A Wrinkly Crater

An unnamed crater deformed by tectonic forces. LROC NAC M183760209L, image width is 960 m [NASA/GSFC/Arizona State University].

Wrinkle ridges are one of the most common tectonic features on the Moon, and they are found in the lunar maria. Today's Featured Image focuses on one wrinkle ridge, designated Vitello R from the nearby crater, deforming a small mare crater located just south of Mare Humorum. We can tell the wrinkle ridge, and associated tectonic deformation, is much younger than the mare pond as it cross-cuts and modifies the crater (the crater formed after the mare was deposited). Crater counting indicates Mare Humorum is ~3.5 billion years old, but can we say anything more definite about the timing of this wrinkle ridge's formation? Looking at the entirety of the wrinkle ridge may give us more clues.

Context image of today's Featured Image (white arrow). The wrinkle ridge can be seen transitioning into a lobate scarp when it exits the mare pond (black arrows). Image width is 100 km [NASA/GSFC/Arizona State University].

The wrinkle ridge shows a peculiar change in morphology as it crosses from the mare to the nearby highlands. The wrinkle ridge transitions to a lobate scarp both in the north and south! While wrinkle ridges are characterized by a broad arch with smaller associated ridges, lobate scarps are generally asymmetric landforms with a steep scarp face and shallow tailing end. Both landforms are interpreted as the surface manifestation of thrust faulting in different tectonic settings, so the wrinkle ridge and lobate scarps are probably related. A fresh crater in the bottom-left of the context image erases a portion of the western lobate scarp, but everywhere else the scarp deforms the surface. We can then infer from these observations that the wrinkle ridge-lobate scarp is both caused by a single thrust fault and is fairly young!

Explore more of the wrinkle ridge in the full LROC NAC! 

Related Posts:
Not Your Average Scarp
Bulging Wrinkle
Tectonics in Mare Frigoris

Published by Drew Enns on 8 June 2012