3MMONS.]         COPPER    IN    RED    BEDS    OF    COLORADO    PLATEAU.  225 
;o  have  been  deposited  contemporaneously  with  the  limestone  in  a 
Silurian  ocean.  On  the  other  hand,  Beck  classes  the  Lake  Superior 
ron  ores  as  sediments,  though  he  accepts  Van  Hise's  explanation  that 
hey  are  concentrations,  metasomatically  replacing  the  sediments  in 
vhich  they  occur. 
The  tendency  to  return  to  the  sedimentary  theory  is  shown  by 
iVeidman  in  his  recent  report  on  the  Baraboo  iron  ores,  where  he 
;laims  that  there  are  no  evidences  of  metasomatic  action,  and  hence 
jssumes  that  these  ores  are  of  sedimentary  origin,  in  expressed  oppo- 
sition to  the  views  of  Van  Hise  and  others.  The  moral  to  be  drawn 
Prom  these  rather  conflicting  statements  seems  to  be  that,  while  we 
should  give  proper  attention  to  the  possibility  that  the  materials  of 
i  deposit  may  have  been  originally  formed  contemporaneously  with 
he  inclosing  sediments,  we  should  not  at  once  assume  a  syngenetic 
>rigin  for  the  deposits  as  they  exist  to-day. 
I  will  now  pass  in  hasty  review  a  few  of  the  known  occurrences  of 
:opper  ores  in  the  Permian  and  Triassic  beds  of  the  West  which  seem 
o  bear  upon  the  question  under  consideration.  They  appear  to  have 
>een  first  noticed  in  northern  New  Mexico  west  of  Santa  Fe,  at  Abiquiu, 
tnd  in  the  Nacimiento  Mountains  by  J.  S.  Newberry  during  the 
Macomb  expedition  of  1859.  They  consist  of  copper  ores,  mainly 
'arbonates,  occurring  in  the  lighter  colored  sandstones  overlying 
he  red  beds  which  contain  plentiful  plant  remains,  frequently  re- 
)laced  by  copper  carbonates,  and  which  Newberry  regarded  as  of 
[riassic  age.  The  same  deposits  were  afterwards  reported  upon  by 
T.  N.  F.  Cazin  (1880)  and  considered  of  economic  value. 
The  flat-lying  red  beds  of  northern  Texas,  along  the  valleys  of  the 
led  and  Brazos  rivers,  have  long  been  known  to  carry  copper,  and 
Lttempts  have  been  made  in  recent  years  to  exploit  them.     They 
lave  recently  been  reported  on  by  E.  J.  Schmitz  (1896),a  who  says 
hey  consist  mainly  of  carbonates  and  silicates,  largely  as  a  replace- 
lent  of  plant  remains,  and  also  impregnating  marls  and  as  pebbles 
n  a  conglomerate.     The  beds  are  considered  by  him  to  be  of  Per- 
ian  age,  and  the  copper  ores  have  been  traced  over  wide  areas 
a  radius  of  more  than  40  miles.     There  are  no  plu tonic  phenomena 
the  region,  and  his  judgment  is  that  the  occurrences  "  give  indis- 
utable   evidence   of   the   origin   of   the   copper   ores   by   precipita- 
.on   during  the   deposition   of   the   copper-bearing   stratum,   or   by 
placement  and  metamorphosis  shortly  after  the  deposition  of  the 
rata.'1     He  finds  a  resemblance  of  these  to  the  Mansfield  deposits, 
lough  they  arc  more  irregularly  distributed,  and  argues  a  similarity 
origin. 
a  Trans.  Am.  Inst.  Min.  Eng.,  vol,  26,  pp.  97-108, 
Bull.  260—05  M 15 
