Periods of evaporite maxima (warm worldwide climate, high S³⁴/S³² isotope ratios in salts, restriction of coal and petroleum formation to high altitudes, and crossings of the galactic plane by the solar system appear to coincide well with periods of mass biotal extinctions. The most notable extinctions took place at times when the solar system was crossing the galactic plane while in a perigalactic position in its orbit. The large amounts of cosmic radiation and high worldwide temperature during the solar system crossings of the galactic plane could, and should, have created high cosmic radiation--a condition potentially inimical to the survival of many biota. Thus the complex interactions among ocean-water salinity, changes increasing S³⁴/³² ratio, salt precipitation, increasing aridity at low and middle latitudes, increase in land area and decrease in epicontinental seas (following Late Paleozoic orogenies), and crossing of the galactic plane by the solar system could have led to the worldwide biotal extinctions of Permian-Triassic times.

Assuming that a relationship between these various factors existed, the author plotted curves for several of these phenomena, from Middle Proterozoic to Quaternary time: a curve for evaporite-maximum and evaporite-minimum periods of earth history, a curve for changes in S³⁴/S³² ratio, curves for times of maximum biotal extinctions and a curve for galactic orbital and oscillatory motions. The shapes of all curves so nearly coincide that a close interrelationship seems to be established between each of the phenomena that were plotted. Therefore, a good case can be made for postulating that times of mass biotal extinctions are closely related to the position of the solar system with respect to the galactic plane during galactic orbit.

End_of_Record - Last_Page 340-------