Spring 2006 Colloquia

Wednesday, January 18 Dr. Kitty Milliken, University of Texas AAPG Distinguished Lecturer. Title: Linked Mechanical and Chemical Processes in the Diagenesis of Sandstones

imageCathodoluminescence imaging has served to reveal previously unrecognized linkages between brittle processes and cementation in a wide variety of diagenetic settings. Because nucleation of quartz cement is highly localized on pre-existing quartz substrates, fracture processes enhance the potential for quartz cement emplacement by creating favorable surfaces. This phenomenon is observed in the context of burial compaction, in deformation bands, in quartz-rich fault gouges, and in tectonically-produced transgranular fractures. In each case the amount of quartz cementation is greater than the amount that would occur in the absence of fracturing. In turn, the quartz cementation imparts changes in the mechanical properties of sandstones. The conceptual framework that emerges from these observations is one in which mechanical and chemical properties of sandstones evolve in concert. Reservoir quality assessment in rocks that have experienced a protracted history of diagenesis requires approaches that explicitly acknowledge the genetic links between chemical and mechanical processes.

Monday, January 23Dr. Jay LaVerne, University of Notre Dame. Title: Radiation Chemistry Studies with Heavy Ions

Energy deposition by the passage ionizing radiation in matter can lead to significant chemical change. The effects of radiation are important in many applications involving health, industry, and the environment. An overview of radiation chemistry will be given and will include a thorough description of the radiolysis of liquid water. Radiation chemical processes are often strongly dependent on the type of radiation. For example, product yields in gamma radiolysis can be very different from that observed with alpha particle radiolysis. The physical and chemical basis for the variation in radiolytic processes with particle type will be explained. Radiolytic processes occurring at interfaces will be discussed.

Tuesday, January 24 - 5:00 p.m. Glenn Black Lab Auditorium. Dr. Thomas Foster, Northern Kentucky University. Title: Ecological and Social Adaptation of the Creek Indians: Global Implications from Local Research

The Talk will be a synthesis of Dr. Foster's research program, which is interdisciplinary, holistic, and problem oriented. It is focused toward understanding how humans adapt to changing social and ecological environments and is applicable worldwide. I use archaeological, ethnohistoric, and ecological data with GIS in order to understand how Indians of the southeastern United States adapted to changing environments. Dr. Foster will discuss how he uses archaeology, historic witness tree data, and palynology research to quantify the anthropogenic effects of the Historic Period (1715-1836) Creek Indians on their forests. This research, which has been applied to modern environmental management, is beginning to correlate human effects on the distribution of trees such as hickory, pine, and early succession species with specific economic activities of the Indians. Dr. Foster's models of their horticultural economies indicate that the Southeastern Indians used risk management to deal with economic and environmental variability and have implications for the development of complex societies in the Southeast. In collaboration with the descendant tribes, Dr. Foster is currently directing archaeological fieldwork that is contributing to our understanding of how the Creek Indians adapted to the colonial frontier, their environment, and to each other. This research on the cultural heritage of the Historic Period Creek Indians shows that they adapted at varying rates and in varying degrees.

Tuseday, January 31 - 12:15 p.m. @ Patton Room S201. Dr. Robert C. Burruss, U.S. Geological Survey, Energy Resources Program. Title: CO2 sequestration

Monday, February 13Dr. Brian Currie, Miami University of Ohio. Title: Eocene-Miocene paleoaltimetry of the Tibetan Plateau

The stable-isotopic composition of lacustrine and pedogenic carbonates from the Hoh Xil, Lunpola, and Oiyug basins of Tibet allow model estimates of the paleoaltimetry of the Tibetan Plateau for the Eocene-Miocene. Lacustrine carbonates from the Middle Eocene Fenghuoshan Group of the Hoh Xil basin in northern Tibet have δ18O values ranging from –11.7‰ to –10.26‰ (PDB). Model results using these values indicate the hypsometric mean elevation of the drainage basins feeding Hoh Xil lakes ≤ 2 km. In the Lunpola basin of central Tibet, Eocene-Oligocene Niubao Fm. lacustrine limestones and marls have δ18O values of –2.9‰ to –13.8‰ (PDB), while pedogenic carbonates from the same unit have average δ18O compositions of –17.1‰ ±1.7‰ (PDB). Model results using these compositions yield predicted paleoelevations for the basin of 4.0-4.6 km. The oxygen isotopic composition of lacustrine marls and micritic limestones from the Miocene Dingqing Formation from the Lunpola basin range from –0.4‰ to –14.6‰ (PDB). Model results using these compositions yield predicted Miocene paleoelevations of ˜4.2 km. Pedogenic carbonates from the Rigonla Formation in the Oiyug Basin of southern Tibet have δ18O values -20.2‰ which indicates surface elevations ˜5.3 km prior to 15 Ma.

