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A Mineralized Alga and Acritarch Dominated Microbiota from the Tully Formation (Givetian) of Pennsylvania, USA

1
Department of Earth and Environmental Sciences, Brooklyn College, Brooklyn, NY 11210, USA
2
PhD Programs in Earth and Environmental Science and Biology, City University of New York, Graduate Center, New York, NY 10016, USA
3
Department of Biology, College of Staten Island, Staten Island, NY 10314, USA
4
Department of Environmental Sciences, William Paterson University, Wayne, NJ 07470, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Olaf Lenz and Jesus Martinez-Frias
Geosciences 2016, 6(4), 57; https://doi.org/10.3390/geosciences6040057
Received: 12 September 2016 / Revised: 9 December 2016 / Accepted: 13 December 2016 / Published: 19 December 2016
Sphaeromorphic algal cysts, most probably of the prasinophyte Tasmanites, and acanthomorphic acritarch vesicles, most probably Solisphaeridium, occur in a single 20 cm thick bed of micritic limestone in the lower part of the Middle Devonian (Givetian) Tully Formation near Lock Haven, Pennsylvania. Specimens are composed of authigenic calcite and pyrite crystals about 5–10 µm in length. Some specimens are completely calcitic; some contain both pyrite and calcite; and many are composed totally of pyrite. The microfossils are about 80 to 150 µm in diameter. Many show signs of originally containing a flexible wall composed of at least two layers. Some appear to have been enclosed in a mucilaginous sheath or membrane when alive. The acanthomorphic forms have spines that are up to 20 µm in length, expand toward the base, and are circular in cross-section. The microflora occurs with microscopic molluscs, dacryoconarids, the enigmatic Jinonicella, and the oldest zooecia of ctenostome bryozoans known from North America. The microalgal horizon lacks macrofossils although small burrows are present. Microalgae and acritarchs have been preserved via a complex preservational process involving rapid, bacterially-mediated post-mortem mineralization of dead cells. The microfossil horizon, and possibly much of the Tully Formation at Lock Haven with similar lithology, formed in a relatively deep, off-shore basin with reduced oxygen availability in the substrate. View Full-Text
Keywords: microalgae; acritarchs; Jinonicella; ctenostome zooecia; Tully Formation; Givetian; Pennsylvania microalgae; acritarchs; Jinonicella; ctenostome zooecia; Tully Formation; Givetian; Pennsylvania
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Chamberlain, J.A.; Chamberlain, R.B.; Brown, J.O. A Mineralized Alga and Acritarch Dominated Microbiota from the Tully Formation (Givetian) of Pennsylvania, USA. Geosciences 2016, 6, 57.

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