Geoscience Reference
In-Depth Information
not required, except of course to be able to place the beds in
stratigraphic order and to compensate for any displacement.
Before you go into the fi eld, decide on the overall objectives of
the fi eldwork and at frequent intervals during the fi eldwork
remind yourself of these. On a day-to day basis in the fi eld,
break the work down into achievable tasks; these may need to
be reviewed and amended if the weather or time available
changes. Another important point to remember is not to
overinterpret the rocks based on a single observation. Instead
combine as many lines of evidence as possible in order to put
together one or more hypotheses. Write down the questions
that each hypothesis raises, and think about what other data
you need to collect or fi nd in the literature to distinguish
between these competing working hypotheses. Almost all of the
geological record is incomplete so there are only ever a series
of clues about what happened in the past.
3
The common overall objectives of fi eldwork are summarized in
Table 3.1 (p.
44), which also provides reference to the chapters
where there is further information both on the techniques and
how to tackle the objectives. Specifi c day-to-day activities to
achieve these overall objectives will be tasks such as: explore a
particular region for new exposures; collect data on certain
units; map a particular area; collect samples; or check data
collected on the previous day.
3.1.2 Deciding where to do the fi eldwork
The amount and type of rock exposure varies according to
climatic zone - from almost 100% in arid areas to almost
nothing in heavily vegetated areas such as the tropics. Provided
they are safe and accessible, sea-cliffs, working quarries and new
road cuts provide some of the best exposures because of the
amount of rock exposed and their unweathered nature. Stream
and river sections can also be important. If you are going into a
fi eld area for the fi rst time and do not have a specifi c set of
locations to visit based on published information from previous
research on the area, spend a few hours or days completing a
reconnaissance of the area to fi nd the exposures that are most
suitable for the objectives of the fi eldwork. Table 3.2 (p.
45)
provides a list of the types of places to search for suitable
exposures. If you are completing detailed mapping then all
exposures need to be considered, unless there is 100% exposure
in which case traverse or contact mapping are more appropriate
(Sections 10.5.1 and 10.5.2 respectively). To address all other
fi eldwork objectives, the following points are worth considering
when choosing the exposures to concentrate on:
•
whether or not they are representative;
•
stratigraphic completeness;
