This element is not common on earth but shows far higher concentrations in meteorites. There is one supposed impact crater at Manicouagan in Quebec Province, Canada. Crater about 60km across of about the right age Towards the end of the Trias there was good evidence from Virginia and New Jersey of regular cyclical changes of sea level, giving cycles of sediment change. Each cycle is thought to have lasted about 21 000a. In each regular patterns of floral and faunal changes.
Cycles continue into the L.Jurassic, but in one cycle most of Triassic types vanish .
In pollen terms only ferns and lycopods remain, and today they are known to have the ability to survive for long periods before rejenerating. The Geology of Europe . The Geology of Western Europe . 1960 Palaeotectonic evolution of the central and western Alps.