Showing papers by "Joan J. Fornós published in 1995"

Litologia i tectònica del carst de Mallorca: lithology and tectonics of the majorcan karst

Abstract: EnglishThe lithology and structural setting of the rocks which form the island of Mallorca are magnificent bases on which karstic phenomena develop. Almost every geological period is continually represented here, from the Carboniferous to the Pleistocene (only part of the Upper Cretaceous and Lower Paleogene being absent). The approximate thickness of the stratigraphic sequence is 3,000 m in which carbonate deposits (not only limestones but also dolomites) constitute the most hportant lithologies. The main structure consists of thrust sheets imbricated in a NW transport direction. Such deformation tookplace during the alpine orogenia and led to SE declivities showing smoother slopes, which present today a more ancient modelling; whereas the NW slopes are steeper and their relief is younger. Furthermore, the existence of impermeable materials from the Keuper at the base of the thrust sheets, added to the overlapping setting thrusts, cause permeable zones (dolomites and limestones from the Rhaetian and Lias) to remain isolated by areas of impermeable material. catalaLa litologia i disposicio estructural de les roques que conformen I'illa de Mallorca son una magnifica base per al desenvolupament dels fenomens de tipus carstic. A Mallorca hi son representats practicament sense interrupcio materials des del Carbonifer fins al Pleistoce (hi manca part del Cretaci superior i Paleogen inferior). La serie te una potencia aproximada de 3.000 m, dominant ampliament, adhuc els detritics, els diposits de tipus carbonatat, tant calcaries com dolomies, que son els que formen els relleus mes importants de I'illa. L'estructuracio en forma d'escates encavalcants dirigides cap al NW que va tenir lloc durant I'orogenia alpina, va donar com a resultat uns vessants SE amb pendents mes suaus, els quals ja presenten una certa maduresa en el seu modelatge, mentre que els vessants NW presenten pendents mes forts i un relleu juvenil. A mes, el fet que a la base de les Iamines encavalcants s'hi trobin els materials impermeables del Keuper, juntament amb la disposicio imbricada dels encavalcaments, suposa I'existencia de zones permeables (dolomies i calcaries del Retia i Lias) aillades per arees de materials impermeables.