Catalonia's Geological Formation: A Deep Dive into its Origins

Catalonia's Geological Formation: Paleozoic Era

During the Paleozoic Era, the area that would become Catalonia was part of a large oceanic basin where argillaceous materials were deposited. These materials, subjected to intense pressure, metamorphosed over millions of years into gneiss, schists, and slates, which now outcrop in the coastal mountains and the Pyrenees Axial Zone.

The Ebro Massif occupies much of the central depression. The Hercynian folding gave rise to the Catalano-Balearic massif, which joined the Ebro Massif, forming a gulf open to the southwest.

Mesozoic Era

During the Mesozoic Era, the sea again invaded most of the land, a condition that persisted until the Cenozoic Era. This period saw the deposition of calcareous materials in tranquil marine environments.

Cenozoic Era and the Rise of the Pyrenees

At the beginning of the Cenozoic Era (Tertiary Period), geographical conditions were similar to those of the Mesozoic Era. However, the motion of the Eurasian and African plates, in contact here, began to gently uplift the region, leading to the formation of mountain ranges. The folding of the Pyrenees is a result of the Alpine Orogeny.

This uplift pushed the sea southwest, covering much of the Ebro basin, which had previously been alternately submerged and emerged, separating the Pyrenees from the Mediterranean basin. This period marked the beginning of the deposition of materials that would form the Central Depression.

Near the coastline, powerful conglomerates accumulated where rivers from the Pyrenees and the Catalano-Balearic Massif emptied into the sea (e.g., the conglomerates of Montserrat, Sant Llorenç de Munt, and Montsant). Inland, sand and clay were deposited, forming sandstone, marl, and marly limestone, gradually filling the center of the Central Depression. Thick limestone deposits accumulated along the coast.

Later, this gulf became a lake with limited communication with the open sea. Intense evaporation led to the deposition of vast saline deposits (e.g., Suria, Cardona).

Towards the second half of the Tertiary Period, the Catalano-Balearic massif largely disappeared, remaining only as a narrow strip of land. Pre-formed depressions formed the coastlines of Cerdanya, the Empordà, and other areas.

Towards the end of the Tertiary, the final stages of the Alpine Orogeny slightly modified the layout of the interior materials in the basins of Cerdanya and the central depression. In the Empordà and Olot, spectacular volcanic activity continued into the Quaternary Period.