The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale

作者：Peter Brack, Hans Rieber, Alda Nicora, Roland Mundil · 发表于：Episodes · 年份：2005 · DOI：10.18814/epiiugs/2005/v28i4/001 · 被引用次数：176 · 研究领域：Evolution and Paleontology Studies、Paleontology and Stratigraphy of Fossils、Paleontology and Evolutionary Biology

The Global boundary Stratotype Section and Point (GSSP) for the base of the Ladinian Stage (Middle Triassic) is defined in the Caffaro river bed (45°49'09.5''N,10°28'15.5''E),south of the village of Bagolino (Province of Brescia, northern Italy), at the base of a 15-20-cm-thick limestone bed overlying a distinct groove ("Chiesense groove") of limestone nodules in a shaly matrix, located about 5 m above the base of the Buchenstein Formation.The lower surface of the thick limestone bed has the lowest occurrence of the ammonoid Eoprotrachyceras curionii (base of the E. curionii Zone; onset of the Trachyceratidae ammonoid family).Secondary global markers in the uppermost Anisian include the lowest occurrence of conodont Neogondolella praehungarica and a brief normal-polarity magnetic zone recognized in closely correlated sections including the principal auxiliary section at Seceda in the Dolomites.The GSSP-level is bracketed by U-Pb single zircon age data from volcaniclastic horizons, indicating a boundary age of ca 241 Ma.