MMNP is situated on the oldest rock formation in the country, Macin Mountains, which is a remaining of the Hercinian-Kimeric folding. The significant rocks are: gneiss granites in south and east, crystaline limes in south-east, metamorphic and eruptive rocks in the north, loess deposits on plateaus at little altitudes. The Carapelit structures, also present here, consist of conglomerates, gritstones, detrital deposits. This stripe of softer rocks is bordered by Devonian and Silurian layers consisting mainly of quartzites and resulting in a series of cornets. 

In the Northern Dobrudja there are specific Precambrian, Paleozoic, Mezozoic deposits penetrated by intrusions and extrusions of eruptive rocks to which metamorphic rocks add, too. After these formations were folded in different stages (former Kimmerian, Precambrian and Paleozoic), they were peneplaned. Therefore, at present there can be seen only the remaining of the mountain folding. Older formations from the loess layer formed in Quaternary stage emerge only on restricted portions. From the geological point of view, Northern Dobrudja can be divided in the following zones: Macin unit corresponding to Macin Mountains, Niculitel unit and Tulcea unit. The last two correspond to Tulcea zone.

Măcin unit is formed by a foundation of crystalin schists and massifs of granite rocks also known as pre-Hercinian magmatites, a Paleozoic deposit of carboniferous age represented by Carapelit formation (made of an interbedding of grawacke grit stones and clay slates). The Carapelite formation is penetrated by granite formations to which a post-Hercinian layer adds, too.