A field investigation of the basaltic ring structures of the Channeled Scabland and the relevance to Mars

Geomorphology
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Abstract

The basaltic ring structure (BRS) is a class of peculiar features only reported in the Channeled Scabland of eastern Washington State. They have been suggested to be good analogs, however, for some circular features on Mars. BRSs are found where Pleistocene floods scoured the Columbia River Basin, stripping off the uppermost part of the Miocene Columbia River Basalt Group and exposing structures that were previously embedded in the lava. The “Odessa Craters,” near Odessa, WA, are 50–500-m-wide BRSs that are comprised of discontinuous, concentric outcrops of subvertically-jointed basalt and autointrusive dikes. Detailed field investigation of the Odessa Craters in planform and a cross-sectional exposure of a similar structure above Banks Lake, WA, lead us to propose that BRSs formed by concurrent phreatovolcanism and lava flow inflation. In this model, phreatovolcanic (a.k.a., “rootless”) cones formed on a relatively thin, active lava flow; the lava flow inflated around the cones, locally inverting topography; tensile stresses caused concentric fracturing of the lava crust; lava from within the molten interior of the flow exploited the fractures and buried the phreatovolcanic cones; and subsequent erosive floods excavated the structures. Another population of BRSs near Tokio Station, WA, consists of single-ringed, raised-rimmed structures that are smaller and more randomly distributed than the Odessa Craters. We find evidence for a phreatovolcanic component to the origin as well, and hypothesize that they are either flood-eroded phreatovolcanic cones or Odessa Crater-like BRSs. This work indicates that BRSs are not good analogs to the features on Mars because the martian features are found on the uneroded surfaces. Despite this, the now superseded concepts for BRS formation are useful for understanding the formation of the martian features.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A field investigation of the basaltic ring structures of the Channeled Scabland and the relevance to Mars
Series title Geomorphology
DOI 10.1016/j.geomorph.2014.06.027
Volume 240
Year Published 2015
Language English
Publisher Elsevier
Contributing office(s) Astrogeology Science Center
Description 10 p.
First page 34
Last page 43
Conference Title 45th Annual Binghamton Geomorphology Symposium
Conference Location Knoxville, TN
Conference Date September 12-14, 2014
Country United States
State Washington
Other Geospatial Channeled Scabland, Mars, Odessa Craters
Online Only (Y/N) N
Additional Online Files (Y/N) N