Ongoing Projects
Cenozoic basins in central Tibet: a record of out-of-sequence tectonics and lithospheric dripping after onset of continental collision?
Orogenic plateaus, like orogenic wedges, are first-order features of convergent margins common to both accretionary subduction systems and collisional continental orogens. Though the geometry and deformation of orogenic wedges are well-described by critical taper theory, no consensus model accounts for the complexities of how broad plateaus are elevated and maintained. A primary reason is that, while mass-balance in orogenic wedges is limited to the crustal section, mass-balance in orogenic plateaus is challenging because it involves the entire lithospheric column. Besides arc processes (magmatic accretion and removal of arclogite), mass-balance in plateaus must account for (+) underthrusting, relamination, or underplating, and (-) erosion, lower crustal extrusion, or large-scale lithospheric delamination or smaller-scale dripping. The lower lithosphere remains a blindspot in our knowledge of plateaus.
In the Himalayan-Tibet orogen, estimated upper-crustal shortening is thought to imply > 14 million cubic km of underthrust mantle lithosphere and lower crust material that must be accounted for. Where did all of it go? Characterizing the extent, timing, and nature of lithospheric removal beneath plateaus is the missing link in our understanding of the whole system, but it is also particularly difficult to investigate, because it is a transient process where the evidence quite literally sinks away. Our approach is to take the only thing we have—the surface geologic record—and see what it might tell us about the critical post-collisional period after initiation of hard collision of the continents. The current focus of the project is a newly discovered Eocene basin in Central Tibet (Qiangtang), which might contain clues to what's happening at depth. This involves detailed geologic mapping, U-Pb detrital and igneous zircon geochronology, structural mapping of intrabasinal deformation, along with measurement of stratigraphic sections, lithological and facies descriptions, interpretation depositional process and paleoenvironment interpretations, and basin analysis. We also are looking into the exhumation (low-temperature thermochronology) and magmatic record.
Orogenic plateaus, like orogenic wedges, are first-order features of convergent margins common to both accretionary subduction systems and collisional continental orogens. Though the geometry and deformation of orogenic wedges are well-described by critical taper theory, no consensus model accounts for the complexities of how broad plateaus are elevated and maintained. A primary reason is that, while mass-balance in orogenic wedges is limited to the crustal section, mass-balance in orogenic plateaus is challenging because it involves the entire lithospheric column. Besides arc processes (magmatic accretion and removal of arclogite), mass-balance in plateaus must account for (+) underthrusting, relamination, or underplating, and (-) erosion, lower crustal extrusion, or large-scale lithospheric delamination or smaller-scale dripping. The lower lithosphere remains a blindspot in our knowledge of plateaus.
In the Himalayan-Tibet orogen, estimated upper-crustal shortening is thought to imply > 14 million cubic km of underthrust mantle lithosphere and lower crust material that must be accounted for. Where did all of it go? Characterizing the extent, timing, and nature of lithospheric removal beneath plateaus is the missing link in our understanding of the whole system, but it is also particularly difficult to investigate, because it is a transient process where the evidence quite literally sinks away. Our approach is to take the only thing we have—the surface geologic record—and see what it might tell us about the critical post-collisional period after initiation of hard collision of the continents. The current focus of the project is a newly discovered Eocene basin in Central Tibet (Qiangtang), which might contain clues to what's happening at depth. This involves detailed geologic mapping, U-Pb detrital and igneous zircon geochronology, structural mapping of intrabasinal deformation, along with measurement of stratigraphic sections, lithological and facies descriptions, interpretation depositional process and paleoenvironment interpretations, and basin analysis. We also are looking into the exhumation (low-temperature thermochronology) and magmatic record.
Past Projects
