Lunar Wrinkle Ridges and the Evolution of the Nearside Lithosphere

Wrinkle ridges are the largest and most morphologically complex contractional landforms found on the Moon. They occur exclusively in mare basalt and are thought to result from load induced subsidence and flexure of the lunar lithosphere. The displacement-length (D-max/L) relations of wrinkle ridge thrust faults in mascons, where mare basalts are generally thickest, and non-mascon settings are compared. The results show no statistically significant difference in the population gamma values of the wrinkle ridges. D-max/L values of ridge faults are distributed over the entire range of the sampled population regardless of setting. This suggests that the elastic lithosphere supporting the nearside mare accommodated comparable ridge formation in non-mascons, with generally thinner sequences of load inducing mare basalt, to mascons. Analysis of the heat flow suggests the elastic lithosphere supporting non-mascons may have been relatively thin when wrinkle ridge formation began, possibly accounting for the similarity in D-max/L values with ridges in mascons. Thickening of the elastic lithosphere over time is expected to result in a progression in age of wrinkle ridges in mascon and non-mascon from oldest near mare centers to younger at the margins.