156  PRE-CAMBKTAN    GEOLOGY   OP    NORTH   AMERICA. 
are  shown  to  be  mashed  basic  eruptives.  The  granites  and  dike  mate- 
rials are  similar  in  essential  features  to  the  corresponding  rocks  of 
the  Northern  Complex.  The  granites  are  younger  than  the  schists, 
since  dikes  from  them  intrude  the  schists.  The  Palmer  gneisses  occur 
only  on  the  borders  of  the  granite  areas,  between  these  and  the  Mar- 
quette sedimentaries,  and  are  apparently  in  most  cases  extremely 
mashed  phases  of  the  granites. 
The  isolated  areas  of  the  Fundamental  Complex  within  the  Algon- 
kian  are  chiefly  gneissoid  granites  and  schistose  greenstones  that  dif- 
fer in  no  essential  respect  from  the  corresponding  rocks  of  the  North- 
ern Complex  and  the  Southern  Complex. 
The  Lower  Marquette  series  is  composed  of  the  following  forma- 
tions, given  from  the  base  upward :  The  Mesnard  quartzite,  the  Kona 
dolomite,  the  Wewe  slate,  the  Ajibik  quartzite,  the  Siamo  slate,  and 
the  Negaunee  iron  formation.  There  is  no  break  between  these  for- 
mations; the  series  is  a  continuous  one. 
The  Mesnard  quartzite  is  chiefly  a  metamorphosed  sandstone. 
However,  at  the  bottom  of  this  formation  is  a  conglomerate,  which  in 
grading  into  the  sandstone  passes  through  slate  and  graywacke.  The 
conglomerate  is  basal,  being  composed  of  detritus  from  the  Basement 
Complex.  At  the  top  of  the  formation  is  a  slate.  The  Mesnard 
quartzite  is  the  first  deposit  of  the  westward-transgressing  Lower 
Marquette  sea.  By  the  time  the  sea  had  advanced  westward  a  short 
distance  upon  the  Marquette  district  the  Kona  dolomite  began  to  be 
formed,  and  hence  the  Mesnard  formation  is  confined  to  the  eastern 
part  of  the  district.  The  thickness  of  the  Mesnard  quartzite  is  from 
150  to  670  feet. 
The  Kona  dolomite  is  largely  an  altered  limestone,  but  it  includes 
interst ratified  layers  of  slate,  graywacke,  and  quartzite,  with  grada- 
tion phases  between  these  and  the  pure  dolomite.  The  Kona  dolo- 
mite, like  the  Mesnard  quartzite,  is  confined  to  the  eastern  part  of  the 
district.  The  dolomite  varies  through  a  slate  into  the  Mesnard 
quartzite  below,  and  by  a  lessening  of  the  calcareous  constituent  grad- 
ually passes  into  the  Wewe  slate  above.  The  thickness  is  from  425  to 
1,375  feet. 
The  Wewe  slate  is  chiefly  a  metamorphosed  mudstone,  but  with 
the  slates  are  conglomerates,  quartzites,  graywackes,  mica  slates,  and 
mica  schists.  The  Wewe  slate,  like  the  two  previous  formations,  is 
confined  to  the  eastern  part  of  the  district.  The  formation  grades 
into  the  Kona  dolomite  below  and  the  Ajibik  quartzite  above.  The 
thickness  is  from  550  to  1,050  feet. 
The  Ajibik  quartzite  is  mainly  a  metamorphosed  sandstone,  which 
in  different  parts  of  the  district,  depending  upon  various  conditions, 
has  been  transformed  into  quartzite,  cherty  quartzite,  ferruginous 
quartzite,  ferruginous  cherty  quartzite,  quartz  rock,  and  quartzite 
