Nol.  49.]  AN  INTRUSIVE  SHEET  OE  DIABASE  AT  ROBIN  HOOD. 
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39.  Notes  on  an  Intrusive  Sheet  0/ Diabase  and  Associated  Docks 
at  Robin  Hood,  near  Bassenthwaite.  By  J.  Postlethwaite, 
Esq.,  F.G.S.  (Read  june  21st,  1893.) 
This  sheet  of  igneous  rock  extends  in  an  E.N.E.-and-W.S.W. 
direction  from  Bassenfells,  across  Bassenthwaite  Common,  to  a 
point  about  |  mile  S.E.  of  Over  Water,  the  total  distance  being 
about  2|  miles.  The  sheet  varies  considerably  in  thickness,  and  is 
much  broken  up  and  shifted  by  faults ;  generally  the  thickness  is 
from  8  to  12  feet,  but  near  the  western  end,  where  the  diabase  is 
exposed  on  lower  ground,  it  measures  from  80  to  100  feet  in  thick¬ 
ness.  This  portion  of  the  intrusive  sheet,  which  is  about  |  of  a 
mile  in  length,  is  divided  into  two  sections  by  a  fault,  the  western 
section  being  nearly  double  the  length  of  the  eastern  section ;  the 
latter  has  been  shifted  about  100  feet  to  the  north  by  a  fault.  Two 
quarries  have  been  opened  in  the  western  section  for  building-stone 
and  road-metal.  The  next  or  third  exposure,  which  is  a  little  over 
half-a-mile  in  length,  has  been  shifted  still  farther,  namely,  about 
350  yards  to  the  north,  and  the  diabase  is  contracted  to  a  thickness 
of  10  or  12  feet.  Eastward  of  this  point,  the  ground  is  traversed 
by  several  north-and- south  faults,  and  the  beds,  in  some  cases,  have 
been  shifted  a  considerable  distance.  In  the  first  half-mile  the 
diabase  is  not  visible,  the  surface  of  the  ground  being  partly  covered 
by  swamp ;  then  there  is  a  portion  of  the  sheet  of  diabase  exposed, 
about  220  yards  in  length,  but  it  has  been  shifted  about  one-third 
of  a  mile  to  the  north.  Still  proceeding  eastward,  the  next  exposure, 
about  300  yards  in  length,  has  been  shifted  back  about  300  yards 
to  the  south,  and  the  next  exposure  eastward,  which  is  about  200 
yards  in  length,  is  on  the  normal  line  of  strike  of  the  diabase,  while 
the  most  easterly  exposure,  which  is  about  350  yards  in  length,  has 
been  shifted  half-a-mile  to  the  north. 
The  contour  of  the  ground  along  the  strike  of  the  intrusive  sheet 
of  diabase  is  very  irregular ;  the  most  westerly  exposure  occurs  at 
an  elevation  of  about  180  feet  above  Bassenthwaite  Lake,  or  406 
feet  above  sea-level.  From  this  point  the  ground  rises  rapidly  to 
an  elevation  of  750  feet;  thence  there  is  an  almost  equally  rapid 
descent  to  the  level  of  Tarn  Nevin,  450  feet ;  then  another  rapid  rise 
to  700  feet  above  sea-level. 
The  rocks  associated  with  the  diabase  consist  chiefly  of  soft 
Skiddaw  Slate  of  the  ordinary  type,  but  there  are,  interstratified 
with  it,  some  thin  beds  of  grit.  The  dip  of  the  strata  is  at  a  high 
angle,  being  generally  from  15°  to  20°  S.E.,  but  occasionally  it  is 
reversed,  and  at  one  point,  near  the  summit  of  the  hill,  the  dip 
is  about  25°  N.W. 
Like  the  dioritio  picrite  of  White  Hause  and  Great  Cockup,  the 
intrusive  diabase  at  Robin  Hood  is  shown  on  J.  Clifton  Ward’s 
Geological  Map  of  the  Northern  Part  of  the  English  Lake  District 
