Using Distributional Characteristics of Superposed Large-scale Crater Clusters as Temporal Indicators of Geologic

Introduction: Improving the temporal constraints of Martian geologic processes is essential for understanding the formational history of the planet and providing adequate context for exploration. Martian surfaces are generally delineated into discrete packages based on morphological, compositional, and/or temporal characteristics, the latter of which are derived through (1) apparent cross-cutting relationships between geologic units and tectonic features and (2) the size and density of impact craters of any given surface [e.g., 1]. Size-frequency distributions of impact craters on the Martian surface have long been used as a proxy for dating the age of Martian geologic units [1-3]. What have not been systematically applied to strati-graphic studies are large crater clusters (those ≥20 km in length and containing ≥10 individual craters ≥300 m in diameter [4]). Herein, we present progress toward a new method for refining the current Martian time-stratigraphic scheme by using publicly available global datasets and Geographic Information Systems (GIS) technologies. Rationale: Present workflows for the temporal subdivision of Martian geologic terrains are not straightforward, particularly when attempting to use full array of current dataset resolutions. Our method intends to establish a systematic and repeatable approach of stratigraphic studies that uses the spatial distribution and cross-cutting relationships of large crater clusters (LCCs). The goal is avoid many of the interpretive nuances that often plague stratigraphic analyses using crater density assessments. Martian surfaces are generally delineated through temporal characteristics that include crosscutting relationships of geologic units and the size and frequency of impact craters [1]. These two, along with other morphological and compositional properties are the basis for defining the boundaries of geologic events through time. This type of interpretive temporal-assessment is complex, because of the many characteristics that are taken into account when placing time constraints on the surfaces. Our new methodology, presented here, focuses on the identification and classification of LCCs as a means to provide stratigraphic markers. Our method uses the distributional characteristics of LCCs as a proxy for partitioning the current strati-graphic framework. To this end, we are required to find out if the clusters were formed (1) as primary impacts , via swarms of meteoroids that entered the at