Explosive volcanism in the Tharsis region: Global evidence in the martian geologic record
B. M. Hynek, R. J. Phillips, R. E. Arvidson 2003 Journal of Geophysical Research V108 no.E9 5111, doi:10.1029/2003JE002062
This article from the Geophysical Research Journal re-examines a global equatorial set of massive to finely layered stacks of material on Mars. The authors conclude that these friable layered deposits are not lacustrine in origin, but are consistent with an episodic, subareal source. Thinning of deposits with distance from the Tharsis rise suggest that the material may be composed of volcanic tephra from past explosive eruptions in the Tharsis region.
