The Circum-Hellas Volcanic Province, Mars: Assessment of wrinkle-ridged plains

Wrinkle-ridged plains, common on the terrestrial planets, are inferred to form by tectonic deformation of volcanic or sedimentary surfaces. If wrinkle-ridged plains adjacent to volcanic features originated from volcanic activity associated with the features, then the plains should have similar ages to the volcanic features, as well as other morphological or compositional indicators of volcanism. We test this hypothesis on several regions of wrinkle-ridged plains bounding the Circum-Hellas Volcanic Province (CHVP). We constructed THEMIS daytime-IR mosaics (spatial resolution 100 m/pixel) and performed crater counts to determined cratering model formation ages of these regions. We found ages of 3.4–3.7 Ga for SE Malea Planum, 3.6–3.7 Ga for W Promethei Terra, 3.5–3.7 Ga for Hesperia Planum, and 3.6–3.8 Ga for the eastern Hellas basin floor, all of which are contemporaneous with the formation of the major volcanic edifices (3.6–3.8 Ga) in the CHVP. Although examination of available MOC, CTX, HiRISE, THEMIS, and HRSC data shows few examples of features definitive of a volcanic origin of these wrinkle-ridged plains, HRSC true color images (50–100 m/pixel) show that large areas of these plains have a dark blue–black color, consistent with previous Viking and Mars Express HRSC and OMEGA color-spectral studies indicative of basaltic compositions. However, in some areas this color may be due to aeolian mantles rather than underlying bedrock. Thus, we cannot demonstrate unequivocally that these wrinkle-ridged plains are volcanic, beyond the synchronicity of their formation ages with those of the CHVP volcanoes. Nevertheless, if these wrinkle-ridged plains were originally formed by volcanic activity, or other processes induced by volcanic activity, then the inclusion of these regions brings the size of the CHVP to > 4.86 × 106 km2, comparable in size to the Elysium volcanic province. Thus, the CHVP may have been a dominant source of volcanism early in Martian history.