Magnetic survey

Geophysical prospection in Novae is a hard task due to inaccessibility of most important areas of civil settlement and hard topographical and geological conditions. Yet systematic and carefully planned survey campaigns produce results that can be the base for further interpretation.

Due to dense forestation of the fort’s territory and development of modern summer housing around it’s area a wide scale approach for magnetic survey had to be adjusted to conditions present on site. Areas with the best accessibility offering the widest, open area suitable for prospection have been chosen as primary for the study. This suitable area is situated in the southern part of the fort, forming a wide post-agricultural belt that stretches from east to west.  It is possible to identify this accessible area as retentura – the rear part of a camp behind the praetorium,  as well as the southern part of the so-called eastern annexe.

Prospection in hard surface conditions

Prospection in rough surface conditions

The prospection is being carried out with the use of a fluxgate magnetometer, Bartington Grad 601-Dual. Prospection grids are pre-designed and adjusted in size and layout to the surrounding in order to maximise the extent of measurement cover.

In 2011 initial magnetic prospection on the area of the retentura has been carried out in order to determine whether its application produces successful results. After positively verifying the use of this method the survey has been extended on the full accessible terrain of the eastern annexe (season 2012) and finally the gaps between both survey areas have been filled (season 2013).

canabae2012

Areas covered by magnetic measurements in 2011-2012

On the eastern annexe a survey grid of 30 × 30 m polygons (23 in all) was laid out covering ​​over 2 ha. Magnetic prospection in 2012 was conducted with a Bartington Grad 601-Dual fluxgate gradiometer and a cesium magnetometer G-858 Magmapper with GPS RTK. A micro-relief map covering the area inside and outside the walls was also made with the help of the GPS RTK system.

The survey revealed a number of different types of anomalies which correspond to features visible on the surface and subsurface ones, including ancient architectural structures. We can distinguish linear anomalies, zones of interference, dipolar and single point positive anomalies. Surface features manifested in the form of characteristic linear, parallel anomalies include rows of stones, some of which reveal tooling marks. They could be a remnant of ancient retaining walls forming a system of leveling terraces, or modern parceling of arable fields – their origin is up to date the subject of investigation.

Magnetic prospection on Ostrite Mogili site

Magnetic prospection on Ostrite Mogili site

Linear anomalies intersecting at a right angle can be connected with buried remains of ancient buildings. Further studies, using complementary methods (e.g. ERT and earth resistivity) will allow for a more accurate and deeper understanding of the underlying stratigraphy and should determine the nature and origin of the anomalies. This will allow to precisely locate architectural features of the “eastern extension”.

A few other magnetic anomalies can be linked with features seen on the surface. The largest of these is a zone of disturbance caused by modern infrastructure and treasure hunting activities. Illegal digs are undertaken on such a scale that they can be seen even on satellite imagery.

In the season of 2013 magnetic prospection has been additional carried out on the site of Ostrite Mogili, east of the fort. Measurements have been conducted in a relatively open area, yet crossed by series of metal fences. The survey area covered around 3 ha revealing a series of anomalies that might suggest presence of subsoil architectural remains. Further studies aided by ERT and earth resistivity should produce more comprehensive data for interpretation.

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