Is it possible to have a vein layer as top layer?

I've developed a Leapfrog model to analyze the stability of a tailings dam. The model represents two top green layers as tailings, which have been modeled as vein. The underlying purple layer is sediments, modeled as a deposit. In the model, the tailings (modeled as vein) are expected to form the top layer. However, the model reveals an unexpected interaction where the characteristics of the underlying coarse-grained sediments seem to exert an influence on the overlying tailings layer. This effect is disrupting the expected stratigraphy and is not representative of the actual conditions I'm trying to model. I'd appreciate any insights or suggestions on how to address this issue. Can I remove this effect from green and white veins?