58 
MISS  OGILYIE  ON  THE  WENGEN  AND 
[Feb.  1893, 
VIII.  The  Tectonic  Relations. 
(See  General  Tectonic  Map,  facing  p.  70.) 
Before  entering  into  a  detailed  consideration  of  the  geological 
maps,  it  is  perhaps  advisable  to  refer  to  the  general  tectonic  relations 
of  the  northern  district  of  the  Dolomites ;  the  three  separate 
districts  which  I  have  specially  studied  will  thus  be  more  clearly 
brought  before  the  reader.  My  own  knowledge  of  this  wider  region 
is  based  on  a  study  of  the  literature,  as  well  as  on  personal  obser¬ 
vations  in  several  places. 
A  glance  at  a  geological  map  of  the  Dolomites  shows  that  the 
pre-Triassic  rocks  are  exposed  in  the  Pusterthal,  and  are  succeeded 
in  the  south  by  younger  strata.  In  the  neighbourhood  of  Prags, 
west  of  Toblach,  we  meet  Werfen  and  Muschelkalk  beds;  these 
continue  westward  in  the  Hoch  Alpe  towards  St.  Vigil  and  Wengen, 
and  cross  the  Enneberg  Valley  north  of  Pedratsches.  Here  they 
bifurcate,  the  northerly  branch  passing  off  in  the  Villnos  direction, 
the  southerly  over  the  valley  of  Campil  to  that  of  Groden.  From 
the  Groden  Valley  it  turns  southward,  and,  leaving  Schlern  on  the 
east,  is  exposed  in  the  Tiers  Valley  and  farther  south.  The  same 
strata  strike  along  the  base  of  the  liosengarten  massif  and  the  Fassa 
Valley,  eastward  over  the  Pordoi  Pass  into  the  Buchenstein  Valley  ; 
from  Buchenstein  they  strike  south-west  towards  Caprile,  where  they 
are  in  great  measure  lost  sight  of,  owing  to  an  east-and-west  fault¬ 
line,  but  may  be  partly  traced  as  far  as  St.  Vito  in  the  Boita  Valley. 
Within  these  limits  the  older  Triassic  strata  are  nowhere  ex¬ 
posed,  with  the  exception  of  a  small  band  from  the  Upper  Groden 
Valley,  over  the  Groden  Pass  to  Colfuschg  and  St.  Cassian.  The 
younger  Triassic  strata  attain,  on  the  other  hand,  an  extended  out¬ 
crop,  so  that  in  a  merely  general  sense  we  may  regard  this  as  a 
synclinal  area,  in  which  at  one  part  (Groden  Pass — Langs-da-fur 
— St.  Cassian)  the  older  beds  form  a  broken  anticline.  This  folding 
of  the  beds,  although  indicated  on  a  broad  scale,  has  been  modified 
and  sometimes  entirely  destroyed  by  a  number  of  faults. 
Hot  many  miles  distant  from  the  outer  zone  of  older  Triassic 
strata  there  rises  abruptly  a  great  complex  of  Dachstein  Dolomite, 
succeeded  in  many  places  by  Jurassic  and  Cretaceous  rocks.  This 
Dachstein-Dolomite  complex  embraces  Hohe  Gaisl,  Seekofl,  Heilig- 
kreuz  Kofi,  La  Varella,  Tofana,  Monte  Cristallo,  and  one  may  add 
Gardenazza  in  the  west.  Numerous  faults  have  let  down  this 
whole  region  of  Dachstein  rock,  and  it  is  perhaps  better  to  speak 
of  it  as  a  subsided  area  than  as  a  syncline.  In  many  of  the  sections 
given  by  Mojsisovics  (‘  Dolomit-Biffe,’  pp.  209,  213,  288,  289,  etc.) 
the  lines  of  disturbance  and  faulting  are  shown. 
The  relations  in  the  outer  zone  of  older  Trias  vary.  At  many 
places  (e.  g.  the  Diirrenstein,  Wengen  district,  Puflatsch)  the  older 
Triassic  strata  are  let  down  by  step-faults,  whereas  in  the  neighbour¬ 
hood  of  Pedratsches  they  are  folded. 
Of  more  importance  are  the  faults  which  have  brought  down 
the  younger  Triassic  against  this  zone  of  older  Triassic  rocks. 
