¹David T. King Jr,^2,3Michael R. Rampino,¹Lucille W. Petruny
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14290]
¹Department of Geosciences, Auburn University, Auburn, Alabama, USA
²Department of Biology, New York University, New York, New York, USA
³Department of Environmental Studies, New York University, New York, New York, USA
Published by arrangement with John Wiley & Sons

The central uplift area of Araguainha impact structure (Brazil) includes a quartzite pebble- and cobble-bearing stratigraphic facies that have been profoundly affected by impact processes. These quartzite clasts have been studied previously for their planar deformation features (PDFs), but not with regard to their noteworthy transverse fractures. Petrographic study of transverse fractures within seven selected impact-affected cobbles from the conglomeratic fluvial facies of the target Devonian Furnas Formation (near the central uplift of Araguainha impact structure) has revealed that there is a micro-breccia within these transverse fractures, and this micro-breccia originated by comminution of the host cobble. Further, the transverse fractures in these cobbles have different styles (well-defined, poorly defined, complex, and diffuse) and are evidently post-shock, brittle deformation features. We suggest that a late compression-stage process, perhaps collapse of the central peak, may be responsible for the development of these transverse fractures.

¹Kevin Righter
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14289]
¹Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York, USA
Published by arrangement with John Wiley & Sons

ALH 84001 is an orthopyroxenite that is the oldest known Martian meteorite. Given this rock type and age, and the possible source locations, ALH 84001 represents an opportunity to learn more about basic geologic relations in the Martian highlands in the southern hemisphere. Its orthopyroxene-rich mineralogy is unique and also includes C-, S-, P-bearing minerals. ALH 84001 can provide constraints on chronology, geology and surface features, crust formation, paleomagnetism, weathering, climate, magmatism, and interior structure. When it was recognized to be of Martian origin (~1994), there were ~12 known Martian meteorite samples. That number is now >150, with only one other meteorite (NWA 7034) having clasts that are similar in age to ALH 84001. Thus, it remains a unique sample and continues to provide opportunities to understand this early period of Martian history.