Outflow channels with deltaic deposits in Ismenius Lacus, Mars

Research areas:
Year:
2013
Authors:
Journal:
ICARUS
Volume:
226
Number:
1
Pages:
385-401
Month:
SEP-OCT
ISSN:
0019-1035
Abstract:
A connected series of outflow channels in the Ismenius Lacus quadrangle
are identified for the first time and characterized using High
Resolution Stereo Camera images of Mars Express, the Context camera
images of Mars Reconnaissance Orbiter and the topography of the Mars
Observer Laser Altimeter. These channels (named Okavango Valles), which
stretch over >400 km south to north and join the northern plains, were
identified from braided channels, scour/groove marks, poorly sinuous
valleys and depositional landforms. Discharge rates were estimated to
0.1-5 x 10(6) m(3) s(-1) from analysis of the topography of scour marks.
Pathways of channels segments were extracted from topography showing a
unique source at a breached crater rim, suggesting overflow from ponded
depressions. A series of delta fans are observed inside depressions
along the channel pathways. The presence of these deltas formed in
former bodies of water is a compelling argument for formation of this
outflow channel system by fluvial flows. The similarity of these flows
with other outflow channels on Mars proves that volcanically-related
outflows cannot explain all such features. In addition, this study also
shows that catastrophic floods are able to create fan deltas in
transient lakes. This example has to be taken into account in the
interpretation of late stage fans associated with poorly branched
valleys and single channels. (C) 2013 Elsevier Inc. All rights reserved.