    L902,  pp.   Hi  31. 
6  Wright,  Fred  E.  and  C.  W..  unpublished  manuscript. 
"Russell,  I.  C,  Expedition  to  Mount  si.  Elias:  Nat.  Geog.  Mag.,  vol.  3,  1890.  pp.  17". 
174.  Schrader,  P.  C,  A  reconnaissance  of  a  part  of  Prince  William  Sound  and  Copper 
River  districts  in  1898  :  Twentieth  Ann.  Rept.  U.  S.  Geol.  Survey,  pi.  7.  11)00,  pp.  408  I  LO. 
Schrader,  P.  ('.,  and  Spencer,  A.  ('..  The  geology  and  mineral  resources  of  a  portion  of  the 
Copper  River  district,  a  special  publication  of  the  0".  S.  Geol.  Survey.  1901,  pp.  •"■  I  37. 
Mendenhall,  w.  C,  A  reconnaissance  from  Resurrection  Bay  to  the  Tanana  River:  Twen- 
tieth Ann.  Rept.  1'.  S.  Geol.  Survey,  pt.  7.  1900,  pp.  265-340.  Emerson,  B.  K..  Harriman 
Alaska  Expedition,  vol.  4,  New  York,  idol',  pp.  11-54.  Martin,  G.  *'..  The  petroleum  fields 
of  the  Pacific  coast  of  Alaska  :  Bull.  U.  S.  Geol.  Survey  No.  250,  L905,  pp  64.  Mendenhall, 
W.  C,  The  geology  of  the  central  Copper  River  region:  Prof.  Paper  I'.  S.  Geol.  Survey 
No.   41,   1905,    pp.    L33. 
