  In this paper we examine the decay of quantum correlations for the radiation
field in a two-mode squeezed thermal state in contact with local thermal
reservoirs. Two measures of the evolving quantum correlations are compared: the
entanglement of formation and the quantum discord. We derive analytic
expressions of the entanglement-death time in two special cases: when the
reservoirs for each mode are identical, as well as when a single reservoir acts
on the first mode only. In the latter configuration, we show that all the pure
Gaussian states lose their entanglement at the same time determined solely by
the field-reservoir coupling. Also investigated is the evolution of the
Gaussian quantum discord for the same choices of thermal baths. We notice that
the discord can increase in time above its initial value in a special
situation, namely, when it is defined by local measurements on the attenuated
mode and the input state is mixed. This enhancement of discord is stronger for
zero-temperature reservoirs and increases with the input degree of mixing.
