Page 85 - Sedimentology and Stratigraphy

72 Field Sedimentology, Facies and Environments

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Fig. 5.2 Examples of patterns and symbols used on graphic sedimentary logs.

By convention the symbols used to represent sedi- simply written alongside the graphic log in an appro-
mentary structures bear a close resemblance to the priate place.
appearance of the feature in the field or in core
(Fig. 5.2). This representation is somewhat stylised
for the sake of simplicity and, again, symbols can be 5.2.2 Presentation of graphic sedimentary
adapted to suit individual circumstances. Where logs
space allows symbols can be placed within the bed
but may also be drawn alongside on the right. Bed It is common practise to draw a log in the field and
boundaries may be sharp/erosional, where the upper then redraft it at a later stage. The field log can be
bed cuts down into the lower one, or transitional/ drawn straight on to a proforma log sheet (such as
gradational, in which there is a gradual change Fig. 5.3), but it can be more convenient to draw a
from one lithology to another. Any other details sketch log in a field notebook. The field log does not
about the succession of beds can also be recorded on have to be drawn to scale, but the thickness of every
the graphic log (Fig. 5.1). Palaeocurrent data may bed must be recorded so that a properly scaled version
be presented as a series of arrows oriented in the of the log can be drawn later. Sketch logs in the field
direction of palaeoflow measured or summarised for notebook are also a quick and convenient way of
a unit as a rose diagram (5.3.3) alongside the log. recording sedimentological data, even when there
Colour is normally recorded in words or abbreviations are no plans to present graphic logs in a report. As
and any further remarks or observations may be is usually the case in geology, sketches and graphical