Paper No. 7
Presentation Time: 9:00 AM-6:00 PM
GEOLOGIC AND STRUCTURAL MAPPING OF SOUTH TELLUS REGIO, VENUS: IMPLICATIONS FOR CRUSTAL PLATEAU EVOLUTION
GRAUPNER, Melanie, Department of Geological Sciences, University of Minnesota Duluth, 1114 Kirby Drive, 229HH, Duluth, MN 55812 and HANSEN, Vicki L., Department of Earth and Environmental Sciences, University of Minnesota Duluth, Duluth, MN 55812, graup044@d.umn.edu
NASA’s Magellan mission collected global data sets that allow geologic mapping of Venus with the goal of determining geologic histories and processes. In an effort to understand the formation of Tellus Regio (an ~2x10
6 km
2 crustal plateau centered at 43N/77E) geologic and structural mapping of southern Tellus (43N to 26N) is underway. Preliminary mapping reveals several suites of folds and extensional structures (ribbons and graben), and local basin fill. Fold wavelengths include small (<1 km; effective data resolution) and larger wavelengths (<12 km; typical range 8-12 km). All wavelengths are consistently distributed throughout Tellus, defining a fluid-like pattern lacking sharply demarked domain boundaries. Extensional structures, which typically trend orthogonal to fold crests, include shear fracture ribbons (1:25 aspect ratio) and graben complexes (1:3.5) with wavelengths of 2.5 and 30 km, respectively. Ribbon structures typically crosscut small wavelength folds; graben complexes dissect longer wavelength folds.
Structural basins (including fold and ribbons troughs, and graben complexes) show local flooding/fill, likely by volcanic flows. Flooded basins are distributed across the plateau. Some basins lack post-flooding deformation, whereas others show reactivated and imposed structures. The presence of local basin fill at all structural wavelengths indicates that layer contraction and extension occurred broadly synchronously with one another and with flooding.
Structural wavelength is related in part to layer thickness, which, in the case of Tellus, increased with time, with subsequent amplification of both contractional and extensional structures. Strain became more partitioned and more widely spaced with time, consistent with an increase in mechanical layer thickness. Through out this time, lava locally leaked to structural basins. The surface evolution (deformation and flooding) point to an extremely high geothermal gradient across all of Tellus Regio. With time cooling led to increased layer thickness, yet the surface retained mobility. The size of the area, the coherent pattern of extensional and contractional structures and flooding over the area is consistent with the lava pond hypothesis of crustal plateau evolution.
