Fall 2013 Colloquia

August 26: No colloquium, 1st day of classes

September 2: Labor Day, no classes

September 9: Ania Szynkiewicz, University of Tennessee Knoxville. Title: Sulfur cycle on Mars from the perspective of a terrestrial geologist.

Abstract: One of the prominent geochemical features on Mars related to past water activity is the widespread occurrence of sulfate-bearing minerals on its surface. The Mg-Ca-Na-Fe sulfate minerals have been identified by rovers and orbital spectrometers in various locations on Mars. These sulfates exhibit different depositional environments including a variety of aqueous, sedimentary and eolian processes but there is also evidence for direct volcanic deposition. Generally, the origin of sulfate minerals on Mars is poorly understood and many competing hypotheses exist in the literature.

During my talk I will present terrestrial geochemical data describing factors controlling sulfur cycle in arid and polar environments on Earth. I will discuss terrestrial analogs from the Rio Grande rift (New Mexico) and Svalbard, and show how they can be used to understand the distribution of sulfate minerals on Mars.

September 16: David Bish, Professor of Mineralogy, Indiana University. Title: The Mars Science Laboratory Experience

ABSTRACT: Mars Science Laboratory (MSL), one of the most ambitious planetary missions ever launched, began its journey to Mars in November, 2011, and landed in Gale crater on the night of 5 August, 2012. MSL carries ten instruments, including a variety of cameras along with radiation, weather, and chemistry analyzers. The rover also includes a device for analyzing the chemistry of gases in the Mars atmosphere and in soils and rocks (the SAM instrument) and the CheMin instrument for detecting the minerals in soils and rocks using X-ray diffraction (XRD). XRD is well established on Earth using much larger laboratory instruments and it can provide more accurate identifications of minerals than any method previously used on the Red Planet. The MSL experience involved working on Mars time with a 24 hour, 39 minute solar day (so-called sol). Thus, if you went to work at 0800 today, you would go to work at almost 2200 in three weeks. Our work with the rover involved sending commands to the rover (˜14 minutes from Earth to Mars) and receiving data from the rover, every day. The first photos from MSL showed a variety of volcanic rocks along with what appear to be sedimentary rocks that support the existence of flowing water in the past. The CheMin instrument first analyzed a sample of martian soil from a dune and found that it is very similar to soils on the flanks of Mauna Kea volcano in Hawaii. Unlike some several-billion-year-old conglomerates that Curiosity investigated, which are consistent with flowing water, the soil that CheMin analyzed is representative of more modern processes on Mars. Subsequent CheMin analyses of drilled rocks revealed the presence of phyllosilicates, which are consistent with formation in water. To date, the materials analyzed by Curiosity support initial ideas that the rocks in Gale Crater may record a transition through time from a wet to dry environment. The ancient rocks, such as the conglomerates and drill samples, suggest flowing water, whereas the minerals in the younger soil are consistent with limited interaction with water.

September 23: Broxton Bird, IUPUI. Title: New perspectives of Holocene tropical hydroclimates from high-resolution lake sediment archives.

Abstract: Monsoons are a central component of the global climate system that provide more than half of the world’s population with fresh water. Despite this, surprisingly little is known about the mean state of these systems and their variability at decadal timescales during the Holocene. Lakes and their sediments are well suited for investigating monsoonal variability because they archive a diverse range of environmental information at high temporal resolutions and are distributed globally. Through measurements of the physical and geochemical properties of lake sediments, it is possible to reconstruct the long-term behavior of critical monsoon processes at local and synoptic scales. In this talk, I will present results from a lake-sediment-based paleoclimate investigation from tropical South America that shed new light on the South American summer monsoon (SASM) mean state and how it varied during periods of rapid Holocene climate change.

September 30: Michael Hamburger and Gary Pavlis, IU Geophysics. Title: What’s a Nice Earthquake Like You Doing in a Place Like This? Understanding Earthquake Generation in North America’s Cratonic Interior.

October 7: Alan Jay Kaufman, University of Maryland Title: A Shorter Fuse for the Cambrian Explosion?

Abstract: Well-preserved strata of the Khorbusuonka Group in the Olenek Uplift, arctic Siberia provide important sedimentologic, chemostratigraphic, and radiometric constraints on the demise of the Earth’s earliest metazoans and the subsequent Cambrian Explosion. Ediacara fossils in bituminous limestone of the Khatyspyt Formation occur as three dimensional casts and as carbonaceous compressions, whereas the earliest small shelly fossils of Cambrian aspect (Anabarites trisulcatus Zone) are preserved in dolomite of the overlying Turkut Formation. The upper reaches of Turkut Formation are variably truncated and overlain by the Kessyusa Group, a new stratigraphic subdivision including widespread diamictite in the Tas-Yurakh Formation, which is interbedded with tuff breccia dated at ca. 543 Ma, as well as mixed siliciclastic and carbonate of the Syhargalakh and Mattia formations. Small shelly fossils in the lower reaches of the Mattia Formation include elements of the Purella antiqua Zone, which is overlain with fossils of the basal Tommotian Nochoriocyathus sunnaginicus Zone only a few meters higher. High resolution sampling and carbon isotope analysis of Mattia Formation carbonates define a positive excursion up to +5‰ associated with 87Sr/86Sr compositions as low as 0.70818. A white clay layer collected from near the top of the Mattia Formation interpreted as a volcanic ash yielded abundant euhedral zircons, which were measured by both LA-ICP-MS and TIMS techniques. U-Pb dates determined by both methods suggest an age around 529-530 Ma for the sample. These results suggests that the base of the Tommotian Stage of the Cambrian Period is some 4-5 million years younger than previously estimated. Furthermore, the new age constraint coupled with biostratigraphic and isotopic data from the same succession indicate that the fuse for the Cambrian Explosion may have been several million years shorter, perhaps lasting only 10 million years after a potential glacial episode near the Ediacaran-Cambrian boundary.

