﻿I'lie 
  Karoo 
  System 
  in 
  Northern 
  Rhodesia. 
  439 
  

  

  2. 
  'On 
  the 
  Karroo 
  System 
  in 
  Northern 
  Rhodesia, 
  and 
  its 
  

   relation 
  to 
  the 
  General 
  Geology.' 
  By 
  Arthur 
  John 
  Charles 
  

   Molyneux, 
  F.G.S. 
  

  

  In 
  1903 
  (Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  lix.) 
  the 
  author 
  described 
  

   the 
  occurrence 
  of 
  deposits, 
  that 
  have 
  since 
  been 
  recognized 
  as 
  of 
  

   Karroo 
  age, 
  in 
  Southern 
  Rhodesia. 
  The 
  present 
  communication 
  

   traces 
  their 
  extension 
  across 
  the 
  Zambesi, 
  where 
  their 
  boundary 
  

   follows 
  the 
  foot 
  of 
  the 
  remarkable 
  line 
  of 
  escarpments 
  that 
  divide 
  

   the 
  plateau, 
  nearly 
  4000 
  feet 
  in 
  altitude, 
  from 
  the 
  low-lying 
  

   (1500 
  feet) 
  regions 
  of 
  the 
  Zambesi 
  Valley. 
  Karroo 
  deposits 
  also 
  

   form 
  the 
  floor 
  of 
  the 
  peculiar 
  trench-like 
  valleys 
  of 
  the 
  Luangwa, 
  

   Lukasashi, 
  and 
  Lusenfwa 
  (or 
  Luano), 
  the 
  walls 
  of 
  which 
  are 
  

   similarly 
  steep, 
  and 
  of 
  metamorphic 
  rock-gneiss, 
  schist, 
  and 
  

   granite. 
  

  

  The 
  Luano 
  Valley 
  is 
  described. 
  Its 
  northern 
  precipice 
  is 
  known 
  

   as 
  the 
  Machinga 
  (native 
  meaning 
  ' 
  a 
  fence 
  '), 
  and 
  the 
  Lusenfwa 
  

   and 
  Molongushi 
  rivers 
  are 
  followed 
  in 
  their 
  mature 
  courses 
  across 
  

   the 
  flat 
  plateau-plains. 
  They 
  reach 
  the 
  Luano 
  by 
  waterfalls 
  into 
  

   deeply 
  incised 
  gorges, 
  cutting 
  back 
  15 
  and 
  8 
  miles 
  respectively 
  

   into 
  the 
  plateau. 
  Rivers 
  that 
  join 
  the 
  Luano 
  from 
  the 
  south, 
  on 
  

   the 
  contrary, 
  descend 
  into 
  open 
  valleys 
  of 
  Karroo 
  floors, 
  that 
  are 
  

   divided 
  one 
  from 
  the 
  other 
  by 
  tongues 
  from 
  the 
  southern 
  highlands, 
  

   and 
  suggest 
  ' 
  rolled-out 
  ' 
  folds. 
  

  

  Between 
  the 
  Kafue 
  junction 
  and 
  Peira, 
  the 
  Zambesi 
  River 
  also 
  

   occupies 
  a 
  trough-valley, 
  lined 
  by 
  steep 
  escarpments; 
  that 
  on 
  the 
  

   south 
  side 
  rises 
  2000 
  feet 
  in 
  less 
  than 
  a 
  mile, 
  being 
  formed 
  of 
  a 
  

   flexure 
  of 
  altered 
  sediments. 
  The 
  Danda 
  flats 
  show 
  Karroo 
  beds. 
  

  

  The 
  Lufua 
  River 
  runs 
  parallel 
  with 
  the 
  strike 
  of 
  the 
  gneiss 
  of 
  

   the 
  locality, 
  and 
  crosses 
  two 
  synclinal 
  basins 
  of 
  clastic 
  deposits, 
  

   separated 
  by 
  Archaean 
  ridges. 
  The 
  Losito 
  has 
  also 
  a 
  deep 
  strike- 
  

   channel. 
  

  

  The 
  Karroo 
  deposits 
  are 
  grouped 
  into 
  basal 
  conglomerates, 
  coal- 
  

   measures, 
  Upper 
  Matobola 
  Beds, 
  and 
  Escarpment 
  Series. 
  No 
  

   effiisive 
  basalts 
  were 
  seen, 
  but 
  there 
  is 
  an 
  area 
  of 
  Forest 
  Sand- 
  

   stones 
  near 
  the 
  Losito-Zambesi 
  confluence. 
  In 
  the 
  Luano 
  Valley, 
  

   the 
  conglomerates 
  are 
  made 
  up 
  of 
  resisting 
  quartz 
  - 
  quartzite 
  

   boulders 
  and 
  ])ebbles 
  — 
  all 
  ha^^ing 
  dimpled 
  or 
  concave 
  depressions 
  

   on 
  one 
  or 
  more 
  sides 
  ; 
  they 
  possess 
  no 
  orientation, 
  are 
  unsorted, 
  and 
  

   exhibit 
  a 
  varying 
  matrix. 
  Though 
  they 
  form 
  the 
  base 
  of 
  the 
  Karroo 
  

   System 
  there 
  is 
  no 
  certain 
  evidence 
  of 
  glaciation, 
  but 
  the 
  beds 
  seem 
  

   to 
  have 
  originated 
  as 
  scree-deposits 
  on 
  an 
  uneven 
  floor. 
  The 
  

   grinding 
  of 
  the 
  pebbles 
  into 
  one 
  another 
  is 
  accounted 
  for 
  by 
  the 
  

   soft 
  nature 
  of 
  the 
  schists 
  and 
  limestones, 
  which 
  would 
  have 
  been 
  

   removed 
  in 
  the 
  internal 
  movement 
  before 
  consolidation. 
  

  

  In 
  the 
  Lukasashi 
  and 
  the 
  Luano 
  there 
  is 
  a 
  general 
  dip 
  of 
  the 
  

   strata 
  north-westwards, 
  that 
  is, 
  towards 
  the 
  escarpment, 
  and 
  

   evidence 
  of 
  minor 
  anticlinal 
  and 
  synclinal 
  folds 
  along 
  east-north- 
  

   east 
  axes. 
  By 
  a 
  combination 
  of 
  these 
  the 
  Karroo 
  deposits 
  become 
  

  

  