Further constraints on the formation of the Siljan impact crater from seismic reflection studies

Abstract

Recently acquired seismic reflection data over the Siljan Ring structure support previous estimates of the dimensions of the excavated crater made from earlier seismic data. The data are consistent with a present-day excavated crater diameter of 22 km and a minimum depth of 3 km. Allowing for erosion, these depths correspond to a maximum excavated crater diameter of 26 km and a minimum depth of about 4.5 km upon impact. The excavated crater diameter is at the lower limit or slightly less than what would be expected based on empirical relations from crater mechanics using a final rim diameter of 52 km. The structural uplift is less well defined on the new data, with the profile running closer to the center of the crater, but the data indicate an uplift of about 2 km at 9 km depth. The current data set together with previous reflection data strongly support an impact origin for the Siljan Ring structure and indicate that the crust below 15 km was not involved in post-impact vertical movements.

Key Words:

• Siljan Ring
• meteorite impact
• seismic reflections
• central uplift
• excavated crater
• dolerite sills