SIEDCAR (Seismic Investigation of Edge driven Convection Associated with the Rio Grande Rift) is a 2D array of 75 broadband seismographs deployed along the western edge of the Great Plains. SIEDCAR was designed to determine whether small-scale, edge-driven convection is occurring along the edge of the Great Plains, east of the Rio Grande rift zone, and if so, what its lateral dimensions are. The SIEDCAR proposal did not include a request for funding for a geodynamic modeling component to address its two other questions: 1) what conditions lead to edge-driven convection, and 2) what (if any) are tectonic (surface) effects of edge-driven convection and how do they match geologic observations. Although no funding was requested for the Geodynamic Modeling, it was considered a critical component of the SIEDCAR proposal by the PI?s, by the reviewers, and by the Program Officer. The present proposal serves to pursue funding for the geodynamic modeling component of SIEDCAR, and was developed in collaboration with SIEDCAR PIs Pulliam and Grand.
Numerical experiments show that an abrupt change in the thickness of the lithosphere can have a profound effect on upper mantle flow. There is a downwelling at the lithospheric discontinuity, and upwelling below the thinner lithosphere. Whether such small-scale convective flow (edge-driven convection) in the mantle is a significant, real world phenomenon and, if so, what the effects on surface geology are, is unknown. SIEDCAR will provide tomographic images of the upper mantle along the edge of the Great Plains, where edge-driven convection supposedly occurs.
Our goal of this proposal is to answer the following questions: 1) Regarding the process of edge-driven convection: When does edge-driven convection occur? What rheological or other parameters influence this process? How does edge-driven convection look like in 3D? Which part of the lithosphere may detach and sink into the asthenosphere (only mantle lithosphere or also lower crust?) What are surface effects? Where (if any) is partial melting expected? 2) Regarding the fast-velocity structure imaged by SIEDCAR: Is this fast-velocity structure related to edge driven convection? What is the nature of the fast-velocity anomaly? 3) Regarding crustal and surface effects: How does edge-driven convection relate to tectonics, surface processes (vertical movements), and volcanism in southeastern New Mexico?
We will use the numerical software Citcom for a Geodynamic Modeling study of edge-driven convection. In addition, our PhD student will do waveform modeling to validate and calibrate the tomography produced previously. Our proposed research would overlap one year with SIEDCAR.
Ten High-school teachers have participated in SIEDCAR field and data analysis efforts and workshops. The SIEDCAR project includes a component that provides field and data analysis experiences for minority-serving teachers in Texas and New Mexico in collaboration with separate E&O projects that aim to increase diversity in the geosciences. By partnering with UT Austin's GeoFORCE Texas public/private consortium and the project entitled Strengthening Pathways to Diversity Through Professional Development for Minority-Serving K-12 Science Educators (funded by NSF's Opportunities for Enhancing Diversity in the Geosciences (OEDG) Program), we accessed the Texas Regional Collaboratives for Excellence in Science Education to recruit the high school teachers. The SIEDCAR project has assembled a strong cadre of teachers who are enthusiastic and engaged. We propose to extend the program by one more summer, in order to add a geodynamic component to the teacher workshops and to ensure that final products are finalized: organized and well-documented. We thus propose to conduct a single, ten-days workshop for ten teachers in year one of this project which follows up on a SIEDCAR workshop. These lessons will be well-organized, well-documented, and self-contained and will be broadly distributed to interested teachers. They will be performed in collaboration with the SIEDCAR PIs.
We developed geodynamic computer models of mantle lithosphere deformation and instabilities and related crustal deformation to study the origin and evolution of the fast velocity upper mantle structure that has been imaged below the western Great Plains/ southeastern Rio Grande rift. It is important to understand the upper mantle in this area for several reasons: upper mantle processes probably affected landscape evolution in southeastern New Mexico/western Texas; and the area is the location of the Permian Basin, an important petroleum production area. Understanding the tectonic history of the region helps us in understanding the petroleum system. We found that the origin of the material is not Great Plains cratonic, strong lithosphere, but rather material that has been removed from the North American plate base during flat slab subduction of the Farallon Plate. When this material was scraped off the base of the North American plate, it was moved eastward and resulted into Laramide deformation (and formation of the southern Rockies). The material was transported to the edge of the Great Plains, and is currently recognized in seismic material as fast velocity upper mantle. It has destabilized, and is now "dripping" into the mantle. Our models show how this material may destabilize, and what the consequences are for crustal deformation in the area. We developed geodynamic computer models of mantle lithosphere deformation and instabilities and related crustal deformation to study the origin and evolution of the fast velocity upper mantle structure that has been imaged below the western Great Plains/ southeastern Rio Grande rift. It is important to understand the upper mantle in this area for several reasons: upper mantle processes probably affected landscape evolution in southeastern New Mexico/western Texas; the area is the location of the Permian Basin, an important petroleum production area. Understanding the tectonic history of the region helps us in understanding the petroleum system. We found that the origin of the material is not Great Plains cratonic, strong lithosphere, but rather material that has been removed from the North American plate base during flat slab subduction of the Farallon Plate. When this material was scraped off the base of the North American plate, it was moved eastward and resulted into Laramide deformation (and formation of the southern Rockies). The material was transported to the edge of the Great Plains, and is currently recognized in seismic material as fast velocity upper mantle. It has destabilized, and is now "dripping" into the mantle. Our models show how this material may destabilize, and what the consequences are for crustal deformation in the area. We developed geodynamic computer models of mantle lithosphere deformation and instabilities and related crustal deformation to study the origin and evolution of the fast velocity upper mantle structure that has been imaged below the western Great Plains/ southeastern Rio Grande rift. It is important to understand the upper mantle in this area for several reasons: upper mantle processes probably affected landscape evolution in southeastern New Mexico/western Texas; the area is the location of the Permian Basin, an important petroleum production area. Understanding the tectonic history of the region helps us in understanding the petroleum system. We found that the origin of the material is not Great Plains cratonic, strong lithosphere, but rather material that has been removed from the North American plate base during flat slab subduction of the Farallon Plate. When this material was scraped off the base of the North American plate, it was moved eastward and resulted into Laramide deformation (and formation of the southern Rockies). The material was transported to the edge of the Great Plains, and is currently recognized in seismic material as fast velocity upper mantle. It has destabilized, and is now "dripping" into the mantle. Our models show how this material may destabilize, and what the consequences are for crustal deformation in the area.
