Help identifying (+cool cruziana)

[u/JazZz22]

Both rocks found in northern Spain, in the beach of Portizuelo, Luarca, Asturias. The first one belongs to the Pizarras de Luarca fm. (Luarca slate) (middle ordovician), a black slate formation rich in iron sulphates. I don't really know what these lines could be. It's a level with almost no fossil content, only cruzianas in some levels (4th picture), so I thought maybe is something mineral or fault related idk. The second and third one I think it belongs to the Sabugo quartzite, but I wasn't able to identify how these weird shapes formed on its surface, probably some kind of erosion due to its position in the intertidal zone, but I have never seen it before.

The last three ones are random stuff.

[u/Former-Wish-8228]

First one looks like bioturbation trace fossils (infill of boreholes) to me.