Hays et al (1976) showed that variant orbital geometry was the "pacemaker" of the Ice Ages. They referenced James Croll (1875) among others. Croll also had presented calculations to demonstrate an equivalent relationship. Lyell tried unsuccessfully to apply Croll's astronomical data to climatic variation and envisioned large scale subsidence and elevation as the primary control of the Ice Ages. Croll argued against Lyell's use of orbital geometry and his geochronological model, taking 250,000 BP as the start of the glacial epoch, which by his calculation corresponded to the most recent and greatest orbital eccentricity. Both Croll and Lyell, in different ways, were on the right track, but technically updated astronomical data as well as microfossil indicators of oceanic temperature used in the modern synthesis, were needed.

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