In Civilization 6, do rivers "block" adjacency of districts? Put another way, are two tiles with a river running between them "adjacent" for the purposes of district bonuses and placement restrictions?
The immediate context is that I think I should be able to build the Great Library on a tile across a river from my campus (pictured below), but the wonder does not appear for building. More remotely, I'd like to build a triangle or diamond of districts to maximize the adjacency bonus, and I want to know if a river running through will counteract that.
I've looked in the Civilopedia and on the various Civ6 wikis but haven't found a true definition of adjacency and particularly how rivers affect it.