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To
the Carboniferous of the Fife Coast, Scotland. FULL
Instructors: Mark Lawrence, Steven Fayers,
Edmund Smith (Baker Atlas GEOScience, Aberdeen, UK)
Date: Saturday 24th May 2008
Time: 0730-1930 hours (approximately)
Fee: TBA (Includes transportation, lunch,
beverages, guidebook)
Sponsor: Baker Atlas GEOScience.
Participant numbers will be limited to 50 persons. FULL
Outcrop localities are on the southern coast of
Fife, Scotland, approximately 77 km (48 miles) by
road north of Edinburgh. The rocks that will be
examined are of Carboniferous age (circa 330 million
years old), and were deposited as part of a large
delta system, probably under humid, tropical
conditions. These deposits, along with similar but
thicker and more extensive formations in the west of
the Midland Valley of Scotland and in northern
England are onshore analogues for Carboniferous gas
reservoirs of the Southern North Sea Gas Basin. In
addition, Carboniferous rocks are also a significant
hydrocarbon source in the North Sea. The aim of this
excursion will be to illustrate a wide range of
lithologies and structures and their effect on log
response. Wherever possible, comparisons of outcrop
observations with open-hole (and a few LWD) logs,
particularly examples of borehole images will be
made.
The outcrops to be examined occur in the upper part
of the Strathclyde Group and Lower Limestone
Formation. Successions comprise fluvial-lacustrine
to fluvial-deltaic sediments that were subject to
fluctuations in relative sea level. This resulted in
formations comprising stacked intervals that are
commonly marine-dominated at the base, with deposits
comprising limestones and marine mudstones that
contain a range of trace and body fossils. The
limestones are composed primarily of crinoidal
debris with significant clastic mud, although one
limestone contains in-situ corals (Figure 1) and is
stylolitized and dolomitized. Overlying the marine
sediments are rippled to cross-stratified sandstones
and mudstones that are commonly capped by coals or
palaeosols (Figure 2). The sandstones range from
possible fluvial channels to bar deposits of
potential terrestrial to estuarine origin. This
lithological heterogeneity produces a wide range of
open-hole log responses.
During the late Carboniferous the area was subjected
to episodes of faulting and folding. Fractures,
faults and folds are clearly visible at various
scales as is their effect on potential reservoir
heterogeneity. These tectonic features appear
associated with the intrusion of igneous rocks and
probably provided pathways for rising magma. The
result is a variety and abundance of volcanic dykes
and local extrusives. The effect of volcanism on
reservoir quality can be examined at some
localities.
The field trip is
designed to suite both specialist geologists and
non-geologists. The excursion will be on foot along
the beach platform and coastal path for about 10 km
(6 miles) so a moderate level of fitness will be
required (we will not climb any higher than about 60
m). Stout footwear (sturdy trainers at least) will
be required and participants should be prepared for
inclement weather (rain and cold conditions are
always a possibility). Lunch will be provided at the
half-way point, in a suitable hostelry identified on
previous excursions.
Figure 1:
Large in-situ coral (possibly Lithostrotion) in a
fossiliferous limestone.
(Photo Mark
Lawrence).
Figure 2:
Faulted fluvial-deltaic sandstone, mudstone and
coal.
(Photo Mark
Lawrence).
Click here for more information and pictures.
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