The rocks prevailing in the territory of the National Park are mainly of alpine age, limestone, marble and shale. There are three basic rock zones namely, the inferior one, which is called Plattenkalk and appears at Cavo Sidero in the form of marble plates, the intermediate, comprising dark red phyllite and shale, called Phyllites-quartzites, and the superior, made up of limestone, dolomite, flysch, sandstone, clay and conglomerate rocks and called Tripolitsa.
In the mountain zone and above other rock layers there are erosion residues in the Magassa rock, comprising mainly white limestone. Over a more limited area, mainly in the northern part, there are more recent post-alpine rocks, the Miocene, Pleiocene and Pleistocene.
Middle Jurassic to Upper Eocene
The Plattenkalk zone, also known as the Mani-Crete zone, is the backbone of Crete, along which all other rock zones of the island are placed. A variety of different geological formations converge at this point, such as white marble, dolomite, shale and others. Sitia region is best represented by typical limestone plates (Plattenkalk).
This is metamorphic limestone (marble), which appears in thin layers, similar to plates. Between them, there are thin, white strips or lenses of white silicon material and sponge remnants, which, in many parts of the island, were used to sharpen metal (grindstone).
These rocks were formed from 140 to 30 million years ago, during the Jurassic period. They are encountered in the North West part of the Geopark, namely the Cavo Sidero promontory, as well as at the territory south of the villages Exo and Mesa Mouliana.
One very special category of that unit are the Kalavros beds, which include mostly schist just before the upper unit of Phyllites – Quartzites.
Phyllites – Quartzites s.l.
Upper Permian to Carnian
The Phyllites-Quartzites zone includes very old metamorphic shale (some of it as old as 300 million years), which was dragged by faults and dropped onto the previous zone. Within these rocks, besides the shale, there are also marble, volcanic rock and Quartzite (metamorphic sand and shingle). Within the Geopark territory, the most characteristic rocks are dark red (purple) phyllites, reddish marble, shale and quartzite, with impressive sites above the village of Karydi and on the coast south of Vai up to Maridatis.
There are also impressive rocks in the Zakros and Karydi areas, the most typical of which are purple phyllites. Due to being subjected to re-heating and high pressure 23 million years ago, when they were found buried 40 km deep near the faults, there are today quartz crystals within these rocks as well as iron ores, such limonite.
Upper triasic to upper cretaceous
The rocks prevailing in the region, however, are of the Tripolitsa zone, covering the Phyllites-Quartzites. Tripoli was formed during Alpine orogeny and then transported to its present site by faults. It makes up two main zones, namely, limestone/dolomite and flysch. Limestone/Dolomite was formed in the Triassic and up to the upper Eocene epochs (i.e. 200-50 million years ago) in the surrounding shallow marine waters. This is why it contains numerous characteristic fossils.
Due to its content (made of carbonated calcium, or magnesium, in the case of dolomite) it has undergone intense karstic erosion and includes almost all karstic geoformations, such as caves and gorges, while it creates the aquifers of the region. At its base the rock becomes thin dolomite and is mixed with clay sediments and shoal. Such rocks are typically seen in the territory around Toplou Monastery, where several folds are created.
Flysch is more recent (around 50 million years) comprising clay, sand, shale and conglomerate.
Typical sites where it is found are around Kato Zakros, Karoubes, Mavros Kambos, Skalia, Agia Eirini and along the Xerokambos-Kato Zakros road.
Middle Jurassic to upper Lutetian
The Magassa zone, corresponding to the Pindus, is encountered in the rest of Crete. It lies over the Tripolitsa zone and contains deep-sea, light-coloured limestone (micro-breccias and oval-shaped limestone), formed around 100 million years ago. Such rock appears within the territory of the Natural Park around Magassa village (Vrysidi), where they take their name from, while there are alsotypical sites along Agia Eirini coast, in the region between Ziros and Sitanos as well as on the Platyvolo Plateau.
Limestone of the Magassa zone lies over Tripolitsa rocks, because it was dropped onto this site by faults; these formations are called nappes and can be found along the Ziros-Xirocambos road and in the area surrounding the village of Magassa.
Miocene Rocks (Skopi Formation)
Lower – middle Tortonion (12-10 million years ago)
The older Miocene rocks are known as Scopi formation and include clastic, shallow-sea, sedimentary rocks, namely fossil-bearing sandstone, micro-breccias and clay formed some 12-10 million years ago.
Within the Natural Park grounds, the most characteristic sites like in its north part, mainly around Toplou Monastery and around the Marvro Mouri Hill, as well as around the area of Skopi.
Miocene Rocks (Kastri and Paleokastro Formations)
10-8.5 million years ago
The next younger rocks were formed 10-8.5 million years ago on dry land and they belong to the Kastri formation. They include layers of reddish conglomerate, sandstone and clay, typically appearing on Kastri Hill, in the district of Chiona and on Bodalaki beach.
The most recent Miocene rocksare those of the Paleokastro formation (7-6 million years old), comprising more lightly coloured white-yellow limestone and marl, which contain numerous coral and clypeaster sea urchin fossils. Typical sites of such limestone lie north of Karoumbes beach, within Kato Zakros gorge and northwest of Toplou Monastery gorge. They also appear at the large neotectonic basin south of Sitia.
Pliocene (5-3 million years)
Pliocene rocks of the National Park appear on the Argilos beach in Xerocambos, while smaller sites are found along the Katsounaki-Kato Zakros footpath. They mainly include white to green marls, which contain fragments of fossilized shells.
It is worth noting that the Argilos beach marls present some particular features, namely their high clay grain content and very dense fissures that create small fragments, easily broken off manually without any mechanical means. This is what has made the beach famous, because visitors break off marl clay-rich fragments to smear their bodies.
Pleistocene (1.5 million – 50.000 years old)
The Pleistocene rocks of the area appear along the coastal zone and they are 1.5 million –50.000 years old). These were formed in the most recent geological periods, usually at sites covered by the sea. They are mainly made up of sandstone and conglomerate with calcite connective matter and ample fragments with fossilized organisms, such as echinoderms, gastropods and bivalves. Among them mammal fossils have been found (hippopotami and deer).
These are mainly encountered in the shores of the park, specifically at Xerocambos, Ambelos, Kato Zakros, the coast of Traostalos and Karoumes Bay. Besides marine Pleistocene sedimentary rocks, in particular on Katsounaki beach, Agia Fotia beach and Tenta Bay, there is a special type of aeolian rocks, the famous aeolian sandstone or aeolianite. This is lithified marine dune sand held together by limestone.
Quaternary sediments include very recent continental clastic sedimentary deposits, products of fluvial deposits, or other erosional deposits in plateaus, valleys, and coastal zones.