﻿W. 
  TOPLEY 
  ON 
  AREAS 
  OF 
  APPARENT 
  UPHEAVAL. 
  187 
  

  

  2. 
  The 
  Jurassic 
  and 
  Triassic 
  Rocks 
  of 
  Central 
  England*. 
  — 
  As 
  an 
  

   illustration 
  of 
  the 
  thinning 
  out 
  of 
  the 
  Oolitic 
  rocks 
  of 
  this 
  area, 
  we 
  

   may 
  take 
  a 
  section 
  from 
  Leckhampton 
  to 
  Burford 
  (fig. 
  1). 
  

  

  Leckhampton 
  Hill 
  is 
  one 
  of 
  the 
  prominent 
  points 
  of 
  the 
  Cotteswold 
  

   escarpment 
  ; 
  and 
  here 
  the 
  thickness 
  of 
  the 
  Inferior 
  Oolite 
  has 
  been 
  

   carefully 
  measured. 
  If 
  the 
  summit 
  of 
  this 
  hill 
  were 
  capped 
  by 
  Great 
  

   Oolite, 
  the 
  base 
  of 
  that 
  formation 
  would 
  be 
  at 
  an 
  elevation 
  of 
  nearly 
  

   1000 
  feet. 
  At 
  Burford, 
  which 
  lies 
  19 
  miles 
  a 
  little 
  to 
  the 
  south 
  of 
  

   east 
  of 
  Leckhampton 
  Hill, 
  the 
  average 
  elevation 
  of 
  the 
  base 
  of 
  the 
  

   Great 
  Oolite 
  is 
  about 
  400 
  feet. 
  In 
  ordinary 
  geological 
  language 
  we 
  

   should 
  then 
  say, 
  that 
  from 
  Leckhampton 
  Hill 
  to 
  Burford 
  the 
  beds 
  

   have 
  a 
  dip 
  of 
  600 
  feet 
  in 
  19 
  miles. 
  

  

  Along 
  this 
  line 
  the 
  exact 
  amount 
  of 
  the 
  thinning 
  of 
  the 
  Inferior 
  

   Oolite 
  and 
  Upper 
  and 
  Middle 
  Lias 
  is 
  well 
  known, 
  and 
  that 
  of 
  the 
  

   Lower 
  Lias 
  may 
  be 
  approximately 
  inferred. 
  At 
  Leckhampton 
  the 
  

   thickness 
  of 
  strata 
  intervening 
  between 
  the 
  base 
  of 
  the 
  Great 
  Oolite 
  

   and 
  the 
  base 
  of 
  the 
  Lias 
  is 
  about 
  1200 
  feet 
  ; 
  at 
  Burford 
  the 
  total 
  

   thickness 
  is 
  probably 
  under 
  200 
  feet. 
  There 
  is 
  therefore 
  a 
  differ- 
  

   ence 
  in 
  thickness 
  between 
  the 
  two 
  places 
  of 
  about 
  1000 
  feet 
  of 
  

   Lower 
  Jurassic 
  strata, 
  whilst 
  the 
  dip 
  of 
  the 
  Great 
  Oolite 
  is 
  only 
  

   600 
  feet 
  in 
  the 
  same 
  distance. 
  Therefore 
  the 
  thinning 
  out 
  of 
  the 
  

   lower 
  beds 
  will 
  far 
  more 
  than 
  account 
  for 
  the 
  observed 
  dip 
  of 
  the 
  

   higher 
  beds. 
  

