Geoscience Reference
In-Depth Information
logged, the total thickness of strata to be recorded, the time
available and the aim of the logging. Alternatively you could
draw the log to a very rough scale in the fi eld and then
draw it to scale in the neat version. The advantages of not
completing the log to scale in the fi eld are that it allows
you to put the details into very thin beds and to not take
up too much space with thick beds that show few features;
it is also much quicker. The disadvantage is that you do
not have as good a visual record of the beds in the fi eld.
3. Decide where exactly along the exposure you are going to
make your measurements and observations. You need to
ensure that you complete the logging somewhere that is
representative, where you can access the stratigraphy
safely and where beds are not covered by scree or
vegetation. Many exposures are of dipping beds so it may
be necessary to move along in order to examine all of the
beds. As you construct your log you should note any
major changes that occur laterally, for instance if one of
the contacts is erosional and cuts out the underlying beds.
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4. Record the nature of the boundary at the base of the
section to be logged. Note whether it is gradational or
sharp. If it is gradational record over what distance this
occurs. You should also note whether the contact is
planar or undulose. For undulose contacts the nature of
the contact should be noted preferably in graphical form.
5. Decide where the upper boundary of the unit lies. The
'unit' is either a bed or set of beds depending on the
nature of the succession and the scale of resolution
required for the graphic log.
6. Measure the total thickness of the unit, ensuring that you
measure perpendicular to the bedding surface.
7. Record the nature of the contact with the overlying unit.
8. Record the composition and sediment texture information
(lithology) for the unit. Note any changes within the unit
if that scale of resolution is required.
9. Record the sedimentary structures and fossils in that unit.
10. Record any samples or photographs taken.
11. Record any unusual features and/or topographic features
that may help you relocate the unit.
12. Complete any correlation and comparison to previous
work as necessary.
13. Repeat steps 5 to 13 for the next stratigraphically younger
unit and so on, continuing on further pages of the
notebook as necessary.
