GEOMORFOLOGIA DEL COMPLESSO CARSICO GROTTA DEL MEZZOGIORNO (4MA-NA) -FRASASSI (1MA-AN) CON RIFERIMENTO AI MOTIVI NEOTETTONICI DELL'ANTICLINALE DI MONTE VALMONTAGNANA (APPENNINO MARCHIGIANO)

Abstract

The caves under examination develop from m 100 to 260 above the talweg of Sentina stream that conditioned their genesis. The first tunnels are placed on a EW fracture of jurassic age re­established during the Early and Middle Pleistocene uplifting. They seem to testify subterraneous loss of water from a Paleao Sentina to a Paleo Esino river. Somewhat later the activation of a thick series of fractures and faults displaced this former net of galleries and allowed its progressive piracy towards the Sentina. On these faults, oriented northeastwards and gently obliquely sliping, and on the above mentioned EW fracture develops the second karts floor. The NE faults displacing the former tunnels delimit differenciated uplifting blocks whose moviments lead to the formation of sintec­tonic surimposed karst floors even if formed during the same orizontal enlargernent. The galleries lie at progressive high eleva­tion, getting to the anticline axis, which is oriented in apennine direction (NW-SE) and therefore it has been possible connect the movements belonging to the differentiated uplifting of the an­ticline, which caused some of its actuel morphological and struc­tural asirnmetry. Some of the differentiated upliftings and con­seguently the activation of the NE faults are mindelian and premindelian but rnost of them are certainly mindel-rissian cause the second hypogeal leve!, strongly displaced, drained towards the inside of the 1 st order terraced alluvia attributed to Mindel.