Indiana University Bloomington

Colloquia: Spring 2015

January 12: First day of term (no seminar)

January 19: MLK Day (no classes, no seminar)

January 26: Shuhai Xiao, Virginia Tech. Title: In the Wave of a Cryogenian glaciation and on the Eve of the Cambrian Explosion: Biological Evolution in the Ediacaran Period

Abstract: The evolutionary fuse of the Cambrian explosion is probably buried in the Ediacaran Period. In the past decade, significant progress has been made in Ediacaran paleobiology and geobiology to allow a better understanding of the interactions between environmental and biological evolution across the Ediacaran-Cambrian transition. With integrative paleobiological, stratigraphic, sedimentological and geochemical data, we can now establish a more robust chronostratigraphic framework and environmental context to better understand what happened on the eve of the Cambrian explosion. The discovery of new fossils allows us to have a more complete understanding of Ediacaran biodiversity, paleoecology, and evolutionary dynamics. The calibration and application of novel geochemical proxies gives us new tools to reconstruct paleoenvironmental conditions in the Ediacaran Period. In this talk, I will focus on possible animal fossils in the Ediacaran Period, and will discuss the potential roles of oxygenation and ecological feedbacks in early animal evolution.

February 2: Ariel Anbar, Arizona State University. Title: TBA

Patterson

February 9: Kay Behrensmeyer, Smithsonian Institution. Title: Did Environmental Change Control Human Evolution in Africa

Abstract:In spite of many decades of energetic research and debate about this issue, it is not yet resolved. There is little doubt that environmental change must have played SOME role in shaping human evolution, as it has for most of Earth’s organisms over geological time. This talk is aimed at a balanced consideration of different biological and physical processes, including environmental change, and how they could have affected the evolution of our ancestors. The audience will be invited to think about these processes as possible "controls" in light of the many kinds of evidence that relate to human evolution in Africa, including associated faunas, paleoenvironments, stable isotopes, climate records in drill cores, and patterns contained in the hominid fossil and archeological record itself.

February 16: Frank Ettensohn, Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506. Title: Large-Scale Tectonic and Structural Controls on Ordovician Black-Shale Distribution (Utica and Martinsburg) during the Taconian Orogeny, Northern Appalachian Basin, U.S.A.

Abstract: In the Appalachian Basin, black shales are major parts of most flexural, foreland-basin sequences and reflect the timing of major loading-related, foreland subsidence. Moreover, because of their distinctive character in the surface and subsurface, mapping their distribution can help track the progression of orogeny in space and time. In the U. S. Appalachian area, the distribution of Middle to Upper Ordovician black shales suggests that the Taconian Orogeny proceeded in a diachronous fashion from south to north along the eastern Laurentian margin, and that tectophases were mediated by convergence at successive continental promontories. In the Late Ordovician (late Sandbian–Hirnantian) Taconic tectophase, changes in the distribution of the Martinsburg and Utica black shales support a reversal of subduction polarity that effected the reactivation of basement structures and basin migration sufficient to yoke Appalachian foreland basin with adjacent intracratonic basins. Shale distribution suggests that early Chatfieldian (late Sandbian–early Katian), east-verging subduction early in the tectophase generated a cratonic extensional regime that resulted in a relatively narrow foreland basin along reactivated Iapetan basement structures. Abruptly, however, in late Chatfieldian–early Edenian (early Katian) time, subduction vergence apparently changed to the west, generating a regionally compressional regime that was accompanied by subsidence and change in regional dip, such that black shales and an underlying unconformity migrated westwardly. By Maysvillian (mid-Katian) time, the distribution of Utica and Utica-equivalent black shales show that the Appalachian and Michigan basins merged into one large, fully yoked basin. The coincidence of changes in basin shape and migration with the shift in subduction polarity suggests a causal relationship. The approximate time of polarity change is well-known from other sources, but is also well-constrained by the biostratigraphic ages of and changes in the distribution of the effected black shales.

February 23: Jim Best, University of Illinois. Title: TBA

March 2: Ralph Milliken, Brown University. Title: TBA

March 9: Bob Hazen, Carnegie Institute. Title: TBA

March 23: Steve Bell, IU Biology. Title: TBA

March 30: Julie Elliott, Purdue University. Title: TBA

April 6: Berry Lyons, The Ohio State University. Title: TBA

April 13: (open)

April 20: Gordon Grant, USDA/Oregon State University. Title: TBA

April 27: Tori Hoehler, NASA Ames. Title: TBA