This succession from simple to complex in the layers of the earth is then used to date each layer according to the time scale developed and frequently amended during the past 150 years. An overthrust occurs when portions of the earth are pushed upward to form hills and mountains. Such layers may then come to rest on top of younger layers. No one would deny that overthrusts do in fact occur. Serious questions are raised, however, when enormous areas are found to have fossils in the 'wrong' order and there is no evidence whatsoever that overthrusts occurred.
Some examples follow where something other than an explanation of overthrusts is called for.
When Precambrian strata seem to be deposited by water on top of Cretaceous formations, billions of years of rock are resting in the wrong place. Field work carried out in 1968 resulted in the above conclusion. This geologic puzzle is the Lewis Overthrust, which extends from Glacier National Park 350 miles into Alberta, Canada, in a strip 15-30 miles wide. This phenomenon is cited in the texts as the classic example of a large overthrust, that is, older rock pushed up and out over younger rock. The fossils are in the wrong order.