Abstract
Pit craters are enigmatic, quasi-circular depressions observed on rocky
(e.g., Earth and Mars) and icy (e.g., Enceladus) planetary bodies, and
numerous asteroids. These depressions are not related to meteorite
impacts. Instead pit craters are thought to be generated by overburden
collapse into a subsurface cavity (e.g., created by dilatational
faulting), or volumetrically depleted zone (e.g., an evacuated magma
reservoir or conduit). The surface size and distribution of pit craters
should thus provide an important record of otherwise inaccessible
subsurface processes. Because we cannot access the subsurface structure
of pit craters observed on planetary surfaces, we rely on physical and
numerical models to infer the subsurface processes linked to their
formation. Here, we use 3D seismic reflection data to quantify the
palaeosurface and subsurface geometry of pit craters. These data enable
us to identify whether pit craters connect to and their formation thus
related to underlying structures. We map 59, Late Jurassic pit craters
deeply buried within a sedimentary basin, offshore NW Australia. We
demonstrate that some pit craters extend down and appear physically
connected to igneous dykes, whereas others connect to dyke-induced and
tectonic faults, seemingly where faults are steeply dipping and
dilatational. There are no apparent relationships between pit crater
geometries (e.g., palaeosurface expression or vertical extent) and the
different magmatic and fault-related mechanisms we infer drove their
formation. Reflection seismology is a powerful tool for understanding
how pit craters form and whether their surface expression can be used to
reconstruct subsurface structures and processes on other planetary
bodies.