SEQUENCE OF TECTONIC DEFORMATION IN THE HISTORY OF VENUS - EVIDENCE FROM GLOBAL STRATIGRAPHIC RELATIONSHIPS

Analysis of local and regional stratigraphic relationships has permitt ed the assessment of the nature of tectonic structures and their distr ibution throughout the observed history of Venus, spanning the past se veral hundreds of millions of Sears, We find that shortening character istic of intensely deformed tessera terrain gave way to widespread dis tributed fracturing and extension within the tessera and early post-te ssera volcanic plains. This phase was followed by distributed deformat ion of the widespread younger volcanic plains involving compression to form broad ridge belts and closely following-and sometimes simultaneo us-extension to form fracture belts, Emplacement of the most areally e xtensive regional volcanic plains exposed today was followed by widely distributed compression forming wrinkle ridges on the plains' surface s, Focused extensional deformation (localized, linear rift systems) do minated the latest stages. These major temporal trends appear well est ablished from a stratigraphic point of view and provide guidelines and constraints on models for the geologic history of Venus.