GEOLOGY AND KARSTIFICATION

The cave of Sant’Angelo at Santeramo is located, on a regional scale, in an area (platform) whose origin occurred in the marine environment following the deposition of carbonate material (CaCO3) derived mainly from the accumulation of the remains of organisms with a calcareous skeleton or from the precipitation of carbonate by the activity of living organisms (biogenic nature).
Locally, a portion (sub-region) of this platform is identified with the term ‘Murge’, a karstic plateau, i.e. affected by forms generated by the flow of water both on the surface and underground (karstification) and originating from displacements and deformations (tectonics), which began in the Upper Cretaceous (geological epoch between 100.5-66 million years ago). The carbonate material of the Murge platform is subdivided by the times in which it was deposited and subsequently lithified into two rock bodies (formations) called: the more ancient Bari Limestone (Turonian-Barremian epoch) and the more recent Altamura Limestone (Senonian epoch). These formations present fractures, ‘red earth’ levels and karst forms, with very fine-grained (micritic) or granular limestone and the remains of organisms (fossils).
The area in which the cave is located has a hilly geomorphology with an average altitude of 483 metres above sea level. Here, tectonics has favoured the formation of an upward concave fold (syncline), developing in a NW-SE direction and fractures along a plane (faults) in a WE and NW-SE direction, creating, in the limestone rock mass, also due to its water solubility, ideal conditions for the development of intense karst phenomena that have generated cavities and preferential water flow routes (sinkholes). The permeability of water in the rock mass is therefore due to fracturing and karstification, with its accumulation in deep, multi-level water tables.
Superficial (epigeal) karstification, also favoured by the presence of faults, has given rise to a fluvial karst network (hydrography) devoid of outflows for a good part of the year (ephemeral), due both to the scarcity of rainfall and to the permeability characteristics of the rocky substratum, as well as to other karst forms such as sinkholes.

RUPESTRIAN FORMS BETWEEN APULIA AND MATERA

The geology of the terrain changes on the edge of the Murge towards the Matine plain, where the emergence of the less tenacious calcarenitic bank has made possible the excavation of hypogean environments and settlements, similar to the more evident manifestations of rock formations that characterise Matera and the ravines of the Taranto Ionic arch. Here, churches, houses, oil mills, trappeti, stables, workplaces, tombs, have given shape to entire villages generally along the banks of blades and ravines.

THE CAVE OF SANT’ANGELO

Caves have always struck man’s imagination because of their symbolic value at the origin of numerous cults, myths and legends.
Caves are the oldest sanctuaries of mankind.
In the medieval collective imagination, the darkness of the cave and the inaccessibility of the site created an atmosphere of mystery, of impenetrability, of limitation, as well as physical, psychological and moral.
The cave of Sant’Angelo is a form of underground karstification (hypogeum), not very deep from ground level, which affected the Altamura limestone of the Murge.
To simplify the description, we can subdivide the cave into a main corridor that descends westwards from the entrance into the deepest area; from this corridor three other corridors branch off, almost orthogonally: the first starts from the niche carved into the rock and after about nine metres curves to the right, joining the parallel corridor, while to the east it loses itself in a secondary branch.
The second corridor, parallel to the first, ends at the pond.
Finally, the third innermost one runs parallel to the previous one from which it is separated by a stalagmite barrier.

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