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Figure 8.26 Track of Mariana reference point from 0 to 100 Ma.

other half is buried beneath the St Lawrence River. The Siljan structure in Sweden is currently exposed at a height of about 500 feet. It is possible that one or both of these localities were covered by sea-water at the time of impact. In any event, it is interesting to note that the Siljan event, dated at 368 Ma, occurs within 1 Ma of the assigned Famennian/Frasnian stratigraphic boundary at 367 Ma. The Charlevoir event is dated at 357 Ma, which is within 1 Ma of the Ivorian/ Hastarian stratigraphic boundary at 356 Ma, or possibly the Devonian/Carboniferous subera boundary at 360 Ma.

Figure 8.27 Track of Fennoschandia from 250 to 600Ma. (a) Track from 250 to 350 Ma. (b) Track from 350 to 450 Ma. (c) Track from 435 to 600 Ma (Note change in viewing direction as inferred from latitude and longitude.) (9 anomalies).

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