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Office:3061B
Derring Hall
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Professor: Virginia Tech, 2008-;
Associate Professor: Virginia Tech, 2005-2008;
Assistant Professor: Virginia Tech, 2003-2005;
Assistant Professor: Tulane University, 2000-2003;
Postdoctoral Fellow: Harvard University, 1998-2000;
Research Assistant: Nanjing Institute of Geology and Paleontology, 1991-1993;
PhD: Harvard University, 1998;
AM: Harvard University, 1996;
MSc: Beijing University, 1991;
BSc: Beijing University, 1988;
GEOS 1014 Earth and Life Through Time
GEOS 5014 Earth System History
GEOS 5984 Current Topics in Geobiology
GEOS 6304 Current Topics in Paleobiology and Sedimentology
Focuses: Precambrian Geobiology; Early Animal History; Proterozoic Algal Fossils; Lagerstätten; Taphonomy;
Other Interests: Carbonates; Isotopes; Fossil Record of Microbes;
The Doushantuo project
Xiao and his colleagues have been focusing on the Ediacaran Doushantuo Formation (ca. 551-635 million years old) in South China. The Doushantuo Formation contains multiple taphonomic windows. Extraordinary fossils such as animal embryos and multicellular algae are preserved in Doushantuo phosphorites and cherts. Macroscopic algal fossils occur in Doushantuo shales. Together these taphonomic windows give a clearer and more complete picture of the Neoproterozoic biosphere and provides insights into preservational biases of the Neoproterozoic fossil record. Xiao and collaborators are also working on geochemical proxies (mainly C and S isotopes) to characterize environmental context of Doushantuo evolution. Reliable reconstruction of the distribution of Ediacaran biodiversity and paleoenvironmental conditions is critical to the understanding of the patterns and interactions between Edicaran environmental and biological evolution.
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cells about 20 micrometer in size |
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Animal embryos (1), multicellular algae (2, note T-shaped cell junctions and small cell size about 20 micrometers), spiny acritarchs (3), and branched tubular fossils (4) preserved in Doushantuo phosphorites.
Click the following links to download animations of Doushantuo embryo fossils based on X-ray tomographic data. Please cite the following references:
Hagadorn, J. W., S. Xiao, P. C. J. Donoghue, S. Bengtson, N. J. Gostling, M. Pawlowska, E. C. Raff, R. A. Raff, F. R. Turner, C. Yin, C. Zhou, X. Yuan, M. B. McFeely, M. Stampanoni, and K. H. Nealson, Cellular and subcellular structure of Neoproterozoic embryos. Science, 314: 291–294.
Four-cell embryo with intracellular structures (.mov format; .avi format)
Two-cell embryo with intracellular structures (.mov format)
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| Spiny acritarchs preserved in Doushantuo cherts. |
Carbonaceous algal fossils (specimen about 5 cm in height) in Doushantuo shales. |
Journal covers featuring our research.
The Quruqtagh Project
The Quruqtagh Group in the Gobi desert of NW China is one of the few Neoproterozoic succession that contain multiple glacial intervals. Xiao and collaborators have been studying the litho- and chemostratigraphy of the Quruqtagh Group in order to clarify the global picture of Neoproterozoic glaciations, their paleoenvironmental impact, and their relationships with biological evolution.
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| Field work in Aksu, Xinjiang. |
Pinkish cap carbonate (left) overlying the dark-colored Tereeken diamictite (right). |
The Early Cambrian Project
Our work on early Cambrin paleontology in South China and Tarim Basin is an effort to understand the diversity of ecological roles of Early Cambrian sponges and acritarchs. Focuses include the Hetang biota in South China and the Yurtus/Xishanblaq Formation in Tarim. The Hetang biota is dominated by large (0.5 - 1 m) articulated sponges but small (<0.5 cm) bilaterians. The Yurtus/Xishanblaq Formation contains abundant small shelly fossils and Micrhystridium-like acritarchs. Paleontological study of the Hetang and Yurtus/Xishanblaq biotas provides fossil evidence to test hypotheses about the ecological and geobiological roles of early Cambrian animals and phytoplankton.
An spiny acritarch from the basal Cambrian Yurtus Formation in Tarim (left, vesilce diameter about 0.01 mm); Reconstruction of a hexactinellid sponge from the Hetang Formation (middle; scale bar = 5 cm); Hetang sponge fossils preserved on bedding surface of black shale (Right).
The Mesoproterozoic-Archean Project
Xiao and collaborators use a variety of tools to characterize the microchemistry and ultratructures of microfossils from Mesoproterozoic and Archean rocks. The goal is to identify biogenic features in these simple microfossils, to constrain the phylogenetic affinities of such ancient microfossils, and to develop proxies for Proterozoic and Archean oceanic and atmospheric chemistry.
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| Outcrop of the Ruyang Group |
Shuiyousphaeridium macroreticulatum (ca. 150 micrometers) | Dictyosphaera delicata (ca. 150 micrometers) |
Collaborators:
Huiming Bao (Louisiana State University
at Baton Rouge);
Gry Barfod
(UC Davis);
Xuelei Chu (Institute of Geology and Geophysics,
Chinese Academy of Sciences);
Whitey Hagadorn (Amherst College);
Ganqing Jiang (UNLV);
Michal Kowalewski (Virginia
Tech);
Alan Jay
Kaufman (University of Maryland);
Andrew H. Knoll
(Harvard University);
Guoxiang Li (Nanjing
Institute of Geology and Paleontology);
Pengju Liu (Chinese Academy of Geological Sciences);
Guy M. Narbonne (Queen's
University);
Ronald L. Parsley
(Tulane University);
Curt Pueschel (Binghamton
University);
Bob Tucker (Washington
University);
Jiasheng Wang (China University of Geosciences)
Leiming Yin (Nanjing
Institute of Geology and Paleontology);
Xunlai Yuan (Nanjing
Institute of Geology and Paleontology);
Chuanming Zhou (Nanjing
Institute of Geology and Paleontology);
and many others;
Sponsors:
National Science Foundation
National Geographic Society
American Chemical Society Petroleum Research Fund
National Natural Science Foundation of China
Chinese Academy of Sciences
Chinese Ministry of Science
and Technology
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