The Devonian is western North Macedonia is also defined by phyllites, together with graphite shale, conglomerate, quartzite and carbonaceous shales, along with marble containing crinoid fossils. Paleozoic formations in different zones indicate that the lower units are most complex in eastern North Macedonia, while the Ordovician and Devonian formations tend to be less numerous in the Vardar Zone and are generally more present in the west. The Kraistides, a volcanic complex spanning into neighboring Bulgaria dominates some parts of the country, with greenschist, metadiabase and spilite in its lower levels, and phyllite schists in its upper levels.