The path that goes up the valley of the Rubió stream on the Puigsoler slope, from the Vallhonesta neighbourhood towards the range of El Ginebral and the pass of Gipó, crosses, a few hundred meters beyond the large farmhouse of Can Forns, two inactive and contiguous quarries: first and below the path the old quarry named Can Forns, and then and above the path the modern one named El Roure. They are absolutely different. The old quarry of Can Forns is relatively small and used artisanal stonemasonry techniques to extract nummulitic biocalcarenite; on the other hand, the modern quarry of El Roure has opened a huge hollow in the mountainside using explosions of dynamite to benefit from some rocks, mostly sandstones. Here we focus on the geology that the old quarry of Can Forns displays.
The old quarry of Can Forns is squared. It has a 3-5 meters height cut displaying the remains of the rock stratum that was exploited, and flat surfaces both at the foot or working base and above. In overall, it is a large rocky step (photo 1). The rock is a biocalcarenite that contains very small nummulites (photo 3). In this rock of calcareous nature and top position, rainwater dissolves the calcium carbonate opening its way through cracks that gradually enlarges, in the process of karstification. The section of the quarry shows the karst, the network of cracks of variable size within this mass of carbonate rock (photo 2). In the cracks, the circulation of water drags and washes away a red, clayey soil to a complete decarbonation despite being contained in a fully calcareous rock.
[photos Florenci Vallès (1st) and Jordi Badia (2nd and 3rd)]