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Spring 2015 Colloquia

Thursday, January 29, 2015

Dr. Roberto Iannuzzi, Departamento de Paleontologia e Estratigrafia
Title: The Glossopteris Floras: synthesis, problems and perspectives. Description/
Host: John Isbell

Abstract:
The presentation offers a historical overview of the concept of Gondwana and the Glossopteris Flora in terms of the floras origin, rise and disappearance. The talk will also address the phytogeographical significance of the flora and its importance to paleoclimatic studies and the possible contribution of the floral elements to the evolution of land plants. The talk will conclude by addressing the problems and challenges faced in advancing our knowledge of this flora.

Thursday, February 5, 2015

Dr. Greg Wiles, Professor at Wooster College
Title:North Pacific Climate Variability as Recorded in Tree Rings at Coastal Sites from Alaska and the Russian Fareast
Host: Erik Gulbranson

Abstract:
We have developed a network of living tree-ring chronologies from coastal forests along the North Pacific Rim that are sensitive to North Pacific air-sea interactions. Long records are being developed using dendrochronology on wood collected in the wake of retreating glaciers in the region. These records record annual to millennial-scale climate variability and have the potential to extend the observational record of temperature and derived climate indices back through much of the Holocene.

Thursday, February 12, 2015

Dr. Shaun Marcott, UW-Madison
Title: Atmospheric Carbon Dioxide Changes Over the Last 70,000 years
Host: Julie Bowles

Abstract:
Two long-standing questions in carbon cycle dynamics are what caused the glacial-to-interglacial rise in atmospheric carbon dioxide (CO2) during the last glacial termination and what factors contributed to the millennial scale variations during Marine Isotope Stage 3 (MIS 3) from approximately 70,000 to 25,000 years before present. The enduring paradigm is that the underlying processes are related to the Southern Ocean, and operate at millennial (or longer) time scales, which is largely based on the strong covariance of CO2 with Antarctic temperature. In this talk I will present a CO2 record spanning the last glacial and deglacial periods from the West Antarctic Ice Sheet Divide ice core (WDC), which has a sampling resolution of 25-150 yr. This work provides new evidence that a centennial scale component of atmospheric CO2 variability exists during both the CO2 rise of the last termination, and the more rapid oscillations of MIS 3.ne.

Thursday, February 19, 2015

Dr. Kathleen Ritterbush, University of Chicago
Title: Paleoecological consequences of the Triassic/Jurassic mass extinction and the significance of biosiliceous “glass ramps”
Host: Margaret Fraiser

Abstract:
Marine carbonate habitats destabilized during the Triassic/Jurassic mass extinction 200 Myr ago. New field work from North and South America shows early Jurassic shallow ramps dominated by sliceous sponges. The ecological and geochemical conditions that allowed the sponges to flourish, both after the extinction and at other times in Earth history, are explored. Ultimately, the ecological changes both during the extinction crisis and the following 2-4 million years of recovery are heavily influenced by large-scale tectonics, volcanism, climate and geochemical cycling.

Thursday, February 26, 2015

Dr. Sally Potter-McIntyre, Southern Illinois University Carbondale
Title: Jurassic Fluvio-lacustrine Formations on the Colorado Plateau: Informing Astrobiological and Sedimentological Research at Gale, Crater, Mars
Host: Weon Shik Han

Abstract:
In August, 2012, the Mars Science Laboratory (MSL) rover, Curiosity, landed in Gale Crater to investigate clay-rich sedimentary rocks, possibly of a lacustrine origin and recently much research is being published with exciting results – even claiming the first habitable environment documented outside of Earth. The Jurassic Wanakah Formation, and the Tidwell and Brushy Basin Members of the Morrison Formation are proposed as terrestrial analogs to the Yellowknife Bay formation in Gale Crater. All three of these units have similarities in depositional environments and lithologies. The Wanakah Formation and the Tidwell Member were deposited in hypersaline lake environments and the upper part of the Brushy Basin Member represents a fluvio-lacustrine lake that was at times circumnuetral and at times an alkaline saline lake environment. During the middle to late Jurassic, a back arc basin to the west input abundant volcanic ash into the cratonic basin in what is now the Colorado Plateau region of the USA. Biodiversity (recorded in trace fossil and microbial fossil assemblages) is correlated to fluid chemistry (influenced by episodic volcanic ash input to the lake system) and different diagenetic facies show associated and distinct biotic signatures, i.e., reduced sediments show restricted biodiversity limited to algal mat trace fossils (vugs) and oxidized sediments host more diverse trace and microbial fossil assemblages. Additionally, microbes are producing identifiable mineralogical, textural and chemical biosignatures that are preserved throughout geologic time.

