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Published August 2018 | Accepted Version
Journal Article Open

Ring faults and ring dikes around the Orientale basin on the Moon

Abstract

The Orientale basin is the youngest and best-preserved multiring impact basin on the Moon, having experienced only modest modification by subsequent impacts and volcanism. Orientale is often treated as the type example of a multiring basin, with three prominent rings outside of the inner depression: the Inner Rook Montes, the Outer Rook Montes, and the Cordillera. Here we use gravity data from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission to reveal the subsurface structure of Orientale and its ring system. Gradients of the gravity data reveal a continuous ring dike intruded into the Outer Rook along the plane of the fault associated with the ring scarp. The volume of this ring dike is ∼18 times greater than the volume of all extrusive mare deposits associated with the basin. The gravity gradient signature of the Cordillera ring indicates an offset along the fault across a shallow density interface, interpreted to be the base of the low-density ejecta blanket. Both gravity gradients and crustal thickness models indicate that the edge of the central cavity is shifted inward relative to the equivalent Inner Rook ring at the surface. Models of the deep basin structure show inflections along the crust–mantle interface at both the Outer Rook and Cordillera rings, indicating that the basin ring faults extend from the surface to at least the base of the crust. Fault dips range from 13° to 22° for the Cordillera fault in the northeastern quadrant, to 90° for the Outer Rook in the northwestern quadrant. The fault dips for both outer rings are lowest in the northeast, possibly due to the effects of either the direction of projectile motion or regional gradients in pre-impact crustal thickness. Similar ring dikes and ring faults are observed around the majority of lunar basins.

Additional Information

© 2017 Published by Elsevier. Received 10 August 2017, Revised 17 November 2017, Accepted 7 December 2017, Available online 9 December 2017. This work was supported by Grant NNX16AT32G from the NASA GRAIL Guest Scientist Program and Grant NNX17AK53G from the NASA Lunar Data Analysis program to JCAH. BCJ was supported by Grant 80NSSC17K0341 from the NASA Lunar Data Analysis Program. We are grateful to Amanda Nahm and an anonymous reviewer for their helpful and insightful comments.

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Created:
August 19, 2023
Modified:
October 17, 2023