Geology

            The Piatra Craiului range represents one of the most diverse and fascinating geological records of the Romanian Carpathians. It nearly comprises the full spectrum of sedimentary rocks (carbonates, sandstones, shales, conglomerates, phosphorites and chertstones) which were deposited on an older metamorphic basement mainly during Jurassic and Cretaceous periods, when the limestone in Piatra Craiului rose from the bottom of the sea. According to the French geographer, Emanuel de Martonne, the calcareous ridge of Piatra Craiului, with the elegance of its bold profile, opposes the massive shapes of the Bucegi and the Papusa mountains, constituting a morphological accident in the Southern Carpathians.

 

 

The geological history of the Piatra Craiului mountains started 175 million years ago, when the continental crust started to stretch and break up due to the opening of Tethys ocean (like nowadays in the East African Rift). Huge continental blocks progressively subsided and rotated along major faults. An asymmetrical basin formed slowly in front of the continental margin, which started to gather sediments derived from the up lifted and eroded hinterland chains (Fagaras Mountains). These sediments are mainly comprised of calcareous sandstones and fossiliferous marls. After 10 million years, complex phosphatic elements, unleashed by submarine volcanic eruptions in the deeper part of Tethys ocean, were precipitated on the whole shelf, depositing a very rare rock – phosphorite. Although extremely thin (1 meter), it contains the most comprehensive spectrum of marine fossils in Piatra Craiului mountains. More than 130 different species of ammonites, bivalves and gastropods have been found in this interval.

During Upper Jurassic (160 million years ago) the basin subsidence accelerated and the water depth increased to several hundreds of meters. At the same time, further off the shore, in the area of the actual Bucegi mountains, coral reefs developed on a shallow platform. However, these reefs were continuously eroded by storms and deposited as detritus into the Piatra Craiului basin. 

            They accumulated as massive carbonate breccias at the bottom of the basin, filling it up and thus, giving rise to a huge carbonate platform. Out of the 1500 meters thick carbonate stack of the Piatra Craiului ridge, the lower 500 meters are made from these hard limestone breccias, the rest being composed of white platform limestone. The lithological boundary between the two types of limestone is clearly visible along the western slope – Braul de Mijloc. 

             The platform limestone, found in the upper part of the massif, were precipitated mainly by seaweed, which inhabited a vast, shallow lagoon. This limestone occurs in the upper part of the Piatra Craiului ridge and one of its characteristic features is the well preserved stratification (e.g. the Timbale Peaks or the Big Scree Wall). 

During the Cretaceous period (130 million years ago) tectonic movements started to lift the continental margin and the closing of the ocean began. The carbonate platform was faulted and folded and partly emerged. Extensive erosion of continental margin and of the hinterland took place and a tremendous amount of debris accumulated in the remaining parts of the basin as conglomerates. Huge blocks of the former platform slipped and were amalgamated and deposited within these conglomerates. Such blocks are visible nowadays in the area of Magura village. At the end of the Cretaceous period the whole region was emerged and marine sedimentation ceased. Tectonic movements continued and the actual relief was formed quite recently. A beautiful example is the up lift which occurred 5 million years ago in the area, forcing rivers to cut their way through hard limestone, thus creating Prapastiile Zarnestilor and Dambovicioara Gorges.