Continual geological activity in Athabasca Valles, Mars

[1] Comprehensive studies of the stratigraphic relationships in the Athabasca Valles region have been performed on imagery from the Viking Orbiters and the Mars Orbiter Camera ( narrow and wide angle) on board Mars Global Surveyor as well as by making use of topographic data derived from the Mars Global Surveyor Laser Altimeter (MOLA) instrument. From superimposed crater frequencies we have derived absolute surface ages by applying the Hartmann and Neukum [2001] cratering chronology model. The main channel has been incised into the Cerberus volcanic plains with an average plains age of 3.4 Ga. The main fluvial or glacial erosion processes ended 2.6 Ga ago. This result shows that the age of the valley system itself is older than commonly believed. One major possible fluvial event occurred in the topographically lower volcanic plains southwest of the valley 1.6 Ga ago. The valley itself was covered by lava episodically and ending 0.9 Ga and in case of a few younger episodes 30 Ma ago. The surface texture south of the valley system suggests a younger, possibly fluvial overprinting of the volcanic texture 30 Ma ago. The latest volcanic activity is dated to about 3 Ma ago. With the latter ages we have been able not only to confirm earlier age estimates by Berman and Hartmann [ 2002] but also to show that the valley system itself has undergone over a period of two billion years active geological cycles which were dominated by volcanic processes at the end.