Embayed intermediate volcanoes on Venus: Implications for the evolution of the volcanic plains

Abstract

Volcanoes on Venus are classified according to size with studies on the stratigraphic position of large volcanoes proposing that most of the large volcanoes postdate the regional volcanic materials. Some studies regarding intermediate volcanoes proposed that some of these volcanic features could be large volcanoes with embayed flow aprons, a situation that would alter the previous stratigraphic considerations about large volcanoes on Venus. In this work I analyze the global population of embayed intermediate-size volcanoes and compare their summits with that of other edifices classified as large volcanoes. Intermediate-size volcanoes are considered embayed when: (1) flows from another source clearly overlap the volcano slopes, and (2) display scarps related to flank-failure processes but with the associated collapse deposits being absent (i.e. interpreted as covered). As result of the survey 88 embayed intermediate-size volcanoes have been catalogued and integrated into a Geographic Information System. These embayed volcanoes have summit sizes and characteristics similar to large volcanoes and, therefore, could be interpreted as possible large volcanoes with their flow aprons embayed. Embayment materials for these volcanoes include all the units present in the history of the volcanic plains and would indicate that this type of central volcanic edifice would occur throughout the geologic history recorded in the venusian plains.