  

  To 
  make 
  the 
  matter 
  more 
  plain, 
  let 
  us 
  refer 
  both 
  geological 
  

   horizons 
  under 
  consideration 
  to 
  the 
  present 
  sea-level. 
  The 
  base 
  of 
  

   the 
  Great 
  Oolite 
  at 
  Leckhampton 
  would 
  be 
  1000 
  feet 
  above 
  the 
  sea- 
  

   level; 
  at 
  Burford 
  (19 
  miles 
  distant) 
  it 
  is 
  400 
  feet 
  above 
  the 
  sea 
  ; 
  

   therefore 
  the 
  dip 
  of 
  the 
  Great 
  Oolite 
  is 
  from 
  west 
  to 
  east, 
  600 
  feet 
  

   in 
  19 
  miles. 
  The 
  base 
  of 
  the 
  Lias 
  at 
  Leckhampton 
  is 
  about 
  200 
  

   feet 
  below 
  the 
  eea-level, 
  at 
  Burford 
  it 
  is 
  about 
  200 
  feet 
  above 
  it 
  ; 
  

   therefore 
  the 
  dip 
  of 
  the 
  base 
  of 
  the 
  Lias 
  is 
  from 
  east 
  to 
  west, 
  400 
  

   feet 
  in 
  the 
  same 
  distance 
  of 
  19 
  miles. 
  

  

  But 
  we 
  have 
  here 
  only 
  considered 
  the 
  thinning 
  of 
  the 
  Inferior 
  

   Oolite 
  and 
  Lias, 
  whereas 
  it 
  is 
  known 
  that 
  the 
  New 
  Bed 
  series 
  thins 
  

   in 
  like 
  manner 
  in 
  the 
  same 
  direction. 
  The 
  amount 
  of 
  this 
  thinning 
  

   cannot 
  be 
  even 
  approximately 
  known 
  between 
  these 
  two 
  places 
  ; 
  but 
  

   it 
  wiU 
  probably 
  be 
  several 
  hundred 
  feet. 
  

  

  The 
  thickness 
  of 
  the 
  Trias 
  in 
  Cheshire 
  is 
  given 
  by 
  Professor 
  Hull 
  

   as 
  5600 
  feet, 
  and 
  about 
  600 
  feet 
  in 
  East 
  Warwickshire 
  ; 
  it 
  is 
  pro- 
  

   bably 
  absent 
  under 
  Oxford. 
  From 
  Cheshire 
  to 
  Warwickshire 
  the 
  

   Trias 
  thins 
  5000 
  feet 
  in 
  about 
  80 
  miles, 
  or 
  about 
  62 
  feet 
  per 
  mile. 
  

   If 
  this 
  district 
  were 
  covered 
  by 
  higher 
  Secondary 
  rocks, 
  the 
  dip 
  of 
  

  

  * 
  The 
  data 
  for 
  the 
  observations 
  are 
  taken 
  from 
  Prof. 
  Hull's 
  paper 
  already 
  re- 
  

   ferred 
  to, 
  and 
  from 
  the 
  same 
  author's 
  Geological-Survey 
  Memoir, 
  on 
  Sheet 
  44. 
  

   [It 
  was 
  pointed 
  out 
  by 
  Mr. 
  Bauerman 
  and 
  Mr. 
  Etheridge, 
  during 
  the 
  discussion 
  

   upon 
  this 
  paper, 
  that 
  borings 
  near 
  Burford 
  have 
  proved 
  the 
  thinning 
  of 
  the 
  Lower 
  

   Lias 
  to 
  be 
  less 
  rapid 
  than 
  had 
  formerly 
  been 
  supposed. 
  Therefore 
  the 
  westerly 
  

   dip 
  of 
  the 
  base 
  of 
  the 
  Lias 
  would 
  be 
  less 
  than 
  that 
  shown 
  in 
  the 
  figure. 
  The 
  chief 
  

   point 
  of 
  my 
  argument, 
  however, 
  still 
  remains, 
  that 
  the 
  easterly 
  dip 
  of 
  the 
  Great 
  

   Oolite 
  can 
  be 
  entirely 
  accounted 
  for 
  by 
  the 
  thinning 
  of 
  the 
  Inferior 
  Oolite 
  and 
  

   Upper 
  and 
  Middle 
  Lias.] 
  

  

  