Causal domain of Minkowski-spacetime tangent bundle

The geometry of the causal domain of the spacetime tangent bundle is examined for Finslerian quantum fields in Minkowski spacetime. The Planck-scale structure of the boundary of the causal domain is elaborated. The geometry indicates that at the Planck scale, causal connectivity of Finslerian quantum fields may occur between spacelike separated points, and also at larger scales for extremely large? relative four-velocities.