Relación de las direcciones de karstificación y del termalismo con la fracturación en las Cordilleras Béticas.

Abstract

Based on the interpretation of aerial photographs (scales between 1:10,000 and 1:35,000) an analysis is made of the various karstic fracture systems within the Betic Cordilleras of Southern Spain. The age of the fractured materials is comprised between the Middle Triassic to the Pliocene, with lithologies that. though predominantly carbonatic, also include celestite, and gypsum-bearing evaporites, Besides their directional frequency, the methodologies employed also allowed an estimate of the length relationships among fracture systems. The resulta so obtained, tested against field observations, indicate that two fracture systems (N 130-160 E and N 5-35 E) are predominant, characterized respective1y by a relatively greater length of its componental fractures and by having a bimodal directional frequency, On a regional scale both systems correlate well with important structural lineaments that appear to have been active either as strike-slip or normal faults. Another fracture system striking roughly N 70-100 E presents comparatively less evidence of karstification, in spite of its considerable tectonic and paleogeographic significance (i. e., it parallels the boundary between internal ad external realms of the cordilleras, the socalled Cádiz-Alicante fracture system), The intersection of these systems (especially those striking N 70-100 E and N 130160 E) appears to be a major control of the location of the main thermal springs , as well as of the intense seismic activity of the area. From a methodological standpoint. the results obtained in this study cover a scale level about which no information was previously available, and confirm existing hypotheses -based on satellite imaginery and microtectonic analysis-s- concerning the occurrence of changes in the orientation of the maximum vector of compressive stress. The strike of the karstification lineaments here signaled coincide with those obtained in analogous studies in the portuguese Algarve region, on the other hand, which suggests that the mesozoic and cainozoic karst systems in the south of the Iberian Peninsula may have had a common evolution.