Symptom:
When creating erosion surfaces, an additional surface was improperly created many miles away from the main Lithological unit. There is no additional data such as polylines, points etc that are in the area.
Resolution:
Altering the resolution or changing any other input criteria, will change the iteration process and may result in the artifact no longer appearing and a more acceptable mesh being produced.
Applying trend by adjusting the Ellipsoid Ratios slightly on the Trend properties tab to 1.2; 1.2; 1 may also remove the additional surface.
Root Cause:
This is a known issue that happens from time to time with surface creation. The way the surfacing algorithm works is that it iterates through a selection of possible meshes (with a maximum of 200) that will fit the criteria laid out by the user in the mesh settings when a mesh meets all the criteria the mesh is built. On a rare occasion, the mesh meets the acceptance criteria first, causing some artifacts. This is most commonly seen in surfaces that have a lot of input data that have a fairly complex geometry. Because the surface algorithm looks at all the drill hole data when building a surface the artifacts can at times appear a large distance away from the actual contact as the surface tries to grapple with the complex data.
Notes:
This is an issue that is currently being investigated by the development team and you can be assured that this is a very rare occurrence, where only a handful of projects have reported an issue like this.