| |
|
|
Augering
Augering is the use of drill-like tools to take small samples or columns of sub-surface deposits. These are also
known as 'cores' or 'boreholes'. The advantage of hand augering is that it is fairly quick and easy to carry out,
in comparison to more extensive excavation. It can be used to test the depth of deposits, or to retrieve material
for further analysis.
One auger hole may answer specific questions, such as 'how deep is this ditch, and what type of deposit is at the
bottom?', but when carried out over an area at regular intervals, an 'auger survey' may give a very useful preview
of the types and depths of deposits which may be encountered in subsequent information. These observations can be
used to create a 3-dimensional computer model of sub-surface layers. The disadvantage of augering is that it gives
almost no contextual information about the samples retrieved: for example, an auger may penetrate a grave-cut or the
floor deposit of a prehistoric round-house, but a slight smear of different-coloured soil may be all that would be
visible in the auger sample.
A hand auger is a narrow cylindrical metal instrument used for drilling down into the ground. At the top is the
handle (most often a T-bar which can be twisted to achieve better downward thrust). The shaft is made up of regular
lengths (usually 1 metre), which can be extended to as many sections as are available (over 10 metres, the
structural stability of the auger may become progressively weaker as more sections are added). The most common
types are simple core augers (which have a vertical slit in the shaft which collects soil); screw augers
(which have an Archimedes-type screw for drilling into and collecting the soil) and 'dutch head' augers that have a
separate head which bites out and retains a lump of soil.
More elaborate and deeper-probing augers (which are more often used in connection with engineering than with
archaeology) use a cylindrical metal casing which is hammered into the ground before the core is removed.
These use petrol motors, and in larger cases mechanical 'boring rigs' to drive the equipment into the ground.
However, these can be of use to archaeologists - the results of engineering surveys (which give soil profile across
an area such as a site designated for construction or quarrying) can tell the archaeologist where archaeological
deposits are likely to exist.
Return to Stratigraphy.
|
|
|
 |
