Some Further Comments on what the Colorado Plateau Tells Us

The most recent posts have been based upon the rejected paper submitted to what was a new publication venture by UCL in 2019. This paper attempted to use the fascinating geology exposed within the canyons and the geomorphology of the Colorado Plateau and contiguous areas to assess whether a hypothesised mechanism for explaining the well recognised and often massive rises and falls of continental and oceanic lithosphere might have any relevance. This afterall is an area of geology that seems to be very poorly covered within the current prevailing paradigm of plate tectonics. And as noted at the start of this new burst of blogging activity, these posts, like the paper on which they have been derived, have concentrated on the sedimentary sequences of the Grand and Bryce Canyon areas simply because they are so clearly exposed and thoroughly researched. Furthermore, as the stratigraphic geometry shown in Fig 4 of the 8^th August post seems to demonstrate, the Grand Canyon area in particular has recently, and certainly post hypothesised "breakup", been subject to major uplift and what on the face of it seem to be ice sheet erosions. Earlier sequence stratigraphy also suggests that this area has been subject to repeated cycles of ice- and hot-house climate cycles and consequently what appears to be a direct correlation of tectonic activity and climate. But clearly the massive erosion occurring during the ice-house phases must produce in contiguous areas equally massive accumulations of ice erosion deposits, suggesting a counter-phasing of deposition in areas contiguous with those directly affected by the growth of ice-sheets – and of course vice versa during the erosion of possibly uplifted areas during hot-house climatic conditions.   

From the direct evidence of the Grand Canyon, along with the reported synchronicity over craton-wide and even continent-wide areas noted by Sloss and others, there appears to be strong evidence of a causal link between cycles of uplift and erosion during ice-house global climate, and subsidence and deposition during hot-house climatic conditions. It is therefore surprising that the thermo-geodynamics underpinning these links have not been more thoroughly investigated. If as suggested there is a causal link between at least vertical tectonics and global climate cycles this could significantly add to our ability to explain other important aspects of global tectonics. As opined at the 2017 meeting at the Geological Society of London the current version of the mobilist concepts do not adequately explain the all too clear evidence within the Colorado Plateau of cyclic ups and downs of the lithosphere. Nor do these concepts account for the seemingly strong evidence that these ups and downs seem to occur in a regular cyclic pattern. Changing climatic domains exposed within the sedimentary record are currently accounted for by invoking major latitudinal movements of continents. By looking at Earth climate records it seems clear that these records can be equally accounted for without the need to move continents around quite so much!

Fig 12. Crossection covering the area between Brian Head and the Grand Canyon. 

Horizontal scale 20 times verttical scale to emphasise vertical tectonic motions.  

Fig 12 is a redrawn cross-section linking the relatively high point at Brian Head down through the Grand Staircase to the incision of the Grand Canyon created by the recent (geologically speaking) erosion by the Colorado River. The vertical scale is exaggerated by around 20 fold relative to the horizontal scale to emphasise some of the important tectonic features. First, is the massive regional uplift of the sedimentary sequences covering the 500 Ma from the Cambrian sequences of the Tonto Group (-525 Ma) through to the residual late Mesozoic sequences of the Grand Staircase (-40 Ma). Not shown clearly at the left of the Brian Head is a steeply sloping fault within which the sedimentary sequences beneath Brian Head have been uplifted by around 2 km relative to the matching sequences to the left (name?). Furthermore, at some time after -40 Ma the post Cambrian sequences in the Grand Canyon area have been domed-up by as much as 2.2 km relative to the area beneath Brian Head. Whatever induced these post -40 Ma massive relative motions clearly involved tremendous tectonic forces. It is worth noting that this 4 km depth of sediments would have been laid down horizontally and remained so up to some time after -40 Ma when a process of erosion kicked-in.