Jacob Clarke, in his weekly Substack newsletter “Let’s Talk Outcrop”, posted a story about the geology of the Grand Canyon entitled “The Great Unconformity”. Clarke introduces us to the rock layers there: “… which are incredibly well-preserved, well-exposed, and relatively accessible. The oldest rocks at the base of the canyon are roughly 1.8 billion years old and the youngest are approximately 200 million years old. The geologic sequences in the Grand Canyon then, represent nearly 2 billion years of geologic time.
(above) Stratigraphic column of rocks of the Grand Canyon region showing the three sets of rocks and major unconformities: Great Nonconformity (white line), Great Angular Unconformity (red line) and Great Unconformity (black line). Fm = Formation; Ss = Sandstone; Ls = Limestone. (National Park Service)
These sedimentary layers preserve fossils of the organisms that lived during each time period along with chemical compositions representative of the atmosphere and climate at the time of deposition.
In the above image, a large gap in time between the tilted Vinshu basement rocks and flat, overlying Paleozoic geologic layers is evident. This means that over one billion years of geologic time are missing in some regions of the Grand Canyon at the boundary called the Great Unconformity. This missing time in the Grand Canyon has been attributed to a long period of erosion and uplift to the tilted stratigraphy of the rocks underlying the Great Unconformity. “
In 2012, University of New Mexico professor, Dr. Karl Karlstrom wrote: “The main erosional unroofing (the great- est unconformity), and the most rock removed by erosion, are now marked by this contact between the basement rocks and the basal Unkar Group, an erosional episode that took place between 1660 and 1255 Ma and that removed a thickness of >20 km (12.4 mi) of rock from the region. This would be analogous to taking high mountains, like the Alps, and eroding them down bit by bit to form a flat erosional surface that exposed rocks that were once 20 km (12.4 mi) deep in the core of the mountain belt”
(above) Geologist with his hand on the Great Unconformity at the Grand Canyon. Photo by Laura Crossey.
In 2012, Peters and Gaines published a possible explanation as to why there is widespread erosion on continents that led to such a vast period of missing geologic time. They propose that marine sediments above the Great Unconformity record the expansion of global and continental seas and increased oceanic alkalinity. The geochemical markers they analyzed suggest that chemical weathering of continental crust was increased during the time periods represented by the Great Unconformity, and was promoted by increased ocean levels and continental weathering.
Question: What was the root cause of significant sea level rise and the increased continental weathering over the 400 million years that these events occurred?
From our hypothesis - The Story of Climate Change:
“If the Milky Way is a 4-arm spiral galaxy and if the galactic structure and our orbital location derived radiation exposure drives the global climate, then, the 675-million-year climate response model (Fig 6) represents one full orbital transit of the Milky Way spiral structure. Would these unique alternating sequences of warming and cooling periods, driven by modulated cosmic radiation, persist during subsequent or previous orbital transits? Would this radiation pattern then be imprinted on the Earth's climate to be preserved in sedimentary carbonates for billions of years?
Archean-Mesoproterozoic Isotope Data (1000 to 3500 mya)
If the climate/cosmic radiation hypothesis is true and that the ancient Earth retained liquid water and life almost from the beginning, a deep time geological record laid down in the sediments should reflect a unique proxy climate signature imprinted on early Earth oceans. Our linear 930-million-year climate reconstruction (“The Splice”, Fig. 4) reflects temperature, time and galactic orbit location and can be used to construct a template for predicting and locating deep time climate changes as indicated by the isotope record in the literature.
Three complete climate cycles (2 billion years), have been graphically flipped, spliced and scaled to provide a concurrent roadmap to the Archean-Mesoproterozoic data. The variability of hot and cold climate periods of the template should coincide with similar climate variability implied by the isotope excursions in the *The Geologic Time Scale* data.
As our climate template contains three full climate cycles, with significant Archean and Mesoproterozoic data coincidence, it seems convincing that a unique repeating pattern of climate change driven by galactic orbit with accompanying galactic radiation variability has been imprinted on the Earth’s climate from the beginning.”
From “The Geologic Time Scale”, Gradstein et al, 2012 (Fig 10), for the Archean and Mesoproterozoic data (1000 to 3500 million years ago), positive carbon isotope values above the green “0” line indicate warmer climates while negative values below the green line indicate cooler.
Galactic structure driven climate cycle explanation
In the above image, we can see that the Great Unconformity erosion period between 1660 to 1255 million years ago (mya) contains a major Icehouse period (Sagittarius spiral arm crossing) centered at 1315 and spanning 1455 to 1255 million years ago. This time period includes the climatological equivalent to the famous replayed Cryogenian Period of 720 to 635 million years ago – also a Sagittarius spiral arm crossing and home of the Snowball Earth hypothesis. Here we have it – an expansive Icehouse containing at least four Ice Ages. As with all Ice Ages, they are modulated by the Earth’s Milankovitch orbital cycles driving the ice to rhythmically advance and retreat until they are terminated by the warming temperatures promoted by our planetary system’s galactic out-of-plane orbital oscillation - with an accompanying sea level rise. The Ice Ages force massive terrestrial glacial expansion including snowball scenarios with subsequent melt-water flooding periods. The Sagittarius Icehouse is preceded in time by a Hothouse centered at about 1625 mya (replayed as the Permian), then our orbit takes us into the diminutive Scutum-Crux spiral arm Icehouse from 1600 to 1475 mya. Scutum-Crux is the home of the Triassic and Jurassic periods. Next, we enter the Hothouse centered at 1425 mya (replayed as the Cretaceous). The cold and icy Sagittarius Icehouse is then followed by the Hothouse centered around 1175 mya which is the climatological equivalent of the replayed Cambrian Period. The inter-arm space Hothouse transits are accompanied by lower cosmic radiation flux, less ionization, fewer aerosols, fewer clouds, and warmer climates while the Icehouse crossings are high cosmic radiation zones with increased ionization, more clouds and colder climates. Under the right climatological conditions and geographical locations, massive terrestrial glacial ice-melts can drive punctuated sedimentary rock erosion with preceding and follow-on Hothouses promoting hotter, wetter, and rainier conditions driving higher sea levels and increased continental weathering.
Regards,
Kirby Schlaht
The Story of Climate Change home page