rare rapids
Primal's Thorny Acacia trees generate coarse dirt underneath them during generation and when grown from a sapling. When NML is installed, some logs - usually towards the top when the tree is branching out - are replaced with coarse dirt. I have a feeling this is a similar issue to mangrove tree roots generating mud that happened a while back.
Tested with the most recent versions of both mods on a fresh instance, and the issue does not occur when only Primal is installed.
(Primal on Modrinth: https://modrinth.com/mod/mod-primal)
deep verge
elfin wren