﻿ii6 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  Swallow 
  in 
  1855.* 
  This 
  term 
  has 
  since 
  been 
  used 
  bj'^ 
  a 
  number 
  

   of 
  southern 
  geologists 
  but 
  with 
  varying 
  shades 
  of 
  meaning. 
  

   Hilgard 
  used 
  the 
  term 
  as 
  a 
  S5monym 
  for 
  the 
  loess 
  proper. 
  In 
  his 
  

   second 
  annual 
  report 
  Hopkins 
  used 
  the 
  term 
  ' 
  ' 
  Bluff 
  Period 
  ' 
  ' 
  to 
  

   cover 
  the 
  whole 
  of 
  the 
  Quaternary 
  except 
  the 
  most 
  modern 
  

   alluvium. 
  

  

  General 
  characteristics 
  of 
  the 
  loess. 
  — 
  The 
  loess 
  is 
  a 
  homogeneous, 
  

   yellow 
  or 
  yellowish-buff, 
  vfery 
  fine 
  grained, 
  calcareous, 
  silty, 
  

   unstratified 
  loam 
  ; 
  commonly 
  best 
  developed 
  along 
  the 
  hills 
  bor- 
  

   dering 
  the 
  river 
  channels, 
  and 
  thinning 
  out 
  and 
  becoming 
  less 
  

   characteristic 
  as 
  the 
  distance 
  from 
  the 
  stream 
  channels 
  increases. 
  

   It 
  often 
  contains 
  numerous 
  land 
  shells 
  and 
  occasionally 
  fresh 
  

   water 
  shells. 
  In 
  its 
  basal 
  portions 
  mastodon 
  bones 
  have 
  been 
  

   found 
  and 
  L,yell 
  reports 
  the 
  finding 
  of 
  fish 
  remains 
  in 
  the 
  loess 
  

   at 
  Vicksburg.f 
  The 
  calcareous 
  matter 
  forms 
  very 
  fantastically 
  

   shaped 
  concretions 
  called 
  loess-kindchen. 
  Probably 
  the 
  most 
  

   distinctive 
  feature 
  of 
  the 
  loess 
  is 
  its 
  habit 
  of 
  weathering 
  into 
  

   perpendicular 
  banks. 
  

  

  In 
  the 
  Mississippi 
  valley 
  it 
  seems 
  to 
  be 
  best 
  developed 
  along 
  

   the 
  eastern 
  bluffs 
  and 
  to 
  grade 
  southward 
  into 
  a 
  5'ellow 
  loam 
  or 
  

   hardpan. 
  Typical 
  loessr 
  is 
  probably 
  to 
  be 
  found 
  in 
  Louisiana 
  

   only 
  over 
  a 
  voxy 
  limited 
  area 
  in 
  the 
  Florida 
  parishes 
  along 
  the 
  

   river 
  immediately 
  south 
  of 
  the 
  Mississippi 
  line 
  and 
  at 
  Sicily 
  

   island. 
  The 
  loess, 
  in 
  its 
  modified 
  form, 
  the 
  yellow 
  loam, 
  how- 
  

   ever, 
  covers 
  a 
  very 
  considerable 
  area 
  in 
  the 
  State. 
  

  

  Origin 
  of 
  the 
  loess. 
  — 
  No 
  satisfactory 
  theory 
  of 
  the 
  origin 
  of 
  

   the 
  loess 
  has 
  yet 
  been 
  advanced. 
  Geologists 
  are 
  at 
  present 
  

   divided 
  between 
  two 
  theories, 
  the 
  aqueous 
  and 
  the 
  eolian. 
  There 
  

   are 
  several 
  modifications 
  of 
  the 
  aqueous 
  : 
  the 
  strictly 
  fluviatile, 
  

   the 
  fiuvio-lacustrine, 
  the 
  true 
  lacustrine 
  and 
  the 
  embayment.J 
  

   All 
  geologists 
  agree 
  that 
  the 
  loess 
  and 
  the 
  yellow 
  loam 
  are 
  formed 
  

   of 
  glacial 
  products. 
  

  

  The 
  Yellow 
  loam. 
  — 
  The 
  studies 
  of 
  Hilgard 
  in 
  Mississippi, 
  prior 
  

   to 
  i860, 
  indicated 
  the 
  presence 
  of 
  a 
  stratum 
  of 
  unstratified, 
  non- 
  

  

  * 
  Geol. 
  Surv. 
  of 
  Missouri, 
  istand 
  2d 
  Annual 
  Report, 
  pp. 
  59-170, 
  Jefferson 
  

   City, 
  1855. 
  

   f 
  Principles 
  of 
  Geology, 
  irth 
  ed. 
  , 
  vol. 
  i, 
  p. 
  460. 
  

   X 
  Chamberlin, 
  Jour. 
  Geol., 
  vol. 
  5, 
  1897, 
  p. 
  798, 
  

  

  