Thirty-five gravity stations were added to a pre-existing gravity net over the Bærum cauldron and the Bouguer anomalies were computed. A positive anomaly lies over the south side of the cauldron. If the effect of the 1000-m-thick B3 basalt, which is down faulted into the cauldron, is removed, a 10-mgal. negative anomaly is found over the cauldron. This anomaly corresponds to a hypothetical vertical cylinder of nordmarkite 10 km in diameter and 6 km deep. Its top would be about 3 km below the surface. A small negative anomaly associated with contact-metamorphosed sandstones outside the cauldron is ascribed to a subjacent intrusive. A large negative anomaly is found over the nordmarkitic pluton comprising Tryvasshögda.
A regional gravity study over the Permian Bærum cauldron of the Oslo region
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