Thursday, March 6, 2015

Mike DdeVasto, GZA Environmental
Title: Structural controls and implications for an ore-shoot in the Raven deposit, Kensington Gold Mine, Alaska, Juneau.
Host: Dyanna Czeck

Abstract:
A structural analysis was conducted on a narrow vein deposit at the Kensington gold mine. Unlike the greater Kensington deposit that is defined by high density extension vein arrays, the Raven vein is a massive auriferous vein hosted within a third order fault-shear zone. This study focuses on a qualitative description and a kinematic analysis of the vein sets, where a basic field approach using fundamental skills can create a significant impact on grade control, drilling programs, and resource estimation. A set of veins occur within the third order fault-shear zone; a NW-SE striking quartz+calcite+/-sulfide vein sub parallel to the shear zone foliation with galena lamina, stylolites, and relatively lower grade. In contrast, a large quartz+calcite+sulfide rich vein strikes N-S within the fault-shear zone with well-formed textures and significant alteration halo. Structurally these veins are disparate; the NW striking vein lies within the theoretical zone of shortening and the N-S striking vein is on the cusp of the shortening-extension field. Recognition of a C’ fabric in the fault-shear zone through underground mapping yields a plausible mechanism for decoupling of the crust during progressive strike-slip deformation – creating an ideal site for hydrothermal deposition. I believe the formation of this fabric induced a small-scale extensional regime within the shear zone, allotting for hydrothermal fluid to deposit. Furthermore, analysis of the 3-D distribution of high grade ore within the main vein of the Raven matches well with measured and theoretical ore-shoot directions, implying potential for ore-shoot analysis in similar gold deposits.

Thursday, April 2, 2015

Dr. Gary Acton, Sam Houston State University
Title: A Dynamic Geomagnetic Field Revealed From Coring a Constellation of Paleomagnetic Stations in the Ocean Basins
Host: Julie Bowles

Abstract:
Scientific ocean drilling provides a unique means for accessing a part of the geologic history of Earth locked beneath the oceans. Over the past 56 years, hundreds of kilometers of drill core and many millions of measurements of physical, chemical, and magnetic properties along these cores have been collected and studied in great detail, yielding a much greater understanding of how Earth works. In my talk, I will provide a tour of several ocean drilling expeditions on which I have participated that span the oceans from Antarctica to the Arctic and that investigate topics from climate change to large geomagnetic field fluctuations. This tour will illustrate the “life” of a core, from the methods used to collect, process, and measure cores to the results that reveal abrupt climate change events that have occurred over Earth’s recent geologic history.

Thursday, April 9, 2015

Dr. Bill Hammer, Augustana College
Title: New Sauropodomorph Dinosaurs from the Jurassic of Antarctica
Host: Katie Pauls and John Isbell

Abstract:
Two new genera and species of sauropodomorph dinosaurs were discovered during the 2010-11 field season in Jurassic deposits on Mt. Kirkpatrick in the Southern Transantarctic Mountains. One of the specimens is a nearly complete skeleton of a juvenile while the second taxon is represented only by parts of the pelvis, leg and vertebral column. Along with the previously described Glacialisaurus there are now three sauropodomorphs from the Jurassic of Antarctica. While the three Antarctic sauropodomorphs represent taxa that are not found in other parts of Gondwana they are not closely related to one another and hence do not belong to the same clade. Glacialisaurus belongs to a clade that includes Lufengosaurus from China, the new juvenile belongs to a clade that includes Leonearas Ignavusaurus from South Africa and the third sauropodomorph belongs to a clade that includes Leonearasaurus from Brazil.

