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Stratigraphy of the Caloris Basin, Mercury: Implications for Volcanic History and Basin Impact MeltCaloris basin, Mercury's youngest large impact basin, is filled by volcanic plains that are spectrally distinct from surrounding material. Post-plains impact craters of a variety of sizes populate the basin interior, and the spectra of the material they have excavated enable the thickness of the volcanic fill to be estimated and reveal the nature of the subsurface. The thickness of the interior volcanic plains is consistently at least 2.5 km, reaching 3.5 km in places, with thinner fill toward the edge of the basin. No systematic variations in fill thickness are observed with long-wavelength topography or azimuth. The lack of correlation between plains thickness and variations in elevation at large horizontal scales within the basin indicates that plains emplacement must have predated most, if not all, of the changes in long-wavelength topography that affected the basin. There are no embayed or unambiguously buried (ghost) craters with diameters greater than 10 km in the Caloris interior plains. The absence of such ghost craters indicates that one or more of the following scenarios must hold: the plains are sufficiently thick to have buried all evidence of craters that formed between the Caloris impact event and the emplacement of the plains; the plains were emplaced soon after basin formation; or the complex tectonic deformation of the basin interior has disguised wrinkle-ridge rings localized by buried craters. That low-reflectance material (LRM) was exposed by every impact that penetrated through the surface volcanic plains provides a means to explore near-surface stratigraphy. If all occurrences of LRM are derived from a single layer, the subsurface LRM deposit is at least 7.5-8.5 km thick and its top likely once made up the Caloris basin floor. The Caloris-forming impact would have generated a layer of impact melt 3-15 km thick; such a layer could account for the entire thickness of LRM. This material would have been derived from a combination of lower crust and upper mantle.
Document ID
20160008399
Document Type
Reprint (Version printed in journal)
Authors
Ernst, Carolyn M. (Johns Hopkins Univ. Laurel, MD, United States)
Denevi, Brett W. (Johns Hopkins Univ. Laurel, MD, United States)
Barnouin, Olivier S. (Johns Hopkins Univ. Laurel, MD, United States)
Klimczak, Christian (Carnegie Institution of Washington Washington, DC, United States)
Chabot, Nancy L. (Johns Hopkins Univ. Laurel, MD, United States)
Head, James W. (Brown Univ. Providence, RI, United States)
Murchie, Scott L. (Johns Hopkins Univ. Laurel, MD, United States)
Neumann, Gregory A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Prockter, Louis M. (Johns Hopkins Univ. Laurel, MD, United States)
Robinson, Mark S. (Arizona State Univ. Tempe, AZ, United States)
Solomon, Sean C. (Carnegie Institution of Washington Washington, DC, United States)
Watters, Thomas R. (Smithsonian Institution Washington, DC, United States)
Date Acquired
July 1, 2016
Publication Date
April 1, 2015
Publication Information
Publication: Icarus
Volume: 250
ISSN: 0019-1035
Subject Category
Geosciences (General)
Report/Patent Number
GSFC-E-DAA-TN20613
Funding Number(s)
CONTRACT_GRANT: NAS5-97271
CONTRACT_GRANT: NASW-00002
Distribution Limits
Public
Copyright
Other
Keywords
Cratering
volcanism
Mercury