888  PKE-CAMBRIAN    GEOLOGY    OF    NORTH   AMERICA. 
Ska  jit  and  the  Birch  Creek  with  the  Totsen.  If  this  proves  to  be 
the  case  and  the  Ska  jit  is  Silurian,  as  supposed,  the  Birch  Creek 
and  Totsen  would  fall  into  the  Cambrian  or  pre-Cambrian. 
Mendenhall,0  in  his  exploration  of  the  Allen  and  Kobuk  rivers, 
not  attempting  to  differentiate  the  semicrystalline  rocks  which  he 
encountered  in  his  rapid  journey,  grouped  them  together  under  the 
term  "  Metamorphic  complex."  In  this  group  are  included  schists  of 
various  types,  limestones,  quartzites,  and  greenstones.  The  lithology 
is  that  of  the  older  terranes  of  other  parts  of  Alaska,  but  Menden- 
hall was  unable,  to  ascertain  the  succession  within  the  complex.  The 
group  was  traced  westward  to  Kotzebue  Sound,  and  was  regarded 
by  Mendenhall  in  a  broad  way  as  the  equivalent  of  the  metamorphic 
terranes  of  Seward  Peninsula. 
Nearly  the  entire  bed-rock  series  of  Seward  Peninsula  is  older  than 
the  Devonian.  The  terranes  vary  from  highly  crystalline  schists  to 
those  which  are  practically  unaltered.  The  stratigraphic  succession 
is  now  fairly  well  determined,  though  only  one  formation  has  re- 
ceived a  definite  assignment  to  the  time  scale  on  paleontologic  evi- 
dence. The  accumulation  of  geologic  data  regarding  this  province 
has  gone  on  intermittently  since  1899,  but  the  close  of  the  season  of 
1903  saw  the  completion  of  the  reconnaissance  surveys  throughout 
the  peninsula.  The  general  succession  is  as  follows,  beginning  with 
the  oldest:  Mica  schist  and  crystalline  limestone  beds  (Kigluaik 
group),  graphitic  quartzites  (Kuzitrin  group),  these  unconform- 
ably(?)  overlain  by  mica  schists,  then  massive  limestones,  and  then 
mica  schists  (Nome  group).  The  massive  limestone  in  this  latter 
subdivision  carries  Silurian  fossils  and  has  been  called  the  Port 
Clarence  limestone.  The  following  discussion  is  based  primarily 
on  the  writer's  own  field  work  in  1900,6  modified  somewhat  by 
Collier,  who  extended  the  reconnaissance  work  in  1901 c  and  again  in 
1903/z  Other  contributor's  have  been  Mendenhall,  who  studied  the 
geology  of  the  southeastern  part  of  the  peninsula  in  1900,e  and  in 
1901  f  touched  the  northern  coast  during  an  exploration  already  re- 
ferred to;  and  Moffit,  who  completed  the  reconnaissance  mapping  of 
the  northeastern  portion  of  the  peninsula  in  1903.^ 
°  Mendenhall,  W.  C,  A  reconnaissance  from  Fort  Hamlin  to  Kotzebue  Sound :  Prof, 
Paper  U.   S.  Geol.   Survey  No.   10,  1902,  pp.   31-36. 
b  Brooks,  Alfred  H.,  A  reconnaissance  of  the  Cape  Nome  and  adjacent  gold  fields  of 
Seward  Peninsula,  contained  in  a  special  publication  of  the  U.  S.  Geol.  Survey,  entitled 
Reconnaissances  in  the  Cape  Nome  and  Norton  Bay  regions,  Alaska,  1900,  pp.  27-41. 
.  c  Collier,   A.   J.,   A  reconnaissance  of  the  northwestern  portion   of  Seward  Peninsula  : 
Prof.   Paper  U.   S.  Geol.  Survey  No.  2,  1902,  pp.   16-24. 
d  Collier,  A.  J.,  Hess,  F.  L.,  Smith,  P.  S.,  and  Brooks,  A.  H.,  Gold  placers  of  parts  of 
Seward  Peninsula,  Alaska  :  Bull.  U.  S.  Geol.  Survey  No.  328,  1908. 
e  Mendenhall,  W.  C,  A  reconnaissance  in  the  Norton  Bay  region,  Alaska,  in  1900,  con- 
tained in  a  special  publication  of  the  U.  S.  Geol.  Survey,  entitled  Reconnaissances  in  the 
Cape  Nome  and  Norton  Bay  regions,  Alaska,  1900,  pp.  199-205. 
f  Prof.  Paper  U.  S.  Geol.  Survey  No.  10,  1902. 
s  Moffit,  F.  11.,  The  Fairhaven  gold  placers  of  Seward  Peninsula  :  Bull.  U.  S.  Geol.  Survey 
No.  247,  1905. 
