542  PRE-CAMBEIAN    GEOLOGY   OF    NORTH    AMERICA. 
series  contain  minute  oval  and  rounded  concretions  so  characteristic 
of  the  iron  formation  of  the  Animikie. 
Wilson,60  in  1903,  makes  a  geological  reconnaissance  about  Albany 
River.  Laurentian  and  Huronian  rocks  are  found.  The  latter  are 
similar  to  Lawson's  Keewatin  series.  The  broadest  belt  of  these  _ 
rocks  was  crossed  about  38  miles  (by  water)  above  Lac  Seul,  and 
extends  for  a  distance  of  about  20  miles.  A  second  narrow  belt  is 
crossed  at  the  Height-of-Land  portage  leading  into  Big  Portage  Lake 
from  the  waters  tributary  to  the  Wenassaga. 
Low,01  in  1903,  describes  the  geology  of  the  Nastapoka  Islands, 
Hudson  Bay.  The  rocks  forming  the  islands  are  as  follows,  in 
descending  order: 
Section  of  rocks  forming  Nastapoka  Islands,  Hudson  Bay. 
1.  Rusty-weathering,    dark-gray    siliceous    rock    containing 
ankerite   (carbonate  of  iron  and  magnesia)   and  mag- 
netite    20-100 
2.  Dark-gray  siliceous  rock  containing  magnetite  with  ^mall 
quantities  of  ankerite 50-250 
3.  Red  jaspilite  rich  in  hematite  ore 10-100 
4.  Red  jaspilite  poor  in   hematite  ore 5-20 
5.  Purple,    or    greenish-weathering,    dark-green    graywacke 
shales 10-70 
6.  Red  jaspilite  poor  in  hematite  ore 0-5 
7.  Light  greenish-gray  sandstone  and  shales 10-300 
8.  Fine-grained    dolomite 0-50 
There  is  a  general  dip  toward  the  west,  or  toward  the  sea,  of  5° 
to  15°.  There  are  north-south  faults,  the  upthrow  being  almost  on 
the  west  side,  with  the  result  that  the  rocks  appear  in  north-south 
ridges.  The  displacement  is  small  and  rarely  exceeds  100  feet. 
Another  system  of  faults  lies  transverse  to  the  first  system. 
Large  areas  of  similar  unaltered  sedimentary  rocks  occur  through- 
out the  peninsula  of  Labrador,  and  are  probably  the  equivalents  of 
certain  of  the  iron-bearing  series  above  Lake  Superior  and  of  those 
to  the  west  of  Hudson  Bay,  hand  specimens  from  these  localities 
being  undistinguishable.  On  former  maps  of  portions  of  the  penin- 
sula of  Labrador  the  areas  of  rocks  belonging  to  this  formation  have 
been  colored  as  belonging  to  the  Cambrian  formation,  and  in  the 
earlier  reports  on  this  region  the  rocks  were  thought  to  be  a  part  of 
that  system,  owing  to  their  unaltered  condition,  in  contrast  with  all 
the  other  rocks  of  that  vast  area,  which  were  either  crystalline  gran- 
ites and  other  irrupted  rocks  or  crystalline  schists  and  gneisses,  so 
completely  metamorphosed  as  to  have  lost  all  trace  of  their  original 
sedimentary  nature,  if  any  were  sediments.  These  highly  crystalline 
rocks  were  classed  as  Laurentian  or  Huronian  and  were  considered  to 
be  much  older  than  the  unaltered  rocks  of  the  so-called  Cambrian 
areas.    More  extended  and  closer  studv  of  both  the  unaltered  and  the 
