  In relation of observable and quantum state, the entity $I_C$ from previous
work quantifies simultaneously coherence, incompatibility and quantumness. In
this article its application to quantum correlations in bipartite states is
studied. It is shown that Zurek's quantum discord can always be expressed as
excess coherence information (global minus local). Strong and weak zero-discord
cases are distinguished and investigated in terms of necessary and sufficient
and sufficient conditions respectively. A unique string of relevant subsystem
observables, each a function of the next, for "interrogating" the global state
about the state of the opposite subsystem is derived with detailed entropy and
information gain discussion. The apparent disappearance of discord in
measurement is investigated, and it is shown that it is actually shifted from
between subsystems 1 and 2 to between subsystems 1 and $(2+3)$, where 3 is the
measuring instrument. Finally, it is shown that the global coherence
information $I_C(A_2,\rho_{12})$ is shifted into the global coherence
information $I_C(A_2,\rho_{123}^f)$ in the final state $\rho_{123}^f$ of the
measurement interaction.
