Exhumed fault-bounded Alpine blocks along the Periadriatic lineament: the Eder unit (Carnic Alps, Austria)

• Published in: Geologische Rundschau Vol. 86; no. 3; pp. 612 - 626
• Main Authors: Läufer, A. L., Frisch, W., Steinitz, G., Loeschke, J.
• Format: Journal Article
• Language: English
• Published: Berlin Springer Nature B.V 1997
• Subjects: Geology; Geophysics; Illite; Metamorphism; Miocene; Oligocene; Paleozoic; Plate tectonics
• ISSN: 0016-7835; 1437-3254; 1432-1149; 1437-3262
• DOI: 10.1007/s005310050167

The Eder unit in the Carnic Alps, which is situated immediately south of the Periadriatic lineament (PL), represents a fault-bounded block consisting of a low-grade (up to 400°C, indicated by epizonal illite "crystallinity" values, recrystallized quartz, and non-recrystallized white mica) metamorphic Paleozoic metasedimentary sequence. Until now, it has been assumed to represent a separate Variscan nappe. The rocks of the Eder unit show a strong E- to W-oriented stretching lineation on steep foliation planes (D^sub 1^) subparallel to the PL. D^sub 1^ structures originated near the temperature peak of metamorphism, and shear sense indicators show dextral ductile shear parallel to the PL. Tight mesoscale D^sub 2^ folds formed on the cooling path. K-Ar and Ar-Ar ages from newly formed white mica cluster around 32-28 and 18-13 Ma and suggest a two-stage Tertiary history of the Eder unit. We interpret the Eder unit as a fault-bounded block formed during Oligocene large-scale dextral shearing along the PL (near T^sub max^) and exhumed in mid-Miocene times during another phase of activity along the PL. Its nature as a separate Variscan nappe is questioned.[PUBLICATION ABSTRACT]