Collectively, these results indicate that the southern and central Tibetan plateau achieved elevations similar to those that presently exist by ≥15 Ma, and for the Lunpola region of central Tibet at > 34 Ma. To date, the data from the Fenghuoshan Group are the only indications of relatively lower elevations (≤ 2 km) for any part of the present-day Tibetan Plateau since the Middle Eocene and suggests that the northern boundary of the plateau during the Eocene was situated between the Lunpola and Hoh Xil basins. This suggests that uplift of the Tibetan plateau has progressed northward through time and that the northern part of the plateau has experienced uplift in excess of 2.7 km since ˜36 Ma. Exactly when uplift of the northern plateau occurred, however, has yet to be resolved.

Friday, February 17 - 12:00 noon in the Patton Room S201. Dr. John Swenson, University of Minnesota Duluth Title: Clinoform Dynamics and Shoreline Response to Eustasy: Relative Importance of Fluvial Input and Basin Energetics

Monday, February 20 Dr. Don Siegel, Syracuse University Title: Deflating the Soufflé: The Coupling of Carbon Geochemistry and Hydrogeology of the World’s Large Peatlands

imageBog peat is an elastic porous medium, capable of expanding and contracting as a function of degree of saturation and changes in pore water chemistry. I report the discovery that the transient production of over pressured gaseous methane in the middle of humified bog peat (Glacial Lake Agassiz Peatlands, MN) reverses natural hydraulic gradients and causes peat to expand and contract as a function of gas production and barometric pressure differences. This expansion increases the land surface elevation up to 20 cm. After the peat expands, methane episodically degasses to the atmosphere, exceeding the annual average chamber fluxes measured by >10 times.

After degassing, the landscape "deflates" until the peat re-saturates with water and re-expands to pre-event hydraulic conditions. Watertable mounds under the bogs recharge modern labile carbon down to the deep zones for methanogenesis, while the saturation of the deeper peat layers is maintained by regional groundwater discharge from mineral soils below. The hydrobiogeochemistry of peatlands is far more dynamic than previously thought, and closely tied to climate change.

Tuesday, February 21 - 12:00 noon in the Patton Room S201 Dr. Don Siegel, Syracuse University Title: Hydrogeologists in the Court Room: Ethics versus Sciences

Monday, February 27 Dr. Walter Mooney, U.S. Geological Survey, Earthquake Hazards Program. Tudor lecture Title: The Great Sumatra-Andaman Islands Earthquake and Tsunami: Observations and Regional Preparations for Future Tsunamis

imageThe December, 2004, Sumatra-Andaman Islands earthquake and tsunami caused an estimated 280,000 deaths in the Indian Ocean region. This enormous (M = 9.2) earthquake was recorded by modern field instrumentation and has led to profound insights into the origin of great earthquakes and the tsunamis they generate. This talk will summarize the scientific state-of-the-art regarding this devastating earthquake, and will discuss plans to avoid such disasters in the future.

Monday, March 6 Dr. Huifang Xu, University of Wisconsin-Madison

Monday, March 20 Dr. Peter Eng, University of Chicago, GeoSoilEnviroCARS

Monday, March 27 Dr. Gabriel Filipelli, Indiana University-Purdue University at Indianapolis. Title: A cure for global warming? A critical look at iron fertilization’s role in climate change using Ocean Drilling Program cores

"Give me a tanker of iron, and I'll give you an Ice Age." This quote by Dr. John Martin referred to the fact that the equatorial oceans and the Southern Ocean (surrounding Antarctica) harbored more plant life during Ice Ages, a result of enhanced delivery of dust providing the iron necessary for plant growth, which in turn extracted carbon dioxide from the atmosphere and caused global cooling (The "Iron Hypothesis"). Faced with a new era of human-produced global warming, a number of eco-engineering programs are underway to enhance this "natural" process by artificial fertilization. To examine how "natural" this process was in the past, Filippelli has utilized the record of iron and biological productivity stored in deep sea cores recovered from the Southern Ocean, including during a stint as a Shipboard Scientist on ODP Leg 177. Results indicate that the "natural" source of iron to the Southern Ocean was from below via upwelled water and not from seeding of the surface by dust, and the stability and bioavailability of this natural upwelled source may not be matched by eco-engineering solutions.

Monday, April 3 Dr. Jennifer McIntosh, Johns Hopkins University. Title: Hydrogeochemical controls on microbial gas generation in Upper Devonian fractured black shales: Illinois, Michigan, and Appalachian basins

Relatively recent microbial activity has generated economic deposits of methane within fractured Upper Devonian black shales along the shallow margins of the Illinois, Michigan, and Appalachian basins. Meteoric waters recharged regional Silurian-Devonian aquifer systems along the basin margins, during Pleistocene glaciation, and migrated vertically into the overlying organic-rich shales, significantly diluting basinal fluid salinities and creating an environment conducive to microbial methanogenesis. Results from integrative studies of shale formation waters, gas, crushed core analyses, microbial populations, and hydrologic modeling will be presented.

Antrim and New Albany shale formation waters, in the Michigan and Illinois basins, respectively, have positive δ13C values for CO2(g) and dissolved inorganic carbon (DIC, >+20 ‰), and high DIC concentrations (10-70 meq/kg), indicative of methanogenesis. The covariance of δD values for CH4 and H2O indicate methane was generated by CO2 reduction in-situ with dilute fluids and adsorbed onto the organic matrix. Carbon isotope values of CH4 range between suggested fields for microbial versus thermogenic gas, and in some cases are more positive than basin-centered thermogenic gas plays. Carbon isotope values of ethane and propane increase with decreasing concentration due to microbial oxidation of these thermogenic gas components. Selective enrichment cultures and DNA studies of Antrim Shale fluids show methanogens and acetogens associated with this unique gas resource.

