﻿ROCKS 
  OF 
  THE 
  LEICESTERSHIRE 
  COAL-EIELD. 
  27 
  

  

  is 
  distinctly 
  recognizable 
  as 
  partially 
  decomposed 
  diorite, 
  similar 
  to 
  

   the 
  diorites 
  intrusive 
  in 
  the 
  Upper 
  Cambrian 
  (Stockingford) 
  Shales 
  

   of 
  the 
  Nuneaton 
  district. 
  

  

  Carboniferous 
  Bocks. 
  — 
  Fragments 
  referable 
  to 
  the 
  Carboniferous 
  

   rocks 
  of 
  the 
  neighbourhood 
  are, 
  in 
  the 
  breccias 
  of 
  some 
  localities, 
  

   very 
  plentiful, 
  whilst 
  in 
  others 
  they 
  are 
  remarkably 
  scarce, 
  thus 
  

   forming 
  a 
  marked 
  contrast 
  to 
  the 
  more 
  regular 
  distribution 
  of 
  the 
  

   felspathic 
  grits 
  which 
  have 
  been 
  brought 
  from 
  further 
  afield. 
  This 
  

   is 
  well 
  shown 
  in 
  the 
  table 
  on 
  p. 
  24. 
  As 
  a 
  rule, 
  these 
  fragments 
  

   have 
  been 
  derived 
  from 
  the 
  Coal-measures 
  of 
  the 
  immediate 
  locality, 
  

   and 
  consist 
  of 
  angular 
  pieces 
  of 
  grit, 
  nodules 
  of 
  clay-ironstone, 
  and 
  

   concretions 
  of 
  more 
  or 
  less 
  impure 
  haematite. 
  Within 
  the 
  limits 
  of 
  

   the 
  Leicestershire 
  Coal-field 
  fragments 
  of 
  Mountain 
  Limestone 
  are 
  

   of 
  rare 
  occurrence 
  in 
  the 
  Permian 
  breccias. 
  One 
  such 
  fragment, 
  

   which 
  was 
  very 
  fossiliferous, 
  I 
  have 
  found 
  at 
  Measham, 
  and 
  at 
  the 
  

   Boothorpe 
  Works 
  (Series 
  1) 
  I 
  have 
  found 
  several 
  pieces 
  of 
  impure 
  

   limestone, 
  resembling 
  some 
  of 
  the 
  marginal 
  deposits 
  of 
  Carboniferous 
  

   Limestone 
  at 
  the 
  northern 
  extremity 
  of 
  Charnwood 
  Forest. 
  

  

  At 
  Polesworth, 
  at 
  the 
  northern 
  extremity 
  of 
  the 
  Warwickshire 
  

   Coal-field, 
  nearly 
  10 
  per 
  cent, 
  of 
  the 
  fragments 
  contained 
  in 
  the 
  

   breccias 
  consist 
  of 
  well-rolled 
  pebbles 
  of 
  compact 
  crystalline 
  Carbon- 
  

   iferous 
  Limestone 
  *. 
  

  

  (4) 
  The 
  Origin 
  op 
  the 
  Rock-fragments 
  oe 
  the 
  Breccias. 
  

  

  In 
  attempting 
  to 
  trace 
  the 
  source 
  from 
  which 
  the 
  material 
  now 
  

   forming 
  the 
  Permian 
  beds 
  of 
  the 
  Ashby 
  Coal-field 
  has 
  been 
  derived, 
  

   it 
  is 
  manifest 
  that 
  but 
  little 
  aid 
  can 
  be 
  expected 
  from 
  the 
  brecciated 
  

   fragments 
  derived 
  from 
  the 
  Carboniferous 
  rocks, 
  since, 
  as 
  we 
  have 
  

   already 
  observed, 
  these 
  grits, 
  haematite-nodules, 
  and 
  sparsely 
  scattered 
  

   limestone-fragments 
  have 
  been 
  derived 
  for 
  the 
  most 
  part 
  from 
  the 
  

   denudation 
  of 
  rocks 
  in 
  the 
  immediate 
  neighbourhood, 
  and 
  vary 
  much 
  

   within 
  small 
  distances. 
  For 
  a 
  solution 
  of 
  the 
  problem 
  we 
  must 
  

   question 
  those 
  fragments 
  which 
  so 
  largely 
  predominate 
  in 
  the 
  

   breecias 
  throughout 
  the 
  whole 
  Coal-field, 
  the 
  felspathic 
  grits 
  and 
  

   quartzites, 
  and 
  their 
  associated 
  igneous 
  rocks. 
  

  

  Except 
  in 
  the 
  W'rekin 
  there 
  are 
  no 
  rocks 
  to 
  the 
  north 
  and 
  north- 
  

   east 
  nearer 
  than 
  Scotland 
  which 
  could 
  afford 
  specimens 
  having 
  

   the 
  general 
  characters 
  of 
  these 
  older 
  brecciated 
  fragments. 
  It 
  is 
  

   true 
  that 
  we 
  occasionally 
  find 
  a 
  few 
  which 
  can 
  with 
  a 
  tolerable 
  

   amount 
  of 
  certainty 
  be 
  referred 
  to 
  the 
  Charnwood 
  series 
  ; 
  but 
  except 
  

   in 
  one 
  locality, 
  that 
  of 
  the 
  Hartshorn 
  Brook, 
  these 
  are 
  very 
  rare, 
  and 
  

   form 
  a 
  very 
  small 
  percentage 
  of 
  the 
  total 
  number 
  of 
  fragments. 
  If 
  

  

  * 
  In 
  the 
  face 
  of 
  the 
  above 
  facts 
  I 
  think 
  we 
  cannot 
  refer 
  the 
  source 
  of 
  these 
  

   Polesworth 
  limestone 
  fragments 
  to 
  the 
  bosses 
  of 
  Carboniferous 
  Limestone 
  which 
  

   are 
  exposed 
  on 
  the 
  east 
  side 
  of 
  the 
  Ashby 
  Coal-field 
  ; 
  for 
  were 
  this 
  the 
  case 
  we 
  

   ought 
  to 
  find 
  considerably 
  more 
  of 
  these 
  limestone 
  pebbles 
  than 
  we 
  do 
  in 
  the 
  

   breccias 
  of 
  the 
  country 
  intermediate 
  between 
  these 
  spots. 
  It 
  is 
  far 
  more 
  probable 
  

   that 
  the 
  limestone 
  of 
  the 
  Polesworth 
  breccias 
  was 
  derived 
  from 
  a 
  mass 
  of 
  Car- 
  

   boniferous 
  Limestone 
  lying 
  between 
  the 
  northern 
  extremities 
  of 
  the 
  Warwick- 
  

   shire 
  and 
  South-Staffordshire 
  Coal-fields, 
  but 
  now 
  covered 
  by 
  Triassic 
  strata 
  ; 
  

   or 
  from 
  a 
  hidden 
  boss 
  of 
  limestone 
  still 
  further 
  to 
  the 
  south. 
  

  

  