Considerazioni sulla provenienza delle intercalazioni carbonatiche nella successione terrigena messiniana nella valle dell'Ausente (Appennino centromeridionale)

This work addresses the stratigraphical-scdimcntological analysis of the bioclastc limestonc deposits intercalated in two terrigenous units of Early Messinian age (Unità M.te Bracchi and Fornaci Pontine). These units constitute the middle to upper portion of the Upper Miocene terrigenous succession in the eastem Aurunci rcgion. The limestone deposits of the M. Bracchi Unit represent a channel deposit.s at the base slope enviroment, with gravitional flows coming from North. The limestone deposits of the Fornaci Pontine Unit represent a caothic horizon of the slope enviroment. Petrographically, the bioclastic and intraclastic rocks contain the following biological association: coralline algae, bryozoans, pelecypoda, echinoids and barnacles. The matrix is rich in planktonic foraminifera with subordinate phosphatic, glauconitic and quartz grains. These litho and biofacies association ret1ect foramol type (rodalgal). Two hipoteses about the sourcc area of these deposits are proposed: 1) narrow palaeo-structural high inside the basin or 2) wide elevateci arca lying on the Messinian orogenic front.