Substantial Lateral Motions Accompany Tectonic Deformation on Venus

Absent plate tectonics, deformation accompanying large-scale relative horizontal motion of the lithosphere on Venus is much more evenly distributed than that on Earth, which is mainly concentrated at plate boundaries. Yet Earth's plates, especially those of the continental lithosphere, are themselves internally deformed, often in a spatially distributed manner. Tectonic deformation on Venus thus has parallels to intraplate deformation on Earth, and so the morphology and kinematics of large-scale tectonics on Venus can be compared with structurally similar intraplate regions here. For example, numerous low-lying plains on Venus delineated by fold belts are analogous to mountain-range-bound sedimentary basins on Earth. One such site, northeast of Artemis Corona, is elliptical in plan and, at 1100 km in east-west and 620 km in north-south dimension, is akin to the Tarim Basin in northwest China (1250 km × 560 km). The fold belts demarcating this plain structurally resemble the Tian Shan range to the northwest and the Altun Shan to the southeast of the Tarim Basin, as well as the southern mountain range of the Sichuan Basin in southwest China. Notably, the Sichuan Basin is comparable in size (560 km × 390 km) to two other elliptical, fold-belt-bordered plains in the northeastern portion of Lada Terra on Venus (400 km × 300 km and 400 km × 370 km, respectively). The mountain ranges that delimit both the Tarim and Sichuan basins have accommodated substantial transpressive deformation: the Altun Shan range is situated atop the major Altyn Tagh left-lateral strike-slip fault, and the Longmenshan thrust belt to the northwest of the Sichuan Basin includes right-lateral shear. The fold belts on Venus may therefore possess a greater component of transpressive deformation than currently recognized, and these structures may thereby have facilitated more large-scale lateral mobility of the planet's lithosphere than previously thought.