A matter of minutes: Breccia dike paleomagnetism provides evidence for rapid crater modification

摘要: During an impact event, a crater’s transient structure adjusts gravitationally. Within medium-sized complex craters, central uplift rises and collapses resulting in large-scale rotations of the target rock. Estimated crater modification rates from numerical models indicate that craters modify to structurally stable state within tens seconds several minutes after excavation. However, there is little direct geologic evidence constraining these rates. We show how paleomagnetic measurements lithic breccia dikes emplaced during excavation can be used constrain rate ∼34-km-diameter Slate Islands structure, Ontario, Canada. The uniformity linearity directions among clasts matrix throughout were frictionally heated above magnetite Curie temperature (580 °C) their emplacement subsequently cooled situ through magnetic blocking temperatures. tight grouping implies locked remanence over time interval which was not experiencing structural had already reached state. Conductive cooling thinnest sampled dike would have led recording approximately six emplacement. This constraint necessitates only presents rare case geological process resolved on such short scale.