Investigation of target property effects on crater populations in long lava flows: A study in the Cerberus region, Mars, with implications for magma source identification

Abstract

Young volcanism on Mars is exemplified within the Cerberus region, which enables examination of relatively pristine lava flow surfaces. In this investigation, we derived model ages within the circum-Cerberus channelized lavas for sites proximal, medial, and distal to the lava flow sources, finding that these ages decrease with increasing distance from the inferred source. Investigating multiple possible explanations for this downstream decrease in model ages, we conclude that the most likely cause is changes in the rheological properties of the lava during emplacement. Analogous terrestrial lava flows exhibit rheological changes along their length during emplacement, supporting the hypothesis that target properties affect crater size frequency distributions (CSFDs) on extraterrestrial bodies. Using scaling methods, we investigated how possible material property changes in the Cerberus channelized lavas affected CSFDs. To derive a single model age for each channel, we arithmetically size-scaled the distal and proximal crater sizes. We also used pi-group scaling to estimate the effect of material strength and porosity on the final CSFDs. We infer that the Athabasca, Grjótá, and Marte Valles lavas underwent minor, moderate, and major rheological changes, respectively, to account for the progressively larger age discrepancies along their respective flow lengths. The arithmetic size-scaling yields relative lava emplacement ages, from oldest to youngest, respectively, as Grjótá, Marte, and Athabasca. This lack of a consistent progressive directional emplacement (east-to-west or west-to-east) of lava model ages implies that the magma source was spatially distributed beneath the Cerberus region, although magma contributions from the two bordering volcanic provinces cannot be ruled out. The results of this study support the findings of previous lunar and martian studies that inferred target property changes affected CSFDs, which may have some bearing on age dating of young lava surfaces across the inner Solar System.