Exploring the Volcanic History of the Crisium Basin through Geologic Mapping

Motivation: Volcanism has played an important role in the evolution of the Moon’s crust, largely through the emplacement of basaltic flows. The coalescence of these flows formed the vast plains that make up the lunar mare, though their distribution across the Moon’s surface is highly concentrated on the nearside within a geochemically distinct region termed the Procellarum KREEP Terrane (PKT). The prevailing explanation for the dramatic asymmetry exhibited by lunar volcanism is that the PKT represents the manifestation of a unique lunar province that is host to a shallow reservoir of heat producing elements. But is the story more complex than this?

Approach and Implications: To further explore whether the diversity and duration of lunar volcanism can be neatly defined by its geochemical province, we propose a detailed geological mapping based investigation of the volcanic history of the Crisium basin,
a prominent volcanic region that is situated well outside of the PKT. We propose to produce a comprehensive geologic map of the Crisium region to explore the full range of volcanic products present in terms of composition, eruptive style, and relative and absolute timing of eruptions, which we will then compare to the many studies of volcanic regions within the PKT to establish whether clear distinctions arise that would further support the two-province model of lunar volcanism. Alternatively, if we find Crisium hosts a long-duration and diverse assortment of volcanic deposits, it would provide an important reference point to assessing the role of the PKT in lunar volcanic history and the broader thermal evolution of the Moon.

Relevance: The objectives of the proposed research are relevant to LDAP, which supports research that enhance the scientific return of lunar missions through the use of mission data. The proposed research will analyze PDS mission data from multiple instruments to undertake scientific investigations and produce a USGS geologic map. The research is pertinent to multiple Volcanology goals in the Lunar EAG Advancing Science of the Moon Specific Action Team Lunar Exploration Analysis Group Final Report [2018], which are to determine (3b) the variety, age, distribution, and origin of lunar rock types, (5a) the origin and variability of lunar basalts and (5d) the flux of lunar volcanism and its evolution through space and time. We intend to publish this geologic map through the USGS where it will be made available to the public, as well as a second publication summarizing the volcanic history of the region as it relates to the FHT, PKT, and lunar volcanic and thermal evolution.