2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 307-3
Presentation Time: 9:00 AM-6:30 PM


GOOSMANN, Erik A.1, BUCZKOWSKI, Debra L.2, ERNST, Carolyn M.2, DENEVI, Brett W.2 and KINCZYK, Mallory J.2, (1)Colorado College, Colorado Springs, CO 80946, (2)Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, Erik.Goosmann@coloradocollege.edu

The largest impact basin on Mercury, the 1,550km diameter Caloris basin, is a highly complex geologic landform. The basin is floored by a spectrally distinct, high-reflectance volcanic plains unit emplaced post-impact, that covers a low-reflectance impact melt unit at least 7.5-8.5km thick [1]. In addition, several spectrally distinct pyroclastic vents have been identified within the basin [2]. Surrounding the basin are various ejecta units, which include the Odin Formation, a knobby plains unit that is stratigraphically and morphologically consistent as being Caloris ejecta but has the lowest crater size-frequency of any of the units associated with Caloris emplacement [3]. While the knobs are thought to be Caloris ejecta blocks, the dark, smooth volcanic plains interfingering them have been interpreted to be younger than those flooring Caloris, implying a second plains emplacement event possibly involving lower albedo volcanic material. In addition, the Odin Formation shows two distinct sub-units. The bright sub-unit, which contains fewer and fresher craters, might represent a younger volcanic flow while the dark sub-unit, which has a higher concentration of knobs, might represent Caloris ejecta. Geologic maps are useful tools in compiling geologic data into a single, accessible data source. Previous work by Mariner 10 geologic mappers covered roughly 1/3 of the basin, leaving 2/3 of the basin unmapped. We created a high-resolution geologic map of the Caloris basin using recently acquired MESSENGER data, with the goal of synthesizing the results of these previous studies into a contextual framework for ease of access. If possible, we plan on integrating our detailed Caloris map into the Mercury global geologic map currently under construction.

References: [1] Ernst et al. (2015) Icarus, 250, 413-429. [2] Goudge (2014) J. Geophys. Res. Planets, 119, 635-658. [3] Denevi et al. (2013) JGR, 118, doi:10.1002/jgre.20075.