﻿i88 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  subsidence 
  is 
  going 
  on 
  it 
  does 
  not 
  seem 
  probable 
  that 
  the 
  line 
  of 
  

   maximum 
  depression 
  should 
  follow 
  the 
  Red 
  river 
  valley, 
  and 
  if 
  

   it 
  extends 
  over 
  a 
  large 
  area 
  all 
  the 
  streams 
  of 
  that 
  area 
  should 
  be 
  

   affected 
  alike. 
  That 
  is, 
  we 
  would 
  look 
  for 
  lakes 
  of 
  the 
  same 
  type 
  

   along 
  the 
  valleys 
  of 
  the 
  Brazos, 
  the 
  Trinity, 
  the 
  Sabine 
  and 
  the 
  

   Ouachita 
  and 
  especially 
  along 
  the 
  Arkansas, 
  which 
  in 
  point 
  of 
  

   size 
  and 
  amount 
  of 
  sediment 
  it 
  carries, 
  fully 
  equals 
  the 
  Red. 
  

   Lakes 
  should 
  also 
  be 
  found 
  in 
  Red 
  river 
  valley 
  above 
  the 
  region 
  

   effected 
  by 
  the 
  raft. 
  No 
  lakes 
  like 
  Ferr}'-, 
  Cross 
  or 
  Bistineau 
  

   lakes 
  are 
  found. 
  

  

  This 
  seems 
  to 
  leave 
  only 
  the 
  theory 
  of 
  the 
  raft 
  formation 
  of 
  

   these 
  lakes. 
  This 
  theory 
  is 
  greatly 
  strengthened 
  by 
  the 
  known 
  

   formation 
  of 
  a 
  large 
  lake 
  similar 
  to 
  Sodo 
  lake 
  just 
  below 
  Miller's 
  

   bluffs 
  by 
  the 
  closing 
  of 
  the 
  outlet 
  bayou 
  by 
  the 
  raft. 
  Then 
  there 
  

   is 
  the 
  simi-historical 
  account 
  of 
  the 
  formation 
  of 
  Sodo 
  lake 
  proven 
  

   as 
  it 
  is 
  by 
  the 
  old 
  tree 
  stumps 
  and 
  the 
  Indian 
  mounds. 
  This 
  

   theory, 
  however, 
  requires 
  that 
  the 
  lakes 
  be 
  drained 
  on 
  the 
  

   removal 
  of 
  the 
  raft. 
  This 
  has 
  not 
  been 
  full}" 
  accomplished, 
  

   although 
  a 
  large 
  part 
  of 
  the 
  lake 
  area 
  has 
  been 
  drained. 
  There 
  

   are 
  several 
  possible 
  reasons 
  why 
  the 
  drainage 
  has 
  not 
  been 
  com- 
  

   pleted 
  at 
  the 
  present 
  time 
  : 
  (i) 
  the 
  river 
  may 
  not 
  as 
  yet 
  have 
  

   succeeded 
  in 
  cutting 
  out 
  all 
  the 
  material 
  deposited 
  in 
  the 
  channel 
  

   during 
  the 
  raft 
  period, 
  (2) 
  many 
  of 
  the 
  streams 
  have 
  been 
  super- 
  

   imposed 
  on 
  older 
  clays 
  by 
  the 
  filling 
  of 
  their 
  old 
  channels 
  and. 
  

   have 
  not 
  yet 
  had 
  time 
  to 
  cut 
  new 
  channels 
  to 
  as 
  low 
  a 
  level 
  as 
  the 
  

   old 
  channels. 
  

  

  If, 
  as 
  now 
  seems 
  probable, 
  the 
  lakes 
  owe 
  their 
  formation 
  to 
  

   the 
  raft, 
  it 
  is 
  possible 
  to 
  approximate 
  the 
  date 
  of 
  the 
  forma- 
  

   tion 
  of 
  Cross 
  and 
  Ferry 
  lakes. 
  The 
  distance, 
  counting 
  the 
  old 
  

   stream 
  detours, 
  from 
  Cross 
  lake 
  outlet 
  to 
  the 
  head 
  of 
  the 
  Shreve 
  

   raft 
  in 
  1838, 
  is 
  49 
  miles. 
  If 
  four-fifths 
  of 
  a 
  mile 
  represents 
  the 
  

   normal 
  rate 
  of 
  advance 
  of 
  the 
  raft, 
  about 
  61 
  years 
  had 
  elapsed 
  in 
  

   1838, 
  since 
  the 
  closing 
  of 
  Cross 
  lake 
  bayou 
  by 
  the 
  raft. 
  This 
  

   would 
  make 
  the 
  date 
  of 
  the 
  formation 
  of 
  these 
  lakes 
  about 
  1777. 
  

  

  