September 27, 2005
Mid-Tertiary transition from plate-like to continuous deformation in NE Tibet
BRAD RITTS
INDIANA UNIVERSITY Whether Cenozoic India-Eurasia convergence has been accommodated by plate-like extrusion or distributed shortening within the Tibet Plateau has been a long-standing debate. Geodetic studies by numerous groups suggest that shortening is accommodated continuously across Tibet and that slip rates on major strike-slip faults are slow, consistent with predictions of distributed shortening models. However, longer-term geologic records of translation on the Altyn Tagh fault (ATF) as well as shortening and uplift on the NE margin of the Tibet Plateau, suggest that rates and styles of deformation changed in the mid-Miocene. Tertiary basins on the ATF are offset from their sources in the Qilian Shan by slip on the ATF. These sediment-source matches provide Oligocene, Early Miocene, mid-Miocene and Pliocene piecing points that demonstrate that most of the 375±25 km of total displacement on the ATF accumulated in the Oligocene and earliest Miocene, and that relatively small amounts of offset have occurred since the Early Miocene. These offsets, suggest a Late Oligocene-Early Miocene slip rate for the ATF in excess of 17 mm/year and post-Early Miocene slip rates of <10 mm/year. Thermochronologic and stratigraphic evidence also support mid-Tertiary shortening and uplift of the Kunlun and Qilian thrust belts, with rapid exhumation and propagation of thrust belts occurring in the Miocene and younger. Finally, we have identified strike-slip faults that extend northeast of the Tibet Plateau that potentially have slip histories that are very similar to the ATF. These faults, with large pre-Miocene offsets, and little post-Miocene activity, may extend to the Pacific margin. We interpret these changes in rates and styles of deformation as a reorganization of intraplate tectonic style in the Miocene, from plate-like to distributed accommodation of India-Eurasia convergence. Evidence for rapid strike-slip on the ATF before the mid-Miocene, and mapping of pre-Miocene structures that extend beyond the plateau and could have accommodated extrusion of Tibet are consistent with an early phase of plate-like extrusion. Initiation of rapid shortening and propagation of thrust belts in the Miocene of the Qilian Shan, Altun Shan, and Kunlun Shan suggest that deformation was more widely distributed in the later Tertiary and that deformation had become more continuous across the region. The change in tectonic style may have been related to changes in India-Eurasia convergence, mechanics of Tibet lithosphere, or confinement along the free-face at the Pacific margin. Submitted to: 2005 AGU Fall Meeting
October 4, 2005
Ground Water Model Predictions To Guide Field Data Collection
CLAIRE TIEDEMAN
USGS
This talk will present (1) methods for using a calibrated model of any natural system to guide collection of field data that are important to the model predictions, and (2) an application of the methods to a regional ground-water model. Data are considered important if they would help reduce model prediction uncertainty. The methods address two different types of data. First, the parameter-prediction (ppr) statistic identifies model parameters that are most important to the predictions. This statistic helps guide collection of field data that are related to model parameters, such as hydrogeologic unit characteristics, hydraulic conductivities, and recharge values in ground-water models. Second, the observation-prediction (opr) statistic identifies the importance of existing and potential system-state observations to the predictions. This statistic helps guide collection of new observation data, such as hydraulic heads, flows, and concentrations in ground-water models. The ppr and opr statistics are applied to a model of the Death Valley regional ground-water flow system, to help guide collection of field data that would reduce the uncertainty of predicted ground-water transport paths from beneath Yucca Mountain and the Nevada Test Site.
October 11, 2005
Plate Tectonics and Ice Ages; Animating the Earth!
TANYA ATWATER
UCSB
Dr. Atwater is a renowned scientist, a deeply committed and creative teacher and a very lively speaker! She was educated at M.I.T., U.C.Berkeley, and Scripps Institute of Oceanography, then joined the U.C.S.B. faculty in 1980. Her research concerns many aspects of plate tectonics, with special attention to the evolution of western North America and the San Andreas fault system. She teaches at all levels, including many public education projects. Her honors include an N.S.F. Directors Award for Distinguished Teaching Scholars, the G.S.A. Structure and Tectonics Best Paper Award, and election to the National Academy of Sciences in 1997. Dr. Atwater runs the UCSB Educational Multimedia Visualization Center which produces educational geo-animations and visualization tools. To download animations, visit http://emvc.geol.ucsb.edu/.
