[1] San Diego State Univ, Geol Sci, San Diego, CA 92182 USA
[2] Univ Barcelona, Dinam Terra & Ocea, Barcelona, Spain
[3] Berkeley Geochronol Ctr, 2455 Ridge Rd, Berkeley, CA 94709 USA
[4] Czech Acad Sci, Inst Rock Struct & Mech, V Holesovickach 41, Prague 18209, Czech Republic
[5] Johannes Gutenberg Univ Mainz, Inst Geosci, D-55099 Mainz, Germany