Archeological
Investigations:
Discovering Mankind's Hidden Secrets
For
the past 14 field seasons, Dr. Tatyana Smekalova, Physical Institute
of the St. Petersburg State University, Russia, has contributed
to numerous archeological projects in the search to discover
the secrets of man's past history. Her work has taken her and
her colleagues to sites in Armenia, Denmark, Egypt, Estonia,
Germany, Greece, Norway, Russia, Sweden (Skane), Syria, Turkey,
Ukraine (Crimea), and Wales. It's a world of adventure ... and
a world in which magnetics plays a key role.
Dr.
Smekalova at work with a GSM-19
and sensor carried in inverted position
for proximity to near-surface sources.
As
noted by Dr. Smekalova, "magnetometer surveys are one of
the most effective and universal among geophysical methods for
archaeological applications. Many objects can be readily distinguished
at surface according to the characteristic anomalies associated
with them. Magnetic prospecting (in favourable conditions) has
also proven itself as the most effective, fast and non-destructive
method for the investigation of archaeological sites. As well,
the information obtained is very similar to that revealed during
archaeological excavations."
The
reasons for the effectiveness of magnetics in archeology are
related to several factors, including alteration of magnetic
properties due to fire and magnetic susceptibility contrasts
in soils. The image below shows some of the anomalies associated
with various magnetic artifacts.
In
ancient days, the use of fire for heating, cooking, production
and industry changed the magnetic properties of clay, stones
and earth - to the extent that they can be readily mapped using
magnetometers. Earthen structures typically exhibit local magnetic
anomalies in the range of 1-20 nT whereas "fired"
structures can range between 10 to 1000 nT. Ferrous objects,
including iron-smelting slag blocks, are rarer with anomalies
that range between 20 to 2,000 nT.
Variations
in magnetic susceptibility between topsoil, subsoil and rocks
(topsoil is normally more magnetic than subsoil) are another
important factor. These variations make it possible to detect
ditches, pits and other silted-up features that were excavated
and then silted or back-filled with topsoil. Back-filled areas
produce positive anomalies. Conversely, less magnetic material
introduced into topsoil, including many kinds of masonry (for
example, limestone walls) produce negative anomalies on the
order of 2 to 12 nT.
Dr. Smekalova
uses a variety of systems, including:
- Overhauser
gradiometer GSM-19WG
as a main instrument
- Cesium
magnetometer MM-60 (Russia, St. Petersburg)
- Proton
magnetometer MMP-203 (Russia, St. Petersburg)
Results
are documented in a publication, called "Magnetic Prospecting
in Archeology" that shows results from many types of sites,
including:
- Flint
mines
- Stone
Age barrows
- Cooking
pits
- Iron
smelting sites with slag pits
- Early
Iron Age sites
- Ancient
fortifications
- Medieval
pottery kilns
- Islamic
fortresses and cemeteries
You can
access Dr. Smekalova's case histories by selecting from the
list below. These resources provide a fascinating look into
some of the artifacts left by our ancestors in many parts of
the world, and are filled with many examples of geophysical
data, ancient maps and artifacts.
Resources
made available courtesy of Dr. Tatyana Smekalova. All rights
reserved.
