Geoscience Reference
In-Depth Information
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qualitative and quantitative data on ancient climates, and a
method of testing the applicability of climate models for a
range of climatic modes;
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the basis of relative dating and correlation of rock units;
some megafossils* are currently the only method by which
rocks can be given a relative age in the fi eld (other than
superposition and cross-cutting);
5
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information on the biotic and chemical conditions
following the death of the organism, at the time of burial
and subsequently through its burial history - these data are
important for determining, for example, the hydrocarbon
potential of a rock unit.
5.1.2 Collecting fossil data
For fossils visible to the naked eye careful observation of
morphology, preservation mode, orientation, context in terms
of other fossils (assemblage characteristics), stratigraphic
position and relationship to the entombing sedimentary
deposits are all fundamental to successful palaeontological
interpretations. The three-dimensional nature of both body and
trace fossils often presents a challenge in recognizing the type
of fossil. It is important to record the orientation and to become
familiar with the characteristics of a variety of sections through
the fossil. The best items of fi eld equipment for recording
fossils are:
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a notebook in which to make sketches;
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a hand lens to examine detail;
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a camera.
In general, fossils, rather than being removed, are far more
valuable left in place for others to see and interpret. The
location and sedimentary context of a fossil is of paramount
importance. Fossils with no contextual or provenance
information are of little value except for their aesthetic
qualities. The term 'provenance' here includes not only the
geographical location, but also information on the stratigraphic
position as well as the nature of the sedimentary succession
and individual sedimentary facies that surround it. Ideally this
should mean constructing a sedimentary log of the succession
with fossil data included (Section 6.3).
*The term megafossils indicates large fossils that are easily distinguished with
the naked eye (compared with microfossils which are not easily distinguished).
Megafossils are also sometimes termed macrofossils but, technically, the term
macro only refers to length so it is incorrect.
