Stratigraphy and Geochemical Characterization of the Middle Triassic - Carnian Sequence of the Lumiei Valley (Carnia, Northeastern Italy)

摘要

Stratigraphy of carbonate and terrigenous beds of the Anisian, Ladinian and Carnian of the Lumiei Valley (Middle-Western sector of Carnia, NE Italy) is updated and referred to the new chronological scale of Triassic. Western Carnian Alps were emerged in Early Anisian time. The sea transgressed southward and the region was covered by a thick sequence of lagoonal, clastic, and pelagic sediments. The sequence is thicker in this area, where a system of synsedimentary faults increased the subsidence. Tectonic activity increased during Middle(?) Anisian; this area turned into a topographic and structural high, divided by synsedimentary faults from neighbouring open-marine areas that received large amounts of terrigenous sediments. The latest Anisian and the Ladinian are characterized by a general progradation of the platform facies. Basin areas with pelagic and volcanic sediments were mostly developed in this area and towards the Carnian-Julian Alps. In the Late Ladinian a local resuming of volcanism is present in the transgression marked by the Acquatona Formation. The topmost part of the Ladinian is characterized by the general and wide diffusion of the inner platform, mostly with peritidal facies. At the Ladinian-Carnian boundary, tensional tectonics caused the breaking up of the Schlern platform and increased the subsidence. In the Early-Middle Carnian, this area is dominated by a marine transgression with marly limestone, pelagic, and terrigenous sediments. Moreover, major, minor and trace elements were determined. Statistical multivariate analysis methods were applied to experimental geochemical data to study the stratigraphic sequence. The purpose of this paper was to verify the capacity of these methods to describe the different lithologies of the sequence through its geochemical analysis. A multivariate statistical analysis based on geochemical parameters identifies distinct groups of sediments corresponding to lithological intervals of the examined sequence. In this way a good correspondence between geochemical groups and the lithologies was established.