STRATIGRAPHY OF RHAETIAN TO LOWER SINEMURIAN CARBONATE PLATFORMS IN WESTERN LOMBARDY (SOUTHERN ALPS, ITALY): PALEOGEOGRAPHIC IMPLICATIONS

摘要

A stratigraphical revision of the Upper Triassic-Lowcr Jurassic succession of the western Southern Alps (Varese area) leads to the introduction of one new lithostratigraphical unit: the ?upper Het-tangian-lower Sinemurian Alpe Perino Limestone and the recognition, also in the western Lorabardy, of the Rhaetian Zu Limestone, consisting of subtidal cycles, with inner platform facies at the base (Campo dei Fiori Dolomite). These formations represent lagoonal-peritidal to sub-tidal carbonate depositional systems. A locally angular unconformity between the Rhaetian (or the lower Hettangian) and the upper Hettan-gian-Sinemurian formations, characterised by 'terra rossa' paleosols and pedogenetic carbonate breccias, can be correlated through all of the investigated profiles.