A MIDDLE PERMIAN (ROADIAN) LUNGFISH AESTIVATION BURROW FROM THE RIO DO RASTO FORMATION (PARANA BASIN, BRAZIL) AND ASSOCIATED U-Pb DATING

作者：Francischini, Heitor^*; Dentzien-Dias, Paula; Guerra-Sommer, Margot; Menegat, Rualdo; Schneider Santos, Joao Orestes; Manfroi, Joseline; Schultz, Cesar Leandro

来源：Palaios, 2018, 33(2): 69-84.

DOI：10.2110/palo.2017.050

• PAWNEE CREEK FORMATION
• LARGE TETRAPOD BURROWS
• UPPER TRIASSIC CHINLE
• GRANDE-DO-SUL
• WILLWOOD FORMATION
• SOUTH-AMERICA
• BIGHORN BASIN
• DOLORES FORMATIONS
• GREENHOUSE CRISES
• CRAYFISH BURROWS

The Permian Rio do Rasto Formation (Parana Basin) crops out in southern Brazil and was deposited under fluvio-lacustrine settings. A singular outcrop located in the Acegua municipality (Rio Grande do Sul State) represents a sequence of three distinct levels of paleosols in which rhizoliths and a single vertebrate burrow were recovered. The latter has a sub-vertical orientation, a slightly curved shape and a gross morphology and simple architecture that are consistent with aestivation burrows produced by lungfishes. The occurrence of this structure, in association with the features of the paleosols, indicates a seasonal climate with drought events. Additionally, a tonstein layer is interbedded in the paleosol sequence, indicating the influence of volcanic ash falls in the paleoenvironment. Zircons were collected from this level and dated using U-Pb techniques and the obtained age is 270.61 + 1.76/-3.27 Ma (Roadian). The paleoenvironmental context of this outcrop is in accordance with a dry, seasonal climate of southwestern Pangaea during the early Guadalupian.

• 出版日期2018-2