The purpose of this
final chapter is to demonstrate how the techniques for separation and
identification of microfossils, and knowledge of their stratigraphic ranges and
ecologic significance, are applied to geological problems by economic
geologist. Some of the applications have already been mentioned, particularly
in the chapter on environmental significance of microfossils. The present
chapter will briefly discuss additional applications of micropaleontology to
prospecting for petroleum, because it is the oil companies that today make the
widest use of micropaleontology. In fact, much of the advance in our knowledge
of the subject is due to the work of commercial micropaleontologist.
Micropalentological
information is used to establish the following types of information concering
sedimentary rocks in the subsurface:
1.
The
geological age of a given subsurface section
2.
Stratigraphic
datums, or makers, whose stratigraphic position in relation to oil bearing
strata aids in drilling “wildcat wells” in unproven territory
3.
Stratigraphic
correlation from to well, and from area to area, on the basis of the
micropaleontoloical marker horizons.
4.
The
sedimentary environment in which a given lithological entity or sequence was
deposited; this information is obtained by intelligent correlation of the
microfossils of s given stratum with its containing lithology
5.
Tectonic
activity in sedimentary basins as reflected by oscillations of the water depth.
This is inferred from careful interpretations of the ecological significances
of microfaunas. The tool used un this type of environmental reconstruction is
the oscillation chart.
