A Stratigraphic Study of Small Volcano Clusters on Venus

The history of tectonism on Venus: A stratigraphic analysis

“…Shield plains are quite abundant on Venus and their exposed area comprises $ 18.5% of the surface of Venus (Table 1). The age relationships between individual shields and the surrounding materials are often ambiguous (Addington, 2001) and suggest that formation of the shields and intershield plains were overlapping in time. In contrast, the stratigraphic relationships of the unit of shield plains (both the shields and intershield plains) with the surrounding plains units are more clear and suggest that shield plains pre-date emplacement of regional plains (Ivanov and Head, 2004b).…”

Geologic map of the Themis Regio quadrangle (V-53), Venus

“…Instead, they may be basaltic in composition and have early-stage crusts that were either annealed or entrained to form the final, relatively smooth upper dome surfaces (Stofan and others, 2000). Edifice field material consists of clusters of small edifices that have associated lava flows and outcrops ranging in size from ~100 to 400 km across (Head and others, 1992;Guest and others, 1992;Addington, 2001). The unit is mapped on the basis that the edifices share a common source and (or) are stratigraphically related.…”

Geologic map of the Hecate Chasma quadrangle (V-28), Venus

“…4). To determine the relative ages of small edifices within the unit, we looked for crosscutting relations with secondary structures and superposition relations, similar to the method of Ivanov and Head (2004) (their criteria 1-3, 9, 10-12), and Addington (2001). However, Ivanov and Head (2004) relate ages of edifice fields to a unit 'regional plains with wrinkle ridges', which is not present in this quadrangle.…”