Polyphase metamorphism in the eastern Carnic Alps (N Italy–S Austria): clay minerals and conodont Colour Alteration Index evidence

Abstract

Thermal evolution of the Palaeozoic-Triassic sequences of the Carnic Alps has been characterized by b cell dimension and Kübler Index (illite ''crystallinity'') of K-white micas (KI), Á rkai Index (AI) of chlorites, clay mineral assemblages and conodont Colour Alteration Index (CAI). Data indicate at least two metamorphic events, Variscan and Alpine. In the older event high anchizonal conditions predominated although epizonal conditions were reached over wide areas. It was characterized by lowintermediate pressure facies. The thermal peak was mainly due to an extensional regime during the Bashkirian. A younger thermal overprint generated by Alpine orogeny was of lower grade, reaching high diagenetic-anchizonal conditions characterized by high-pressure facies. Inverted metamorphic patterns are associated with middle to late Miocene thrusting. Hydrothermal alteration in the northern part of the region can be linked with emplacement of Oligocene plutons and high heat flow along the Periadratic lineament.

Tectonothermal evolution of a foreland fold and thrust belt: the Cantabrian Zone (Iberian Variscan belt, NW Spain)

“…The different kinetics of the illitization and the carbonization processes, the former being less sensitive to the time spent at a certain temperature (Hillier et al. , 1995; Brime et al. , 2001, 2003, 2007; Arkai et al.…”

Lower Lochkovian (Lower Devonian) conodonts from Cellon section (Carnic Alps, Austria)

“…This sequence was affected by the Variscan orogeny during the late Bashkirian and early Moscovian (Schönlaub 1980, Venturini 1990, Schönlaub & Forke 2007 and by extensional as well as compressional and transpressional Alpine phases (Venturini 1990, Läufer 1996, which formed a fold and thrust belt. Despite the severe deformation, the succession is mostly non-metamorphic (Brime et al 2008).…”

Insight into the development of a carbonate platform through a multi-disciplinary approach: a case study from the Upper Devonian slope deposits of Mount Freikofel (Carnic Alps, Austria/Italy)

“…Both orogenies resulted in the formation of several thrust sheets, imbricate nappe systems, and dislocations. The Variscan orogeny is interpreted as formed at considerable crustal depth, which leads to more ductile deformations, including recumbent folding (Venturini 1990;Brime et al 2008). The resultant structural setting has been sketched by Läufer et al (2001) who defined four major tectonic units (Fig.…”

“…According to Austrian authors (Piller et al 2004), a summary of the Devonian stratigraphy of the Cellon-Kellerwand Nappe with the location of the Freikofel section is (Piller et al 2004). Modifications are made for the Freikofel Limestone according to its age and relation with the cellon limestone (red dotted line) based on the age range mentioned in Brime et al (2008), on the geological map of Venturini et al (2009), and the new conodont data obtained for this study Int J Earth Sci (Geol Rundsch) illustrated in the Fig. 3.…”