GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 71-4
Presentation Time: 9:00 AM-5:30 PM


RAUCH, Anna, SARTORI, Mario and CASTELLTORT, Sebastien, Department of Earth Sciences, University of Geneva, Rue des Maraichers 13, Geneva, 1205, Switzerland,

Geological Maps are crucial to understand the spatial relationships between different geological features. Forming the core of many models (hydrogeological, hazard, structural etc.), geological maps inform decisions across industrial, civil and academic fields. Although they depict the world as accurately as possible, everyone is aware that they are in fact models, interpretations, constructions which are inherently comprised of subjective and non-verified geological concepts. It is therefore not always clear how to judge the quality and reliability of geological maps, especially pre-existing maps. How much information do they contain? Where might information be reliable and where might it be structurally inconsistent?

Inspired by such questions, we are developing a tool that analyses bedrock and structural content in maps. By means of a high-resolution DEM, the tool numerically extracts geometric information from outcropping geological boundaries in 3D, meaning the stretches of interfaces between different bedrock bodies where they intersect with the topography. We name such a stretch of isolated boundary Topography-Interface-Line (TIL). The analysis will determine whether the geometry of the TIL is most consistent with a planar, a curved or a complex (or even “chaotic”) interface. In case of a plane-consistent TIL, one directly obtains a well-confined range of plane orientations that fit the TIL. For a curve-consistent TIL, the degree of curvature is extracted. Also to complex non-consistent (or “chaotic”) TILs a magnitude of irregularity can be attributed. Non-consistent TILS occasionally represent a highly irregular bedrock interface, but more often highlight a poorly located bedrock boundary.

A consistency control based on the objective analysis we have proposed, combined with orientation measurements and geological knowledge, locates and identifies potential inconsistencies or strongly facilitates the extraction of previously hidden structural information. This therefore becomes central to any model interpretation or decision derived from geological maps. Moreover, using our tool while editing new maps might also help make future work more coherent and thus more valuable and sustainable.