﻿440 
  Geological 
  Society. 
  

  

  lowered 
  from 
  plateau-level 
  on 
  the 
  south, 
  towards 
  the 
  north-west 
  

   culminating 
  in 
  a 
  great 
  downthrow 
  fault 
  along 
  the 
  foot 
  of 
  the 
  

   Machinga. 
  

  

  Nowhere 
  on 
  the 
  plateau 
  in 
  the 
  immediate 
  vicinity 
  of 
  the 
  valley- 
  

   walls 
  have 
  Karroo 
  beds 
  been 
  found, 
  and 
  if 
  they 
  did 
  once 
  extend 
  

   there, 
  it 
  is 
  remarkable 
  that 
  they 
  should 
  have 
  disappeared. 
  But 
  it 
  

   is 
  certain 
  that 
  the 
  valleys 
  were 
  at 
  one 
  time 
  filled 
  almost 
  to 
  plateau- 
  

   level, 
  as 
  the 
  rivers 
  pass 
  through 
  Archaean 
  inliers 
  by 
  deep 
  clefts, 
  and 
  

   must 
  thus 
  have 
  laid 
  out 
  their 
  courses 
  before 
  such 
  hard 
  masses 
  rose 
  

   from 
  the 
  Karroo 
  beds 
  by 
  erosion 
  of 
  the 
  latter. 
  Also 
  the 
  compara- 
  

   tively 
  late 
  times 
  in 
  which 
  the 
  Machinga 
  escarpment 
  was 
  laid 
  bare, 
  

   and 
  the 
  rejuvenation 
  of 
  the 
  Lusenfwa 
  Eiver, 
  etc., 
  suggest 
  a 
  complete 
  

   fiUing 
  of 
  the 
  valleys. 
  

  

  It 
  is 
  thus 
  possible 
  that 
  the 
  Karroo 
  beds 
  extended 
  over 
  a 
  part 
  

   of 
  the 
  plateau, 
  and 
  were 
  included 
  in 
  the 
  folding 
  and 
  faulting 
  

   movements 
  already 
  mentioned. 
  Subsequently, 
  by 
  some 
  continuous 
  

   agency 
  the 
  whole 
  surface 
  was 
  planed 
  off 
  to 
  a 
  plateau 
  of 
  remarkable 
  

   monotony 
  ; 
  and 
  on 
  a 
  further 
  radical 
  change 
  of 
  conditions 
  taking 
  

   place, 
  erosion 
  of 
  the 
  softer 
  Karroo 
  strata 
  set 
  in 
  by 
  which 
  the 
  

   present 
  valleys 
  are 
  again 
  reaching 
  a 
  plane 
  of 
  denudation. 
  

  

  The 
  facility 
  with 
  which 
  atmospheric 
  waters 
  and 
  acids 
  attack 
  the 
  

   sediments 
  is 
  notable, 
  and 
  decomposition 
  extends 
  to 
  100 
  feet 
  in 
  

   depth 
  over 
  the 
  flat 
  regions 
  of 
  the 
  plains. 
  

  

  The 
  author 
  suggests 
  that 
  the 
  trough-valleys 
  of 
  clastic 
  rocks 
  merely 
  

   follow 
  the 
  axis 
  of 
  pre-Karroo 
  and 
  post-Karroo 
  movements 
  — 
  trending^ 
  

   in 
  three 
  directions. 
  The 
  Luano 
  and 
  part 
  of 
  the 
  Zambesi 
  course 
  

   agree 
  with 
  that 
  of 
  the 
  folds 
  and 
  cleavage 
  of 
  the 
  complex, 
  certain 
  

   ranges 
  of 
  hills, 
  and 
  the 
  Machinga 
  Fault 
  (east-north-east) 
  ; 
  a 
  second 
  

   (south-easterly) 
  trend 
  is 
  that 
  of 
  the 
  Kafue, 
  Losito, 
  Inyanga 
  range, 
  and 
  

   Lufua, 
  and 
  the 
  folds 
  and 
  cleavage 
  of 
  the 
  complex 
  in 
  these 
  regions 
  ; 
  

   while 
  the 
  third 
  follows 
  the 
  dominant 
  direction 
  of 
  the 
  great 
  tectonic 
  

   movements 
  of 
  South 
  Africa 
  (north-east). 
  Mr. 
  L. 
  A. 
  Wallace 
  has 
  

   noted 
  that 
  the 
  Luangwa 
  and 
  mid-Zambesi 
  are 
  on 
  this 
  strike, 
  and 
  

   Mr. 
  G. 
  W. 
  Lamplugh 
  has 
  suggested 
  a 
  northerly 
  extension 
  of 
  his 
  Deka 
  

   Fault. 
  A 
  distance 
  of 
  800 
  miles 
  thus 
  displays 
  movements 
  that 
  

   commenced 
  in 
  pre-Karroo 
  periods, 
  and 
  have 
  repeated 
  themselves 
  

   since 
  the 
  Karroo 
  time. 
  

  

  Fossils 
  from 
  the 
  areas 
  described 
  support 
  the 
  previous 
  allocation 
  

   of 
  the 
  deposits 
  to 
  the 
  Permo-Carboniferous, 
  and 
  to 
  the 
  Karroo 
  

   System 
  of 
  South 
  Africa. 
  Notable 
  specimens 
  are 
  members 
  of 
  the 
  

   Glossopteris-^oidi^ 
  including 
  pith-casts 
  of 
  Schizoneura 
  ; 
  carapaces 
  of 
  

   Estheria 
  ; 
  ostracods 
  ; 
  and 
  fragments 
  of 
  bone, 
  fish-scales, 
  and 
  teeth. 
  

  

  Palaeolithic 
  stone-implements 
  (axe-heads) 
  were 
  found 
  at 
  separate 
  

   localities 
  on 
  the 
  surface, 
  about 
  the 
  latitude 
  of 
  14° 
  50' 
  S. 
  

  

  