On the formation of thrust fault-related landforms in Mercury’s Northern
Smooth Plains: A new mechanical model of the lithosphere
Abstract
There are a large number of tectonic shortening structures distributed
across the planet Mercury, which are interpreted as the product of
lithospheric deformation mainly attribute to secular cooling of the
planetary interior. As the largest single volcanic deposit on Mercury,
the northern smooth plains (NSP) is dominated by thrust fault-related
landforms, showing particularity in their geomorphic features and
requires an assumed weak layer at a shallow depth to account for the
thin-rooted deformation in the lithosphere. However, there is a lack of
proper mechanical model to account for such layer in the lithosphere
beneath the NSP. In this work, we propose a new mechanical model
allowing for a mechanically discontinuous lithosphere by introducing the
semi-brittle deformation style, with detailed model configurations. Our
work simulates a compressive dynamic process to mimic the formation for
thrust fault-related landforms in the NSP of 3.8 billion years ago
through 2-D numerical simulations. This simulation lasts for 70 million
years, resulting in a concentrated and high strain rate region (i.e.,
weak layer) at shallow depth in the crust and geomorphically consistent
surface topography with commonly observed thrust fault-related
landforms. Geomorphically steady surface relief suggests that these
shortening landforms were formed in a short period of time on geological
time scales, and have maintained their basic geomorphic features to
present day. The potential influence of the topography at the
crust-mantle boundary on the surface relief is also recognized.
Additional set of numerical simulations emphasizes that a larger
topography facilitates the formation for higher surface relief.