October 26, 2005
Rumblings From The Deep: Deciphering The Birth And Death Of Earth's Surface
Wednesday at 12 Noon in Earth and Marine Sciences Bldg Room A340**
EDWARD GARNERO
ARIZONA STATE UNIVERSITY
While the most fundamental feature of interiors of large planetary bodies is layering/stratification, the creation and destruction of Earth's outermost rigid shell at mid-ocean ridges and subduction zones, respectively, mountain building, earthquakes, and volcanic activity (for example), all point to dynamical processes within the interior that must certainly go far beyond simple internal layering. However, Earth's deep interior is predominantly inaccessible, since one can only drill several miles deep, and volcanic activity only very rarely involves material thought to originate from below a couple hundred miles or so. We are thus left with the question: how can the rest of the interior, nearly 4000 miles of material down to the center, be confidently interrogated? And furthermore, can we characterize deep structure and processes at a level that reveals the connection between the making of Earth's surface and its interior? Using seismic imaging techniques, we are now getting glimpses of exotic internal structures at a variety of spatial scale lengths: from several kilometers to 1000's of km. While there is certainly so much that lies before us awaiting discovery, we are now seeing connections between hot spot volcanoes and partially molten material half way to Earth's center at the base of the mantle. We are also detecting deep mantle seismic wave reflections (or echoes) off of former oceanic crust and lithospheric material, confirming the hypothesis that some tectonic plates submerge deep into the interior. In this presentation I will highlight several efforts aimed at deciphering Earth's enigmatic and unreachable interior, particularly those that have been conducted with, or have impact on disciplines beyond seismology, such as geodynamics, mineral physics, and geochemistry.
November 1, 2005
Rising mountain ranges: from earthquakes to geological deformation
JEAN-PHILIPPE AVOUAC
CALIF INSTITUTE OF TECHNOLOGY
November 8, 2005
Aerosol Indirect Effect: The elusive component of climate change
ATHANASIOS NENES
Georgia Institute of Technology
The effects of aerosols on clouds are recognized as one of the largest sources of uncertainty in assessments of anthropogenic climate change. This talk will address the importance of including explicit aerosol chemical composition information when studying aerosol-cloud interactions, and, recent advancements in developing general aerosol-cloud droplet modules for global climate models. In applying these general relationships, additional constraints on the activity and activation timescale of ambient CCN are required from in-situ observations; novel instrumentation and measurement techniques developed for fulfilling that requirement will be discussed.
November 15, 2005
Climate Effects on Regional Air Quality in California
MICHAEL KLEEMAN
U.C. DAVIS
November 22, 2005
Extremophiles, survivophiles, and the continuity of life on Earth
JONATHAN TRENT
NASA AMES Researach Center
I will describe "extremophiles" and "survivophiles" and consider their role in the continuity and perpetuity of life throughout Earth's turbulent history. The term "extremophiles" refers to organisms active in what are considered by human beings to be extreme physical or chemical environments. The term "survivophiles" collectively refers to organisms capable of assuming reversible inactive states (suspended or latent), which enable them to survive harsh conditions until what they consider hospitable conditions to metabolic activity return. We will consider the various biological states of individual organisms (active, inactive, transition) and how these states relate to the dynamic biological-physical-chemical context that makes up an organism's environment. Within these states the special adaptations of extremophiles and survivophiles have allowed life as a phenomenon to withstand global catastrophes, which include massive volcanic eruptions, supernovae explosions, and asteroid impacts. These are the catastrophes that changed the environments on Earth too quickly for organisms to adapt by Darwinian evolution. The genetic adaptations of extremophiles both allow them to thrive under at least some of the harsh conditions caused by catastrophes and these same adaptations make them a source of genetic information for intrinsically stable macromolecules. This genetic information for stable macromolecules can be shared with other organisms through lateral gene transfer. Similarly, the adaptations of survivophiles help insure that at least some representative of life will survival during global catastrophes. These organisms also provide a source of genes for bio-stabilizing molecules (e.g., heat shock proteins, trehalose and other organic solutes). We will discuss how the strategies and the specialized genes for growth and survival of extremophiles and survivophiles impact the continuity and perpetuity of life during the global catastrophes that have challenged life during its nearly 3.4 billion year residence on Earth.
November 29, 2005
Statistical Testing Of A Significant Radon-Earthquake Connection In The Dead Sea Rift
GIDEON STEINITZ
GEOLOGICAL SURVEY OF ISRAEL |
