Geoscience Reference
In-Depth Information
The sea-cliffs at Osmington Mills, near
Weymouth, Dorset, UK show a marked facies
change from micritic limestones (biomicrite) to
oolitic grainstones (oosparite). The base of the
oolitic grainstone facies is erosional and down-
cuts towards the west. The objective of this fi eld
exercise was to gather evidence for the erosive
nature of the contact and to interpret its possible
origin. The photographs show both an overview
(Figure 6.15a) and a close up view along the
section (Figure 6.15b). Accompanying sketches
or line drawings (Figure 6.15) can be used to
show the large-scale geometry of this important
surface. A graphic log was constructed (Figure
6.16) where this section was interpreted to be at
its most stratigraphically complete. This erosive
contact has been interpreted as a sequence
boundary on the basis of the erosion at this
location, and others across the basin, together
with evidence from sections in the Cleveland
Basin to the north, where there is also a sharp
facies change.
6
Figure 6.16
Extract from
a published graphic log of
the most complete part of the
succession across the
sedimentary contact shown in
Figure 6.15. (From Coe
1995.)
6.6 Further reading
Alexander, J. 1992. Nature and origin of a laterally extensive alluvial
sandstone body in the Middle Jurassic Scalby Formation,
Journal of
the Geological Society, London
,
149
, 431-441. [Summary paper of
the Middle Jurassic succession described in Worked Example 6.1]
