Environmental Engineering Reference
In-Depth Information
(a)
Aureole
Sill
Aureole
(b)
HVC
HVC
To p
Paleocene
Base Pg
Sill
Sill
Sill
Figure 12.7 (a) A 60-m sill and the associated contact aureole in Horsedal on
Northern Jameson Land, East Greenland. The sill was emplaced about 56 Ma just
above the Triassic
Jurassic boundary in shales near the base of the Lower Jurassic
Kap Stewart Formation. (b) Two-dimensional seismic re
-
ection pro
le from the
Vøring Basin showing sills and HVCs.
et al
.,
2003
). The borehole data show that the in
ll of the eye is undercompacted, with
unusually high porosities. The undercompaction is likely due to high pore pressure
in the crater sediments maintained by vertical seepage of
fluids in the vent complex
since the earliest Eocene. Pipe-like vertical zones of disturbed seismic re
ections
connect the eye with underlying sills. Commonly, the craters of the HVCs are located
directly above the termination of transgressive sills at depth (Planke
et al
.,
2005
).
12.3 Sill and aureole volumes
Vast volumes of sedimentary rocks are heated in volcanic basins following sill
emplacement (
Figure 12.2
). Sills may extend laterally over several hundred kilo-
metres and commonly have thicknesses of 50
-
150 m (
Figure 12.7
). The volume of
