CONSTRUCTION AND EVOLUTION OF AN ICE-CONFINED BASALTIC ERUPTIVE FISSURE COMPLEX: A PLANETARY PERSPECTIVE

Deposits from formerly ice-confined fissure-fed basaltic eruptions are common in Iceland, and similar linear, dike-fed, steep-sided edifices on Mars have been interpreted to have a similar origin (i.e., phreatomagmatic explosions generated by dike-cryosphere interactions). In Iceland, these dikes occur in swarms and create complexes of closely spaced, sub-parallel, and multi-vent ridges. Individual ridges are constructed mostly of numerous, linked, regularly-spaced and steep-sided topographic highs (point-source vents) and short ridges (fissure vents) of subaqueous lavas, most of which are draped by phreatomagmatic tephra. There are more than 1000 such ridges in Iceland, and they represent an important and largely untapped database of North Atlantic terrestrial paleo-ice conditions. They also serve as likely terrestrial analogs for similar dike-fed structures on Mars, such as that described near the source of the Mangala Valles outflow channel. In southwest Iceland, Sveifluháls is a 21.5 km-long, formerly ice-confined fissure complex that was erupted during the Last Glacial Maximum. Ice-thickness estimates, based on volatile analysis of pillow rind glass, vary from 70-400 m. This is the first detailed study of such a complex that is mainly focused on how it was constructed in space and time. Particularly, this research examines how the ridge complex differs from published studies of simple single short fissure ice-confined centers, how it interacted with the overlying ice, and how it recorded paleo-ice conditions and eruptive environments. We present here our data describing vent locations, eruption product volumes, volumes of ice melted, and locations of possible meltwater pathways. We discuss the most important differences of the processes and products of such ridge complexes in comparison to published examples of short ”monogenetic” ridges on Earth. We also discuss the implication of these differences for modeling ice melting and meltwater drainage, and compare our results with the postulated Martian examples.