Impact craters on regional plains on Venus: Age relations with wrinkle ridges and implications for the geological evolution of Venus

[1] A global assessment of impact craters on Venus 30 km in diameter shows that 146 craters are completely or partially superposed on the regional plains that dominate the surface and typically are deformed by wrinkle ridges. In this study, we found that 10 of these craters are deformed by wrinkle ridges (pre-WR), 93 craters are superposed on wrinkle ridges (post-WR), and 43 craters were found to be ambiguous cases. We compared our findings with the results of a similar study by McGill (2004) done for craters of all sizes but for 1/3 of the surface of Venus. We found that the percentage of pre-WR craters found by McGill (2004) among the unambiguous cases (15%) is close to our percentage (10%), but we are in disagreement on the classification of a significant number of specific craters and in this analysis we describe the major reason for the disagreements. We then summarize published data on the crater densities for different plains on Venus. We assess Monte Carlo modeling of volcanic resurfacing, which competed with the ongoing formation of impact craters. On the basis of these data and analyses, we conclude that the mean age of the regional plains is close to the mean global surface age of Venus and that the potential time span of regional plains emplacement was relatively short. We interpret our results as evidence that wrinkle ridging on Venus was a distinct tectonic phase that occurred rather early in post-regional-plains time, probably within the first 10%. Although the exact duration remains uncertain, regional and global stratigraphic relationships strongly support the hypothesis that wrinkle ridging on Venus predominantly occurred during a specific phase of history. The geologic record of wrinkle ridging and post-plains tectonic evolution of volcanic plains on the Moon and Mars show interesting similarities to those of Venus.