Western Fortuna Tessera, Ishtar Terra, records polyphase deformation. Structures include: ribbons forming long, narrow, steep-sided troughs that reflect surface layer extension; N-trending folds related to Maxwell Montes deformation; short, wide, NW-trending graben that reflect late local extension; and, within the southwestern map area, gentle, E-trending warps, which postdate ribbon structures. Flood lava flows postdate deformation. Ribbon structures change orientation radially from NNE to WNW. These observations caution against the correlation of Fortuna Tessera with tessera elsewhere on Venus and against the proposal that tessera forms a global stratigraphic layer.
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