692       *  PRE-CAMBRIAN    GEOLOGY    OF . NORTH   AMERICA. 
rite,  jasper,  crystalline  limestone,  dolomite,  and  igneous  rocks.  Crys- 
talline limestone  occurs  in  Chilton  County.  It  is  succeeded  in  appa- 
rent conformity  by  semicrystalline  rocks  15,000  to  20,000  feet  in 
thickness. 
Schmitz,103  in  1884,  describes  a  metamorphic  region  in  Alabama  as 
covering  the  whole  or  parts  of  counties  Chilton,  Coosa,  Talladega, 
Calhoun,  Cleburne,  Lee,  Tallapoosa,  Elmore,  Clay,  Randolph,  and 
Chambers,  with  about  5,000  square  miles  of  area.  The  rocks  of  this 
region  are  partly  metamorphosed  Lower  Silurian  rocks  (Calciferous, 
Potsdam,  and  Acadian),  partly  Upper  Azoic  rocks  (Huronian),  and 
perhaps  partly  Lower  Azoic  rocks  (Laurentian). 
Going  at  a  right  angle  with  the  strike,  from  northwTest  to  southeast, 
one  finds  the  following  zones,  which,  however,  can  not  be  sharply  sepa- 
rated. (1)  Silurian:  Crystalline  limestones,  conglomerates,  heavy 
quartzites,  and  slates  (often  gold  bearing),  semimetamorphosed.  (2) 
Huronian:  Mica  slates  and  schists  (with  garnets),  limestones,  coarse- 
grained granites,  diorites,  quartzites,  and  clay  slates  (sometimes  gold 
bearing)  ;  the  mica  schists  often  alternating  with  gneisses;  associated 
with  graphite  and  graphitic  slates,  itacolumite,  specular  ore,  brown 
hematite,  etc.  (3)  Huronian  or  Upper  Laurentian:  Gneisses  (mica- 
ceous and  hornblendic),  granite,  diorite,  mica  schists,  quartzites,  slates 
(sometimes  gold  bearing),  associated  with  chloritic  schists  and  stea- 
tites, mica  with  tourmaline  crystals,  etc.  Some  of  the  granites  have 
the  characteristics  of  eruptive  rocks. 
Smith,104  in  1896,  gives  a  general  account  of  the  character,  distri- 
bution, and  structure  of  the  crystalline  rocks  of  Alabama.  The 
rocks  are  altered  sedimentary  and  igneous  rocks.  The  altered  sedi- 
mentary rocks,  called  the  Talladega  or  Ocoee  series,  are  referred 
to  the  Algonkian,  and  the  altered  igneous  rocks  are  referred  to  the 
Archean. 
The  Talladega  series  is  found  in  the  northeastern  part  of  the  State, 
in  four  or  five  roughly  parallel  belts,  running  northeast-southwest, 
the  strata  in  general  dipping  to  the  southeast.  The  series  comprises, 
in  order  of  abundance,  clay  slates  or  argillites,  in  places  impregnated 
with  graphite,  quartzites  and  quartzite  conglomerates,  and  crystalline 
limestones  or  dolomites.  The  slates,  quartzites,  and  conglomerates 
resemble  veiy  strongly  certain  strata  of  undoubted  Cambrian  age, 
and  it  is  probable  that  some  of  the  strata  included  with  the  Talladega 
are  altered  Cambrian  rocks.  As  yet,  however,  no  fossils  have  been 
discovered  in  them. 
The  altered  igneous  rocks  occur  in  three  main  belts,  roughly  paral- 
lel with  the  sedimentary  belts  in  the  northeastern  part  of  the  State. 
In  order  of  abundance  they  are  gneisses  and  mica  schists,  cut  by 
dikes  of  granite,  diorite,  and  various  hornblendic,  pyroxenic,  and 
chrysolitic  rocks. 
