Geological Structure and Neotectonic Fabric of the Amyntaio Basin, NW Greece: The Correlation Between Fault Systems and Ground Fissures

This study focuses on the investigation of the geological and neotectonic conditions of the Amyntaio Basin, with a particular emphasis on the recent geological formations that host the region’s primary aquifers. Understanding the stratigraphy and tectonic structure is considered essential, as these formations serve as the primary water source for domestic, agricultural, and industrial requirements. The basin fill consists of thick Neogene and Quaternary sediments deposited unconformably over the Mesozoic basement. Dominating these deposits is the lignite-bearing series, while the overlying Quaternary formations are distinguished into the lower coarse-grained Proastio Formation, characterized by conglomerates and sands, and the upper finer-grained Perdikka Formation, which primarily includes marls and clays. Significant importance is attributed to modern alluvial deposits, which cover most of the basin and directly influence the hydrogeodynamic system. In the central part of the basin, near Lake Chimaditida, up to six-meter-thick layers of peat and organic silt occur, while the northwestern sector is dominated by the extensive alluvial fan of Sklithro.

Structural mapping revealed a dense fault fabric compatible with the current extensional stress regime of the area, dominated by normal faults striking NE-SW to ENE-WSW. The primary structures include the Vegoritida fault zone, which terminates at the northern boundary of the Amyntaio mine, the Chimaditida fault, which is likely connected to the Vegoritida system, and the Anargyroi fault, which defines the southern margin of the sub-basin. The combination of these structures creates a second-order tectonic graben where Lake Chimaditida has developed, while the Amyntaio mine area is situated within a fault transfer zone. Within the mine itself, the tectonic fabric consists of smaller normal faults following the same primary orientation, creating a complex horst and graben system.

One of the main conclusions of this study is the systematic geographical distribution and geometry of the mapped ground fissures. The orientation of these fissures coincides with the primary direction of the regional neotectonic fabric, specifically following the trends of the Petres-Sklithro and Anargyroi fault systems. Their kinematics align with the general tectonic extensional regime, suggesting a clear genetic relationship between active faults and surface ruptures. In certain areas, such as the one west of the mine, between the settlements of Anargyroi and Valtonera, the traces of the mapped faults practically coincide with the observed fissures. Furthermore, the alignment of these outcropping structures, between Valtonera and Rodona, confirms the existence of the Valtonera Fault. This structure constitutes an integral part of the neotectonic fabric and is identified as the primary factor responsible for the magnitude of the ground deformation phenomena within the settlement.