Thursday, April 16, 2015

Art Kasson, Product Manager, IRMS, elementar Americas Inc.
Title: Introducing the VisION Isotope Ratio Mass Spectrometer, the future of IRMS from elementar.
Host: Linsday McHenry

Abstract:
We present the very latest in Isotope Ratio Mass Spectrometer (IRMS) technology from elementar – the VisION.

From our position as a dedicated and leading global supplier of IRMS instrumentation, we have carefully evaluated how today’s scientists use IRMS in the modern laboratory to generate high quality isotope data, ultimately informing and developing their respective scientific community’s understanding of stable isotope systems. Using this insight we believe that IRMS needs to be more accessible, more efficient and more powerful than ever before leading to the creation of a completely new IRMS experience. In particular, we find a growing interest in the power of IRMS from a wide variety of scientists who would otherwise believe IRMS instrumentation to be inaccessible, whether due to perceived complexity of the required instrumentation, or simply believing that IRMS is too demanding in terms of investment for their laboratory. We aim to deliver the powerful tool of stable isotope analysis to these new users with a new IRMS experience while continuing to bring tangible benefits to those experienced laboratories who require high powered yet fully automated IRMS for turnkey analysis; this is our prediction for the future of IRMS, the VisION.

We will demonstrate how the powerful new features of VisION such as IonOS software and CentrION Monitoring Gas System will lead to a new way of working with IRMS, allowing new and experienced users alike to benefit from time and effort-saving automation features. We will also demonstrate how the VisION is uniquely focused upon specific application solutions which will enable modern IRMS researchers to generate accurate and precise results quickly with the highest confidence across multiple fields of study.

Thursday, April 23, 2015

Dr. Emily Finzel, Earth & Environmental Sciences, University of Iowa
Title: Provenance signature of changing plate boundary conditions along a convergent margin: detrital record of spreading-ridge and flat-slab subduction processes Cenozoic forearc basins, Alaska
Host: John Isbell

Abstract:
Cenozoic strata from forearc basins in southern Alaska record deposition related to two different types of shallow subduction: Paleocene-Eocene spreading-ridge subduction and Oligocene-Recent oceanic plateau subduction. We use detrital zircon geochronology (n = 1368) and clast composition of conglomerate (n = 1068) to reconstruct the upper plate response to these two subduction events as recorded in forearc basin strata and modern river sediment. Upper plate processes associated with subduction of a spreading ridge resulted in an abrupt increase in the diversity of detrital zircon ages that reflect new sediment sources from far inboard regions. The detrital zircon signatures from strata deposited during oceanic plateau subduction record exhumation of the region above the flat slab, with the youngest detrital zircon population reflecting the last period of major arc activity prior to insertion of the flat slab. This study provides a foundation for new tectonic and provenance models of forearc basins that have been modified by shallow subduction processes, and may help to facilitate the use of U-Pb dating of detrital zircons to better understand basins that formed under changing geodynamic plate boundary conditions.

Friday, April 24, 2015

Dr. Esther Stewart, Precambrian Geologist at Wisconsin Geological and Natural History Survey
Title: Microbially Induced Sedimentary Structures and Large Sand Stromatolites in the Terrestrial and Marine/lacustrine-transitional Bayfield Group (Proterozoic), Wisconsin
Host: John Isbell

Abstract:
The Proterozoic Bayfield Group is the youngest of the post-rift sediments that infilled the ~1Ga Midcontinent Rift in northern Wisconsin. It is generally accepted that these rocks were deposited by rivers and lakes after rifting of the Midcontinent Rift subsided, a little after 1 billion years ago. However, recent observations suggest the Bayfield Group rocks may be significantly younger and were deposited in environments that varied from river, to desert, to lake or even marine. In this presentation I will discuss microbially induced sedimentary structures (MISS) in the eolian Devils Island Sandstone and 0.5 to >1 meter-scale sand stromatolites within a lacustrine or marine unit at the base of the Chequamegon Sandstone. Documentation of MISS in eolian facies adds to increasing evidence for significant microbial modification of Precambrian terrestrial settings. Meter-scale sand stromatolites are among the largest documented, likely significant for understanding Bayfield Group paleoenvironment.