Abstract
The onshore and offshore clastic deposits of the Argive Basin and the Argolic Gulf, respectively, in Peloponnese, Greece, form a Late Neogene–Quaternary half-graben that connects with the Aegean Sea. The onshore Late Neogene–Quaternary sequence, comprised of chaotically intercalated cohesive and granular clastic deposits, is in angular unconformity with bedrock comprised of Triassic–Upper Cretaceous strongly-weathered, highly-fractured karstic limestones thrusted against Paleogene flysch deposits. While the surface geology of the Argive Basin is well-known, the subsurface geology remains both poorly mapped and understood. We utilized transient electromagnetic (TEM) soundings coupled with 185 vintage stratigraphic logs, current surface geology knowledge, and insights from available geophysical surveys to characterize the subsurface conditions of this sedimentary basin. We estimated the thickness of the young deposits (the depth to bedrock) and detected potential subsurface tectonic structures. The TEM-FAST 48HPC data acquisition system with integrated inversion and visualization software package was used with a single-loop dimension of 50 m × 50 m to collect a total of 329 TEM soundings at 151 stations scattered throughout the basin. The TEM station spacing varied from 200 to 750 m allowing the mapping of 80 km2. The total depth of investigation with the inverted TEM data and the lithology logs was 130 m and 183 m, respectively. The joint interpretation produced several quasi-two-dimensional electrical resistivity profiles that traverse the sedimentary basin in various azimuths and depth slices of average electrical resistivity covering the basin. The depth slices and the vintage stratigraphic logs revealed an uneven bedrock topography overlain by an irregularly thick (over 180 m) Late Neogene–Quaternary heterolithic sediment cover.
Highlights
The resulting 1D inverted resistivity models from the 142 transient electromagnetic (TEM) sites were stitched and interpolated with the TEM-RES software to create several quasi-2D electrical resistivity sections with lengths spanning from ~5 to ~17 km long and combined into a quasi-3D model, from which resistivity values were extracted from four depth intervals, namely 0–10 m, 20–50 m, 50–100 m, and 100–130 m
1D TEM et inversion agree thethe known thickness ofresistivity the sedimentary sion of the TEM soundings yield an electrical resistivity range from
One hundred and forty-two 1D inverted resistivity models from TEM soundings coupled with 185 vintage stratigraphic logs and available upfront geological and geophysical information were instrumental in characterizing the subsurface conditions of a young sedimentary basin
Summary
Transient electromagnetic (TEM) surveys have effectively mapped the electrical resistivity structure of various Late Neogene–Quaternary sedimentary basins of distinct depositional environments (Soupios et al [1,2]; Vallianatos [3]; Koutsios et al [4]; Kanta et al [5]; Mollidor et al [6]; von Papen et al [7]; Yogeshwar et al [8]; Kourgialas et al [9]; Autio et al [10]; Demirci et al [11]; Kalisperi et al [12]; Rani et al [13].) TEM data can be used to correct static shifts in magnetotelluric data surveys (Ruiz-Aguilar et al [14]). The interpretation of drillhole lithologic data provides an approximate three-dimensional (3D) stratigraphic framework (Amorosi et al [15]; Sweetkind et al [16]; Taylor and Sweetkind [17]; Sweetkind and Drake [18]). Its beaches and world heritage archaeological sites attract international tourism and researchers
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