Geophysical Investigation of Babylon archeological City, Iraq

Abstract

A geophysical survey was carried out at old archeological Babylon City, which is located 90.0 km to the south of Baghdad. Three geophysical methods were applied in this survey. The VES resistivity method, for soil conductivity and layering testing. GPR and magnetic methods, for detecting subsurface archeological bodies. The resistivity results showed values lower than 5.0 ohm. m, and subsurface distortion, which are probably related to buried archeological ruins. Due to the low electrical resistivity of the top soil, the GPR method did not reach a good penetrating depth. Wide range of frequencies, 30 MHz, 250 MHz, 500 MHz, and 100MHz were applied. The high signal attenuation of the top soil resulted in distorted radar-grams with faint shallow anomalies. The GPR survey was conducted at different seasons hoping that the dry conditions of the hot summer could change the top soil electrical resistivity. Nevertheless, few GPR radar- grams show point reflections that related to small dense bodies at depths of 0.8 – 2.0, which could be archeological bricks walls. The magnetic survey was carried out in two stages using Cesium magnetometer of high sensitivity. An area of 140.0 m x 240.0 m was surveyed at the first stage, which is covered by twenty-eight N-S traverses. The preliminary results show the effects of the N-S profiling, which can be removed by directional first derivative filter. It showed indications of subsurface archeological features. In the second stage, an area of 40.0 x 40.0 meters was chosen for detailed survey. The survey is done a long 40 traverses in N-S direction and another 40.0 Traverses along W-E directions. The preliminary results of the both surveys show some differences. These differences were removed by using first derivative filter. They both showed subsurface geometric shapes that are probably related to buried archeological walls. The mathematical modeling results showed walls of widths 0.3-0.4 meters at depths around 0.8 meters. These walls continue down to 2.3-2.5 meters in depth. The magnetic survey also showed many circular high magnetic anomalies within an area of 1.0 – 2.0 meters only. The mathematical modeling suggested that these anomalies could be corresponding to building poles made of andesite or basaltic rocks or they are buried metals objects.