Some of the speleothems of the Cova de Can Marçà: stalactites, stalagmites and columns.
The Cova de Can Marçà was discovered by smugglers, who used the cave’s small rooms and galleries to hide their goods. The original entrance was about 10 metres above sea level and due to the low ceilings of these rooms and galleries the smugglers had to crawl into them. To guide themselves they made marks on the walls that are still identifiable today.
The owners of the land began restoration works in 1978 and in 1980 the cave was opened to the public.
The Cova de Can Marçà took shape among fossiliferous limestones from the Lower Cretaceous, structured into thick layers with very occasional intercalations of margo-calcareous soils and marls. The sedimentation of this unit occurred on a shallow platform of clean, oxygenated waters with active production and sedimentation of carbonates, the majority originated from the exoskeletons of the organisms that lived there. This would be a sedimentary environment similar to that of a present-day reef.
These materials were exposed to the air by the compressive tectonic forces which occurred during the Alpine Orogeny, causing the folding of the pre-existing sediments and the appearance of various faults.
General appearance of the Cretaceous limestone unit. In black, some of the well-defined strata, in red the faults and in purple the chaotic appearance towards the south.
The fact that these limestones present deformations and faults has favoured the processes of karstic dissolution. The surface water used the zones of weakness created by the faults (Figure 1) to progressively dissolve the calcium carbonate of the limestones, creating cavities which gradually connected with each other (Figure 2).
As the cavities formed and the ceiling lost its base support, subsidences occurred which enlarged the galleries or formed new rooms (Figure 3).
Associated with the karstic dissolution, carbonate is also deposited, which gives rise to what are known as speleothems.
When the water in the fractures evaporates, the calcium carbonate dissolved in it precipitates and accumulates forming a diversity of structures.
Diagram representing the processes which originated the Cova de Can Marçà.
When the calcium carbonate precipitates forming needles that hang from the ceiling, the speleothems are called stalactites (nº 1 in the photo); when they rise up from the floor of the cavity they are stalagmites (2). When stalactites and stalagmites join together they form columns (3).
Draperies (4) are another type of speleothems that can be found in the Cova de Can Marçà. They are formed by the vertical precipitation of calcium carbonate onto inclined surfaces. Due to irregularities in the rock, the water deviates
when it glides over the inclined surface and it deposits the mineral beside the previous deposit, gradually forming wavelike surfaces.
Types of speleothems that can be found in the Cova de Can Marçà (explained in the text).
When the water loaded with calcium carbonate has accumulated, this mineral precipitates over the edges because this is where the water is shallowest and can evaporate more easily. Small walls are formed surrounding the basin where the water had accumulated, giving rise to what are known as gours or rimstone (5). Gours tend to form groups, giving the sloping zones of the cave the appearance of terraces.
