Benjamin Koster

Identifying sedimentary structures and spatial distribution of tsunami deposits with GPR - examples from Spain and Greece

Shallow drilling in coastal areas like southern Spain and different parts of Greece (Corinth region and Argolis Gulf) proved evidence for tsunamis. Sedimentary analyses were conducted to identify tsunamigenic deposits, but did not reveal sedimentary structures or spatial distribution of tsunamites in a regional scale. Since drilling is time-intensive and expensive (depending on extend), this method can by far not cover an entire coastal area. On the other hand, distribution and preservation of tsunamigenic deposits seems to be highly variable. We used ground penetrating radar (GPR) in combination with electrical resistivity tomography (ERT) measurements and sedimentological research methods for tsunamite detection in Greece and Spain. The combination of these three methods enables an improved interpretation of the results and 3D visualization, which give clues for tsunamite distribution and sediment architecture. GPR data indicate unconformable thicknesses of tsunamigenic beddings, channel-like structures (back wash deposits), in some extent chaotic erosion basement, as well as abrasion-scours in various places, and boulder accumulation inside the deposits. In the future, GPR and other shallow geophysical methods will be used to detect run-up distances and typical sediment structures.

The use of ground penetrating radar (GPR) in the investigation of historical quarry abandonment in Svalbard

This paper investigates historical quarry abandonment in Svalbard in the European High Arctic. A short-lived British marble quarry in Kongsfjorden lay deserted after 1920. We ask why this attempt at the large-scale development of High Arctic marble was unproductive; whether there are structural features that affected the known historical trenches and boreholes; and whether the reason for abandonment was primarily geological. During interdisciplinary fieldwork rooted in industrial archaeology and structural geology, we employed medium-resolution ground penetration radar (GPR) to discern subsurface disturbances near the workings. Seven survey grids gave rise to both areas of fracturing and folding as well as areas of sound marble. Using complementary historical documents, we are able to dispel the myths that permafrost or shattered surface rock affected workability and profitability. Although structural disturbances were present, bedrock geology was, in fact, less important than the proportion of waste rock to marketable product. Whether a product was marketable depended on a multitude of other factors. This paper moves away from oversimplified reasoning in mining history and promotes the bridging of geological and historical scales in order to understand the full suite of local and global driving forces in the historical process.