Is surface geology linked to mantle structure beneath ancient orogens? New insights from the New England Seismic Transect (NEST)

Laura’s research combines field work with (micro)structural and geochronological analyses to study tectonic histories and processes. Much of her work has been conducted internationally in remote regions of Mongolia and Papua New Guinea. Her EPS seminar will highlight current NSF-funded collaborative research much closer to home where she and colleagues from Williams College and Yale University are working together on the NEST project (New England Seismic Transect), in which data from passive seismic broadband arrays (NEST, SEISConn) have been used to image lithospheric structure. A major geophysical finding is that the Moho step previously imaged using EarthScope data and interpreted to represent the suture between Laurentia and accreted Appalachian terranes is, rather, a Moho overthrust. New geologic evidence from the western Appalachian front documents reverse motion at ca. 420 Ma along faults that roughly coincide with a projected surface trace of the Moho overthrust. The reverse faults cut thrust faults from the Ordovician Taconic Orogeny and place Laurentian basement over its sedimentary cover sequences. Many of the faults record (micro)structural and geochronological evidence for polyphase deformation. Are these faults related to the Moho overthrust? Data from newly added NEST seismic node arrays will help image the crust in our quest to test links between the surface geology and mantle structure.

Speaker: Laura Webb, University of Vermont