LATE ORDOVICIAN EXTINCTIONS AND SEA-LEVEL CHANGE

If Ordovician continental blocks had similar hypsometries to modern co ntinental blocks, glacially-induced regressions would have increased s hallow water areas. Thus species/area effects cannot be invoked to exp lain extinctions during these regressions. Because late Ordovician sea level was so high, glacially-induced regressions of similar magnitude s to Quaternary regressions would have dramatically increased the inpu t of dissolved load into the shallow sea. This 'pollution' effect may have been one cause of the extinctions.