Plate tectonics appears to have no accepted explanation for the widely recognised cycles of kilometre scale uplift and subsidence - why they appear to have such regular periodicity measured in many 10’s million years, why they seem to occur synchronically over widely dispersed geographic domains, and why they so often occur at locations where plate tectonics suggests passive tectonic activity. This short paper reconsiders these cycles of uplift and subsidence so strongly in evidence within the Grand Canyon area, and especially the timing of the onset of new pulses of sedimentation as revealed by the dates of strata immediately above the major unconformities. This suggests that commencement of new pulses of marine sedimentation initiating continuous kilometre scales of burial have a strong periodic signature of circa 130Ma. It is demonstrated that these recommencements of burial of often mega sequences of sediment occur when earth climate is emerging from ice-house to hot-house conditions. Furthermore, it is pointed out that recognised periods of mountain building have similar 130Ma periodicity with phasing closely aligned with periods when earth is experiencing ice-house conditions. Tentative explanations as to why changes in climatic conditions could account for these kilometre scales of uplift and subsidence focus on the associated changes in the surficial disposition of ice and water associated with ice- and hot-house conditions and how this effects the geothermal flux. Changes in geothermal flux will as a result of phase changes at the lower crustal boundary produce changes in crustal thickness and hence crustal buoyancy, accounting for both the massive cycles of burial and those of exhumation.
Evidence of kilometre scale uplift and subsidence at locations remote from any recognised plate boundaries, the existence of mega-sequences of post-rift marine sediments over widespread intra-cratonic areas, and the consideration that pulses of deposition display a clear periodicity and synchronicity over widely dispersed spatial domains, remain largely unresolved issues within current geological theory. While the exact timing of uplift and erosion associated with major unconformities are difficult to assess, the age of sediments immediately above provide vital temporal markers for the onset of subsidence and associated sea level rise. By reconsidering the much studied sedimentary sequences of the Grand and Bryce Canyon areas the following will show that the at least over the Phanerozoic eon the initiation of new pulses of deposition occur at times when earth climate is emerging from ice-house to hot-house conditions. Furthermore, the recorded periods in which global occurrences of epeirogeny have occurred will be shown to correlate closely with the end of hot-house periods and the onset of ice-house global climate conditions. Finally, some tentative thermo-geodynamic explanations for this apparent causal link between global climate and vertical tectonics will be suggested.