Monday, April 17 Dr. Lucy Flesch, Purdue University Title: Constraining the extent of crust—mantle coupling in central Asia using GPS, geologic, and shear wave splitting data

We have obtained constraints on mechanical crust—mantle coupling for Tibet and Yunnan/Indo China, by comparing the observed surface deformation field inferred from GPS and Quaternary fault slip rate data, with the mantle deformation field inferred from several SKS shear wave splitting data sets. We first determined whether the anisotropy is dominantly asthenospheric or lithospheric by testing simple models of both types against the observed values of the fast polarization direction, /, which is assumed to be parallel to the horizontal projection of the direction of maximum shear. For asthenospheric flow, we solved for a best-fitting uniform sub-asthenospheric velocity model for Eurasia. The fit, however, was not satisfactory (RMS misfit D/ =208). Solving for separate uniform flow fields in each region improves the fit (D/ =158 for Tibet, D/ =118 for Yunnan), although the resulting flow fields are inconsistent with several geophysical and geological constraints and thus considered unlikely. We then considered lithospheric models. For Tibet, vertically coherent deformation (i.e., maximum shear direction from surface deformation is parallel to /) yields an improved match (D/ =118) for left-lateral shear. Both the goodness of fit and the dominance of left-lateral surface faulting in Tibet, argue for a lithospheric source of anisotropy. The misfit for Yunnan is large for either right- (D/ =538) or left-lateral (D/ =498) shear, which argues for complete crust—mantle decoupling in Yunnan. We show that the fast polarization directions throughout both the Tibet and Yunnan region can be fit by a single lithospheric dynamic model in which there is strong coupling between crust and mantle beneath Tibet, but a complete decoupling between crust and mantle beneath Yunnan crust. This dynamic model predicts left-lateral maximum shear directions within the mantle that align with fast polarization directions in both regions (D/ =98). These maximum shear directions within the mantle align with the left-lateral maximum shear directions in the crustal deformation field in Tibet, but are not in Yunnan. Our results have the following implications. First, the coherence between crust and mantle deformation in Tibet implies strong crust—mantle mechanical coupling, since this is the only way that crustal buoyancy forces, required to account for the surface deformation field, can be transmitted into the mantle. This behavior is consistent with a uniform-strength lithosphere or strong crust, but not with a substantially weaker crust. For example, it is inconsistent with the popular bjelly-sandwichQ rheology, and thus precludes behavior such as large-scale lower crustal flow in Tibet. The crust—mantle coherence is also incompatible with mantle delamination. Second, crust—mantle decoupling within the Yunnan lithosphere argues that mantle deformation there is controlled only by boundary conditions; crustal buoyancy forces are not transmitted into the mantle beneath Yunnan. Moreover, the dynamic model for the mantle shows that the Yunnan crust is moving south with respect to the mantle at rates as high as ˜30 mm/yr. Third, there is a fundamental rheological lithospheric transition between Tibet and Yunnan that may provide a key to understanding this significant orogen.

Monday, April 24 Dr. Lindsay Schoenbohm, Ohio State University. Title: The Growth and Death of Plateaus: Examples from the Andes and Tibet

Continental plateaus, such as the Tibetan Plateau and the Altiplano-Puna plateau in the central Andes, are the result of exceptional tectonic and climatic conditions. A number of different mechanisms have been proposed for their formation, development and eventual demise, including: underthrusting, distributed shortening, magmatic addition, lithospheric thinning, extensional collapse, lower crustal flow, and development of internal drainage. I will argue in this presentation that in fact all of these mechanisms appear to be operating in both of the major examples of plateaus, in Tibet and the Andes.

In the Andes, there is an active magmatic arc, the Brazilian craton may be underthrusting the eastern Andean ranges, and both thin- and thick-skinned deformation is found throughout the plateau. Climatic factors affect the growth of the southern plateau, where defeat of drainages and formation of internally-drained basins appears to be important. I will present new mapping along the southern margin of the plateau which suggests a profound shift in the Quaternary from regional shortening to extension within the plateau. This could be the result of lithospheric delamination or extensional collapse, but certainly reflects a new phase in the growth of the Andean Plateau. In Tibet, most of these same modes of growth and development of the plateau can be identified. Additionally, there is compelling evidence for the flow of weak middle to lower crust from beneath the Tibetan Plateau into the surrounding regions. I will present evidence for the propagation of this material into the southeast margin of the Plateau. In sum, plateaus result from a combination of different, interacting mechanisms. Initial crustal thickening, regardless of the form which it takes, results in weak, gravitationally unstable crust, which leads to lithospheric delamination, lower crustal flow and extensional collapse. Plateaus also create their own arid climate, leading to internal drainage, which may help sustain plateau morphology.