  We consider cycles on a 3-dimensional Shimura varieties attached to a unitary
group, defined over extensions of a CM field $E$, which appear in the context
of the conjectures of Gan, Gross, and Prasad \cite{gan-gross-prasad}. We
establish a vertical distribution relation for these cycles over an
anticyclotomic extension of $E$, complementing the horizontal distribution
relation of \cite{jetchev:unitary}, and use this to define a family of
norm-compatible cycles over these fields, thus obtaining a universal norm
construction similar to the Heegner $\Lambda$-module constructed from Heegner
points.
