Events Calendar
Unless noted, all listed events are open to the general public. The following events occur during the academic year.
Wednesday Seminar
Wednesday, May 21 at 12-1 PM
1348 Earth and Physical Sciences
Speaker: Francis Alexander Macdonald, UC Berkeley
Title: "Stratigraphic and geochemical tests of the Snowball Earth hypothesis"
Abstract: Twice during the Cryogenian Period (720-635 Ma), ice-sheets extended to equatorial latitudes for millions of years, during the Sturtian and Marinoan glaciations. These climate extremes have been interpreted to record the Snowball climate state, in which all of the Earth’s oceans were covered with ice. Geochronology has provided a first order test of the Cryogenian Snowball Earth hypothesis demonstrating that both the Sturtian (717 to 661 Ma) and Marinoan (639 to 635 Ma) glaciations lasted for millions of years, and each had globally synchronous terminations. However, three major challenges to the Snowball Earth hypothesis remain: 1) Some Cryogenian successions preserve multiple ice advances and retreats associated with sedimentary evidence for open water; 2) Deep ocean chemistry should have evolved towards mantle values through hydrothermal exchange at mid-ocean ridges, but cap carbonates that overlie the Cryogenian glacial deposits have yielded radiogenic strontium isotope (87Sr/86Sr) values similar to seawater values prior to glaciation; and 3) Photosynthetic eukaryotes survived and diversified through the glaciations. In this talk I will address these challenges with stratigraphic, paleomagnetic, and geochemical data from the Dhofar region of Oman.
Friday Lunch Talk
Friday, May 23 at 12-1 PM
1348 Earth and Physical Sciences
“Exit Talk: Active Faulting at Lassen Volcanic National Park”
Speaker: Evelyn Usher
Twice during the Cryogenian Period (720-635 Ma), ice-sheets extended to equatorial latitudes for millions of years, during the Sturtian and Marinoan glaciations. These climate extremes have been interpreted to record the Snowball climate state, in which all of the Earth’s oceans were covered with ice. Geochronology has provided a first order test of the Cryogenian Snowball Earth hypothesis demonstrating that both the Sturtian (717 to 661 Ma) and Marinoan (639 to 635 Ma) glaciations lasted for millions of years, and each had globally synchronous terminations. However, three major challenges to the Snowball Earth hypothesis remain: 1) Some Cryogenian successions preserve multiple ice advances and retreats associated with sedimentary evidence for open water; 2) Deep ocean chemistry should have evolved towards mantle values through hydrothermal exchange at mid-ocean ridges, but cap carbonates that overlie the Cryogenian glacial deposits have yielded radiogenic strontium isotope (87Sr/86Sr) values similar to seawater values prior to glaciation; and 3) Photosynthetic eukaryotes survived and diversified through the glaciations. In this talk I will address these challenges with stratigraphic, paleomagnetic, and geochemical data from the Dhofar region of Oman.
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