October 14: Rudy Raff, Distinguished Professor and James H. Rudy Professor of Biology. Title: To fossilize or to destroy? That is the question. Microbial ecology in soft tissue taphonomy.

Abstract: The fossil Ediacarian animal embryos embryos from Dushantuo have always seemed an enigma to me. We work with marine embryos, and so I was intrigued by a question asked by a paleontology colleague in Britain. Did I think embryos could be fossilized? I thought it unlikely because killed embryos self destruct within hours of death, but promised to take a look. That innocent pledge has led us to see what biological processes might contribute to something nearly as delicate as a soap bubble becoming an organic object that ultimately could be mineralized. The answer is that it can, but there are a lot of non-intuitive things going on. I’ll talk about how we are exploring this question, and the surprising results that we found about how bacteria can preserve the structure of soft tissue.

October 21: Alyssa Shiel, University of Illinois Urbana–Champaign. Title: Non–traditional stable isotopes for tracing metals in the environment.

October 27-30: No Colloquium, GSA week

November 4: James Conder, Southern Illinois University Title: What we know about the Wabash Valley Seismic Zone and what we would like to know.

November 11: Eva Enkelmann, Department of Geology, University of Cincinnati Title: Tectonics and Surface Process Interaction at the Yakutat Plate Corner, SE Alaska

Abstract: The Yakutat – North American collision zone in southeast Alaska is one of the most active tectonic regions on Earth and formed the highest coastal mountain range–the St. Elias Mountains. Large ice fields and glaciers cover more then 50% of this regions surface and shape the landscape by actively eroding material that is transported into the Gulf of Alaska. The St. Elias Range is an excellent natural laboratory to study interaction between surface and tectonic processes and has attracted many scientists that generated a large dataset of geophysical and geological observations. Various geo- and thermochronometric ages derived from bedrock and detrital material have been produced over the past 15 years, revealing the complex pattern of differential rock exhumation across the orogen. The rock exhumation correlates with structures as well as with climatic patterns, but the syntaxial region of the St. Elias Mountains, where the Yakutat plate corner is colliding and strike-slip motion transients into convergence, stands out as it reveals the most rapid and deep exhumation then elsewhere in the region.

November 18: Nick Wigginton, Associate Editor, Science magazine. Title: Scientific Publishing from the Inside–Out.

Abstract: The expectations for researchers as authors of peer-reviewed manuscripts have never been higher. Emerging issues related to scientific publishing (e.g., data sharing, new publication/review models, measuring impact, open access) contribute to the ongoing rapid evolution of scientific publishing. Although publishing continues to be the primary means of scholarly communication, many of these issues are rarely addressed in the classroom or lab. Dr. Wigginton will discuss various aspects of scientific publishing – including the importance of peer review and planning for publication – from the perspective of an Associate Editor at Science, where he is responsible for handling manuscripts in the broad areas of Earth and environmental science.

November 25: No colloquium, Thanksgiving Break

December 2: Sergio Fagherazzi, Boston University. Title: Nonlinear dynamics and alternative stable states in shallow bays.

Abstract: The dynamics of shallow-water coastal environments are controlled by external drivers-sea level rise, storms, and sediment and nutrient supplies-and by internal feedbacks. Interactions of biotic processes (vegetation growth, trophic dynamics) and abiotic drivers can lead to nonlinear responses to changing conditions and to the emergence of thresholds, hysteresis, and alternative stable states. Here I am presenting a conceptual framework for studying interactions between the dynamics of marshes and habitats in shallow coastal bays with unconsolidated sediments (seagrass, oyster reefs). Two stable states are present in intertidal areas, with salt marshes lying above mean sea level and tidal flats below mean sea level. State transitions are driven by sediment availability, sea level rise, the relative strength of wind waves with respect to tidal currents, and the biotic feedback of vegetation on sediment stabilization and accretion. State-change dynamics in one system may propagate to adjacent systems, and this coupling may influence the landscape-scale response to environmental change. Forecasting the resilience of coastal ecosystems and the landscape-scale response to environmental change in the next century requires an understanding of nonlinear dynamics, including the possibility of multiple stable states, the coupled evolution of adjacent systems, and potential early warning signs of thresholds of change.

December 9-13: No colloquium, AGU week

December 16: No colloquium, final exam week