A new stratigraphic framework built on U-Pb single-zircon TIMS ages and implications for the timing of the penultimate icehouse (Parana Basin, Brazil)

作者：Griffis Neil Patrick^*; Mundil Roland; Montanez Isabel Patricia; I**ell John; Fedorchuk Nicholas; Vesely Fernando; Iannuzzi Roberto; Yin Qing Zhu

来源：Geological Society of America Bulletin, 2018, 130(5-6): 848-858.

DOI：10.1130/B31775.1

The timing of the late Paleozoic glaciation and its terminal deglaciation in the Parana Basin, Brazil, is unconstrained and prohibits correlation of the Parana Basin ice record with other high-latitude Gondwanan and low-latitude contemporaneous records. Here, we reexamine the existing U-Pb framework for the Carboniferous-Permian Parana succession through high-precision, single-crystal chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) analysis of individual zircons from tonsteins and subaerial volcanic ash deposits, which overlie sedimentary deposits with glacial indicators. The new ages document two distinct volcanic intervals and define a substantially new and revised chronostratigraphy for postglacial coal-bearing intervals in the southern Parana Basin. The new CA-TIMS ages further indicate that glaciation in south-central Gondwana, long considered to be Early Permian, is entirely Carboniferous in age and that terminal deglaciation in this key west-central Gondwanan basin occurred near the Permian-Carboniferous boundary. Single-crystal U-Pb CA-TIMS ages from the ice-proximal high-latitude basins of southern Africa and Australia are needed to test the synchronicity of late Paleozoic glaciation and deglaciation events throughout Gondwana, with implications for empirical- and model-based paleo-climate reconstructions.

• 出版日期2018-5