Flood traps through space and time and their bearing on some problems of geotectonics

A study of world stratigraphy reveals, somewhat unexpectedly, that there were extensive basalt flows in the early Precambrian, but the Upper Precambrian and the whole of the Palaeozoic Era, with some insignificant exceptions, are practically devoid of flood basalts. In fact there were very few cruptions between about 1000 M.yr. and about 200 M.yr, ago. Since Upper Triassic time, however, basalt floods have come to cover very extensive areas in both the hemispheres, and the activity is continuing almost unabated. Recent researches on the origin and nature of the mid-ocean ridges have indicated that the flood basalts are apparently genetically connected with these ridges which appear to have begun to open the present oceans within the past 150 M.yr. Basalts occur on the opposite coasts where the continents were formerly together, for example, Peninsular India and Eastern Africa. However, along certain coastal areas there are no basalts of appropriate age even though a mid-ocean ridge exists beyond these. This is true, for example, of eastern North America and western Europe. Elsewhere neither basalt flows nor a mid-oceanic ridge exist where the continents are reasonably believed to have been together. These anomalies call for an explanation, and it is suggested that the observed features can be explained by the fact that two distinct phenomena, crustal sliding and global expansion, have been responsible for the present disposition of the continents. The net result of these two activities has been recognised as ‘Continental Drift’.