Seismic Reflection Data Reveal the 3D Subsurface Structure of Pit Craters

Pit craters are quasi-circular depressions observed on rocky and icy planetary bodies, as well as numerous asteroids. Pit craters are thought to form by overburden collapse into a subsurface cavity or volumetrically depleted zone. Importantly, the surface size and distribution of pit craters may provide an important record of otherwise inaccessible subsurface processes. However, because we cannot access the subsurface of many planetary bodies, we rely on physical and numerical models to infer processes linked to pit crater formation. Here, we use 3D seismic reflection data to quantify the palaeosurface and subsurface geometry of 59 Late Jurassic pit craters buried to depths of similar to 3 km within a sedimentary basin, offshore NW Australia. The pit craters are typically funnel-like, with an inverted conical upper section underlain by a pipe. Pit crater depths, that is, the height of inverted cone sections, correlate with their plan-view length, consistent with observations of pit craters elsewhere; this trend is rendered less apparent by later sediment-infilling. For the first time, we show some pit crater pipes connect to underlying igneous dikes or steeply dipping, likely dilatational portions of normal faults. Although some pit craters seemed to have formed due to faulting and others to dyking, they cannot be differentiated based on their surface expression. Our data also suggest pit crater size may not relate to the mechanical properties of the host material. Overall, we conclude that the surface expression of pit craters on Earth and other planetary bodies may not be diagnostic of subsurface processes or properties.

Automated summary

Pit craters are depressions observed on planetary bodies, and their surface features may not accurately represent subsurface processes or properties. This study used seismic reflection data to analyze pit craters in a sedimentary basin offshore NW Australia, finding that they are typically funnel-like with an inverted conical upper section. Some pit craters were also found to connect to underlying igneous dikes or faults. Overall, the surface expression of pit craters may not be a reliable indicator of subsurface processes or properties.