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During continental breakup, the locus of strain shifts from a broad region of border faulting and ductile plate stretching to a narrow zone of magma intrusion in a young ocean basin. Recent studies of volcanic rifts and margins worldwide suggest this shift occurs subaerially, before the onset of seafloor spreading. We test this hypothesis using recently acquired seismic reflection and borehole data from the Danakil Depression, Ethiopia, a unique region of transition between continental rifting and seafloor spreading. Our data, located near Dallol, ~30 km northwest of the Erta'Ale Volcanic Segment, reveal a remarkably thick (>1‐km) sequence of young (~100‐ka) evaporites in a basin bound by a major (≤400‐m‐throw), east‐dipping normal fault. To generate such a large amount of subsidence in such a relatively short time, we propose that upper‐crustal extension in Danakil is currently dominated by faulting, not magmatic intrusion. Given the region's markedly thinned crust (~15‐km‐thick), relative to elsewhere in Afar where magma‐assisted rifting dominates and maintains crustal thickness at ~25 km, mechanical extension in Danakil is likely coupled with ductile extension of the lower‐crust and mantle lithosphere. Despite proximity to the voluminous lavas of the active Erta'Ale Volcanic Segment, evidence for igneous material in the upper ~2 km of the 6‐ to 10‐km‐wide basin is limited. Late‐stage stretching was likely aided by thermal/strain‐induced lithospheric weakening following protracted magma‐assisted rifting. Basin formation immediately prior to the onset of seafloor spreading may also explain the accumulation of thick marine‐seepage‐fed evaporite sequences akin to those observed, for example, along the South Atlantic rifted margins. New seismic reflection, and borehole data from the Danakil Depression, Ethiopia, constrains late‐stage continental breakupA thick sequence of evaporites has been deposited over tens to hundreds of thousands of years in a basin bounded by a major, E‐dipping normal faultThe onset of magmatic extension during continental rift development does not necessarily herald the onset of seafloor spreading

The geometry and growth of normal faults are fundamental to the evolution and petroleum prospectivity of sedimentary basins, controlling trap development; source, reservoir, and seal rock distribution; and fluid flow. The poorly studied, petroliferous Ceduna Subbasin located offshore southern Australia contains an east-southeast-striking, gravity-driven fault array, which soles out onto a southwest-dipping detachment horizon. These gravitydriven faults displace the White Pointer delta and overlying Hammerhead delta. Within the subbasin, structural closures bound by these gravity-driven faults represent the main exploration targets. Determining when these faults and associated traps formed relative to petroleum generation and migration and, more specifically, if the faults reactivated is thus critical to understanding the prospectivity of the Ceduna Subbasin. In this study, we use a time-migrated two-dimensional (2-D) seismic reflection survey covering the central Ceduna Subbasin to constrain the geometry and kinematics of the fault array. Throw patterns reveal that most faults nucleated in the Cenomanian. Although some faults display evidence for continuous growth by upper tip propagation throughout the Cenomanian to Maastrichtian, it is apparent that other faults were inactive during the Turonian-Santonian, before reactivating and propagating upward or dip-linking with overlying, newly formed faults during the Campanian and/or Maastrichtian. Faults that grew continuously during the Cenomanian to Maastrichtian primarily formed in the center of the study area, whereas reactivated faults developed in landward positions. Faults that formed because of dip linkage developed in seaward positions. We suggest that this spatial variation in fault growth style was controlled by compositional and mechanical heterogeneities in the Tiger and lower Hammerhead supersequences, which mark the boundary between the two delta systems. In addition to providing insights into the petroleum prospectivity of the Ceduna Subbasin, this study shows how 2-D seismic reflection data can be used to probe the kinematics of normal faults. [ABSTRACT FROM AUTHOR]

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 ∼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. Linear chains of small craters are commonly observed on planetary bodies like Mars, Enceladus, or various asteroids. These depressions, called pit craters, are not related to meteorite impacts. Because pit craters are of a similar shape and size to features observed on Earth and created in laboratory models, we think they form when rock collapses into holes present beneath the surface. Previous studies have not been able to work out how these holes form, because we cannot easily look beneath the surface of other planetary bodies. In this study we use a technique called seismic reflection, which uses sound waves to create an ultrasound‐like 3D image of Earth's subsurface. By doing this, we see the shape and can explore the origin of pit craters found offshore Australia that are ∼148 million years‐old and now buried several kilometres beneath the seabed. We show that some of the studied pit craters are connected to igneous dikes (solidified vertical sheets of molten rock) and others to faults (cracks in the rock). Our overall finding is that pit crater shape and size do not necessarily tell us much about the process(es) that formed them, or the properties of the material in which they formed. We image and quantify the palaeosurface and subsurface 3D geometry of pit craters in Australia that formed in the Late JurassicPit craters are physically connected to upper tips of igneous dikes or steeply dipping, dilatational portions of normal faultsWe find no apparent relationship between pit crater geometry and formation mechanism We image and quantify the palaeosurface and subsurface 3D geometry of pit craters in Australia that formed in the Late Jurassic Pit craters are physically connected to upper tips of igneous dikes or steeply dipping, dilatational portions of normal faults We find no apparent relationship between pit crater geometry and formation mechanism