Spatial and Genetic Relations of Coronae, Lobate Plains, and Rift Zones of Venus.

Based on the photogeological and stratigraphic analysis of Venusian coronae, we have found that (1) late manifestations of volcanic activity on Venus, lobate plains, are weakly related to the formation of coronae. The small number of coronae–sources of lobate plains (~17% of the total population of coronae) indicates that the volcanic activity of the coronae ceased mainly in the pre-Atlian time. Thus, the coronae associated with manifestations of late volcanism in the form of lobate plains are either long-lived volcano-tectonic complexes or structures of the final phases of volcanic activity; their locations mark the regions of long-term volcanism; (2) the small number of coronae formed by rift structures (~14% of the total population) indicates that rifting in the Atlian period did not lead to mass formation of coronae. The majority of Venusian coronae was probably formed in the Fortunian–Guineverian periods of the geological history of Venus. A sharp decrease in the number of coronae formed in the Atlian period may be associated with an increase in the thickness of the lithosphere and an increase in its role as a rheological barrier. [ABSTRACT FROM AUTHOR]