The basement structure below the peat–lignite deposit in the Philippi sub-basin (Northern Greece) inferred by electromagnetic and magnetic methods

Abstract

During 2009 and 2010 electromagnetic (EM) soundings and a high-resolution magnetic survey were conducted to study the deeper structure of the peat–lignite deposit in the Philippi sub-basin in Northern Greece. The primary intention of investigating the basement structure of the Philippi sub-basin is to propose the ideal location for a deep and continuous paleoclimate drill site.Data were collected along a 12km transect (NNE–SSW) through the largest extension of the basin from Krinides at the North to Eleftheroupolis at the South. We used a combined set of Radiomagnetotelluric (RMT), Time Domain Electromagnetic (TEM) and Audiomagnetotelluric (AMT) soundings to derive a 2D model of the electrical resistivity distribution versus depth using a joint inversion approach. This model was then cross correlated with a 2D forward model of magnetic anomaly data. The magnetic survey detected strong anomalies in the North that appeared to have been generated by the Philippi granitoid pluton. All three individual data sets support each other and have jointly been analyzed. From this study we yield an asymmetric graben model of the basin structure that shows maximum thickness (ca. 500m) in the northern part of the basin leading to a reduction of the thickness to the South. The interface between the basin fill and the bedrock ascend steeply in the North. The overall assessment of the deeper basin structure reveals a detachment system that is in good accordance with previous findings.