Fróðskaparrit - 01.01.1996, Page 120

TWO-WAY TRAVEL TIME (sec)
124 IMAGING OF BASALT AND UNDERLYING STRUCTURES IN THE FAROESE OFFSHORE AREA
Figure 4. Profile 2, crossing the East Faroe High and descending into the Faroe-Shetland Channel. Description
ofmajor geophysical features given in the text. Also notable is the relative thinning and thickening of the Miocene
and Oligocene units, possibly representative ofthe interactions between uplift, subsidence, and sediment supply.
1. Miocene to recent sediments are the shallowest unit
mapped (blue-green color); although refelctors tend
to be long and continuous, this interval displays the
characteristics typical of Neogene bottom contour
current effects (Boldreel and Anderson, 1995).
2. The Oligocene period is represented by the blue
interval and tends to consist of short, disrupted re-
flector segments, possibly due to the incompetent or
high velocity environment present during deposi-
tion; its upper boundary with the Miocene may be
taken as a diagentic horizon.
3. The Eocene unit (dark orange) is well layered where
present, strongly reflective, and mainly conformable
with the basalt rocks which it overlies. As this unit is
highly positive in its magnetism, it may represent
eroded volcanic material. It appears to correlate with
the Andrew Formation found West of Shetlands and
in the North Sea, where it is a known hydrocarbon
producing unit.
4. The basalt (orange) rocks are delineated from the
overlying units by a sharp, strong acoustic impe-
dance boundary which is readily recognized and can
be correlated throughout the Tertiary Igneous Pro-
vince (Wood, Hall, and Doody, 1988). The intemal
structure is signified by a rather continuous, parallel
bedded nature which is characteristic of subaerially
extruded plateau basalts (Smythe et al, 1983; Wood,
Hall, and Doody, 1988, Boldreel and Anderson
1993).
This line crosses the Faroe-Shetland Escarpment
at wd 1150. The Faroe-Shetland Escarpment is
thought to represent the location of the paleocoast-
line at the time of formation of the basalt (Jones and
Nelson, 1970; Smythe et al, 1983; Boldreel and
Anderson, 1994) where the basalt flows have built
outwards when they are cooled by contact into water.
The basalt flows within the escarpment here have a
slope of 19 degrees when reduced to zero vertical
exaggeration and appear to be quite faulted. It can
also be observed that the basalt unit thins basinwards
of the escarpment; this might represent the transition
from the presence of all three Faroese basalt units as
described in outcrop (Upper, Middle, and Lower
Series, Waagstein 1988) to Lower Series only within
the basin (Smythe et al, 1983; Anderson, 1988).
5. The green unit interval denoted as Subbasalt 1 is
interpreted as the uppermost unit underlying the
basalt. This unit may, in fact, represent older basalt
but there are several factors which preclude this
interpretation:
a. The unit does not display the same genetic plane
parallel bedded character shown in the overlying
orange basalt unit, believed to be subaerial in
nature of formation;
b. Reflector segments are shorter,stronger, infills
the geometries of its basal unit, and shows onlap,
downlap, and truncation features.
c. Internal clinoform segments are steep (in the