﻿170 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  Most 
  of 
  the 
  outlets 
  were 
  made 
  before 
  any 
  of 
  the 
  land 
  surveys, 
  

   and 
  we 
  have 
  a 
  record 
  of 
  the 
  formation 
  of 
  one 
  of 
  them 
  only. 
  

   In 
  1 
  841 
  Lieut. 
  Col. 
  Long 
  says: 
  " 
  Commencing 
  at 
  the 
  southern 
  

   boundary 
  of 
  Arkansas 
  and 
  proceeding 
  downwards, 
  we 
  have 
  in 
  

   succession 
  the 
  following 
  considerable 
  outlets 
  from 
  the 
  main 
  

   river, 
  communicating 
  more 
  or 
  less 
  directly 
  with 
  Caddo, 
  or 
  Sodo 
  

   lake, 
  situated 
  on 
  the 
  southwest 
  or 
  right 
  side 
  of 
  the 
  valley, 
  viz.: 
  

   Red 
  bayou, 
  which 
  is 
  the 
  uppermost 
  of 
  all 
  the 
  bayous 
  within 
  the 
  

   district 
  just 
  mentioned; 
  New 
  bayou, 
  Dooly's 
  bayou, 
  and 
  Chef- 
  

   tel's 
  bayou, 
  besides 
  several 
  others 
  of 
  inferior 
  size. 
  The 
  three 
  

   bayous 
  first 
  mentioned 
  are 
  situated 
  above 
  the 
  head 
  of 
  the 
  raft 
  ; 
  

   while 
  the 
  last 
  passes 
  from 
  the 
  river 
  at 
  a 
  point 
  about 
  midway 
  of 
  

   the 
  new 
  or 
  present 
  raft. 
  One 
  of 
  these 
  outlets, 
  viz. 
  : 
  New 
  bayou, 
  

   has 
  been 
  formed 
  during 
  the 
  existence 
  of 
  the 
  present 
  raft."* 
  

  

  Sedimentatioyi 
  . 
  — 
  One 
  of 
  the 
  most 
  important 
  changes 
  wrought 
  by 
  

   the 
  raft 
  was 
  the 
  building 
  up 
  of 
  the 
  land 
  by 
  sedimentation. 
  The 
  

   checking 
  of 
  the 
  current 
  by 
  the 
  raft, 
  the 
  large 
  stretches 
  of 
  almost 
  

   dead 
  water 
  both 
  in 
  the 
  river 
  and 
  the 
  lakes 
  afforded 
  conditions 
  for 
  

   the 
  rapid 
  deposition 
  of 
  sediment 
  that 
  are 
  seldom 
  excelled. 
  

  

  The 
  result 
  was 
  that, 
  in 
  the 
  stream 
  channel 
  over 
  fifteen 
  feet 
  of 
  

   sediment 
  was 
  deposited. 
  Along 
  the 
  banks 
  the 
  deposition 
  ranged 
  

   from 
  a 
  very 
  thin 
  layer 
  on 
  the 
  higher 
  portions 
  to 
  ten 
  or 
  even 
  more 
  

   feet 
  at 
  lower 
  levels. 
  Lieut. 
  Woodruff 
  says 
  in 
  regard 
  to 
  the 
  

   average 
  rate 
  of 
  deposition 
  : 
  "I 
  think 
  that 
  the 
  average 
  increase 
  

   of 
  elevation 
  of 
  the 
  immediate 
  banks 
  of 
  the 
  river 
  and 
  principal 
  

   bayous 
  from 
  near 
  Carolina 
  bluffs 
  to 
  the 
  present 
  head 
  of 
  the 
  raft, 
  

   during 
  the 
  past 
  thirty 
  years, 
  is 
  about 
  3 
  feet. 
  Mr. 
  James 
  Marks, 
  

   an 
  intelligent 
  and 
  observant 
  resident 
  near 
  Carolina 
  bluffs, 
  

   estimates 
  this 
  deposit 
  at 
  five 
  feet."f 
  In 
  the 
  lakes 
  the 
  deposition 
  

   was 
  much 
  more 
  irregular 
  and 
  generally 
  slower. 
  There 
  seems 
  to 
  

   be 
  no 
  way 
  of 
  determining 
  even 
  approximately 
  the 
  deposition 
  in 
  

   the 
  lakes. 
  In 
  the 
  region 
  of 
  the 
  Indian 
  mounds 
  in 
  Sec. 
  5, 
  19 
  N., 
  

   14 
  W., 
  which 
  was 
  all 
  under 
  water 
  during 
  the 
  raft 
  period, 
  there 
  

   is 
  a 
  layer 
  of 
  stiff 
  red 
  clay 
  from 
  6 
  inches 
  to 
  a 
  foot 
  thick 
  overlying 
  

   a 
  black 
  sandy 
  clay 
  similar 
  to 
  that 
  on 
  the 
  Caddo 
  prairie. 
  

  

  *27th 
  Cong. 
  1st 
  Sess. 
  Senate 
  Doc, 
  vol 
  i, 
  No. 
  64, 
  pp. 
  3-4. 
  

  

  ■f-43d 
  Cong; 
  ist 
  Sess. 
  House 
  Ex. 
  Doc. 
  vol. 
  2 
  part 
  2, 
  p. 
  642, 
  1873. 
  

  

  