megaregolith

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megaregolith The fractured and brecciated zone of rock formed on the lunar highland crust due to the intense early bombardment during the period from 4.4 billion years ago, when the crust was forming, to 3.85 billion years ago, when the Imbrium and Orientale collisions marked the close of the massive basin-forming events. Estimates of the depth of the megaregolith extend from 1 km to 25 km, the latter estimate coinciding with an observed seismic boundary.