  Dephasing in quantum systems is typically the result of its interaction with
environmental degrees of freedom. We investigate within a spin-boson model the
influence of a super-Ohmic environment on the dynamics of a quantum two-state
system. A super-Ohmic enviroment, thereby, models typical bulk phonons which
are a common disturbance for solid state quantum systems as, for example, NV
centers. By applying the numerically exact quasi-adiabatic path integral
approach we show that for strong system-bath coupling, pseudo-coherent dynamics
emerges, i.e., oscillatory dynamics at short times due to slaving of the
quantum system to the bath dynamics. We extend the phase diagram known for
sub-Ohmic and Ohmic environments into the super-Ohmic regime and observe a
pronounced non-monotonous behaviour. Super-Ohmic purely dephasing fluctuations
strongly suppress the amplitude of coherent dynamics at very short times with
no subsequent further decay at later times. Nevertheless, they render the
dynamics overdamped. The according phase separation line shows also a
non-monotonous behaviour, very similar to the pseudo-coherent dynamics.
