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The Meaning of the Great Unconformity and Sauk JOURNAL OF CREATION 28(1) 2014 || PERSPECTIVES distinctive stratigraphic surface in The meaning the rock record.”1 The Great Unconformity is also of the Great considered a unique feature within Unconformity the last 900 Ma of uniformitarian time.2 The Tonto Group in the Grand and Sauk Canyon is also recognized as covering about half of North America and is Megasequence called the Sauk Megasequence,1 the bottom of six megasequences that Michael J. Oard supposedly account for sedimen- tation over North America. The Sauk sequence is well defined lithologically he Great Unconformity, first on top of the upper crust and locally defined in the Grand Canyon T on Precambrian sedimentary and in 1869, separates the Cambrian metasedimentary rocks. However, Tapeats Sandstone from the underlying the other five sequences are based Precambrian rocks (the geological on many assumptions, such as fossil column and timescale are used for dating and not lithology, and are discussion purposes only). There commonly missing large sections in is some confusion in the Grand North America (see below). Canyon in that there is a second major unconformity between the Precambrian sedimentary rocks and The Great Unconformity in the igneous and metamorphic rocks Montana and Wyoming (figure 1). The uniformitarian origin of the Great Unconformity is supposed I have observed the Great Un- to be slow denudation over about a conformity at several locations in billion years that resulted in a nearly Wyoming and Montana. Whereas flat planation surface. Then after the Great Unconformity is near the this denudation, a shallow marine bottom of 1,200 m of flat strata in the transgression deposited the Tapeats Grand Canyon, it occurs at the tops of Sandstone, Bright Angel Shale, and some mountain ranges in Wyoming Muav Limestone in a fining upward and Montana. For instance, there are sequence called the Tonto Group. planation surfaces on the granite and It is now known that the Great gneiss of the Beartooth Mountains, Unconformity has a wide extent over Wind River Mountains, Bighorn North America, as seen on top of the Mountains, and locally in the northern upper crust. The Great Unconformity Teton Mountains (figure 2). is a distinctive physical boundary However, there has been confusion between mostly igneous rocks of the on the timing of the formation of upper crust and a layer of sandstone. the mountaintop planation surfaces, It apparently also occurs on other i.e. whether these planation surfaces continents: represent the Great Unconformity. “The Great Unconformity is well This is because there are planation exposed in the Grand Canyon, but surfaces that formed in the area after this geomorphic surface, which the time of the Great Unconformity. records the erosion and weathering For instance, a planation surface exists of continental crust followed by on the westward-dipping sedimentary sediment accumulation, can be rocks on the west side of the Wind traced across Laurentia and globally, River Mountains (figure 3) at about including Gondwana, Baltica, the same elevation as those on the Avalonia and Siberia, making it granite and gneiss. A planation surface the most widely recognized and also exists on the top of the southern 12 PERSPECTIVES || JOURNAL OF CREATION 28(1) 2014 Absaroka Mountains. These planing and filled in the depression left after the locally when a river floods and erodes events are much later in ‘geological gravity slides.5 After deposition and its banks.7 Planation surfaces are being time’ and so have caused some planing of the Absaroka Mountains, destroyed by present-day erosion, geologists to believe that the planing extensive erosion set in to erase the especially by running water that forms event also included the flat-topped planation surface in the northern channels and valleys. Geomorphologist granite and gneiss mountains of the portion and produce canyons up to C.H. Crickmay states: upper continental crust: “The age and about 1,200 m deep. “There is no reason to suppose that origin of the high-level erosion surface any kind of wasting ever planes [in the Wind River Mountains], the an area to flatness: decrepitation Problems with the uniformitarian Rocky Mountains and others have been always roughens; rain-wash, even explanation the subject of much debate.” 3 on ground already flat and smooth, The Absaroka Mountains represent The uniformitarian scientists tends to furrow it.” 8 volcanic breccia flows, called the claim that the Great Unconformity After the supposed long forma- Absaroka Volcanics, that have piled represents a long period of continental tion of the Great Unconformity, the up about 1,800 m deep over an area of denudation, well over a billion years Sauk Megasequence then was spread 23,000 km 2 and contain multiple levels at many locations. This is in the over much of North America. It is of vertical petrified trees at numerous context of attempting to explain the believed to represent a continental locations.4 They are dated Eocene, evolution of biomineralization by transgression of the sea but seems which is early Cenozoic, within the means of the geochemical effects of contradictory in that the fining uniformitarian geological column. prolonged continental weathering and upward sequence is so widespread The flows occurred after the Heart denudation.6 However, erosion does not over large areas. A rising sea level Mountain and South Fork detachments, form planation surfaces today, except in such a transgression would be Figure 1. The Great Unconformity of the Grand Canyon (upper arrow) above another nearly-flat unconformity between Precambrian sedimentary rocks, dipping downward toward the right, and the igneous and metamorphic rocks below (lower arrow). 13 JOURNAL OF CREATION 28(1) 2014 || PERSPECTIVES would scour the continents down to a planation surface, even causing the second major unconformity below Precambrian sedimentary rocks in the Grand Canyon. It would also greatly erode the surface and pulverize the sediments into fine particles. Little deposition would occur at this point, except in protected deep basins that are likely impact basins.10 With the waning of the early Flood mechanism, currents and turbulence would decrease and the ‘Great Deposition’ would occur. This deposition resulted in the thick Paleozoic and Mesozoic sediments that we observe over much of the continents today. These sedimentary rocks are little deformed, widespread, fine- grained, and show little, if any, erosion within and between the layers, as if all these widespread sediment layers were deposited in one single uninterrupted sequence. In fact, such deposition was Figure 2. The top of Mount Moran, Grand Teton National Park, Wyoming, US, showing the Great Unconformity with a 15 m erosional remnant of Flathead Sandstone (arrow).4 The vertical black rock admitted by three geologists for the is a dike of diabase, a basalt-like rock. early to middle Paleozoic sedimentary rocks uplifted in the Teton Mountains expected to produce a more chaotic erosional remnants have been left on of northwest Wyoming: distribution of sediments with much top of the planation surfaces, such “The regularity and parallelism of conglomerate over short lateral and as Beartooth Butte on top of the the layers in well-exposed sections vertical spatial scales—unlike the Beartooth Mountains and a 15-m suggest that all these rocks were thick remnant of Flathead Sandstone, deposited in a single uninterrupted Sauk Megasequence. 11 equivalent to the Tapeats Sandstone sequence.” in Grand Canyon, on top of Mount However, the geologists do A possible diluvial explanation of Moran (arrow in figure 2). The other not believe their eyes and stretch the Great Unconformity and Sauk mountaintop planation surfaces on the the deposition of this 600-m thick Megasequence? west side of the Wind River Mountains sequence into 200 Ma because of and the Absaroka Mountains would their stretched-out timescale. Such I have come to the conclusion that then represent planation during Flood great time injected between the layers the mountaintop planation surfaces runoff. makes no sense based on present day on the granite and gneiss of some The Great Unconformity and Sauk erosional patterns that can erode all Wyoming and Montana mountains Megasequence, plus the later planation the continents to sea level in a few tens is really the Great Unconformity that surfaces, can be explained by Flood of millions of years. Based on erosion has been exhumed from under thick catastrophic processes. A possible today, which is an application of the sedimentary rocks. The evidence for model for the formation of these uniformitarian principle, the data do this is that thick sedimentary rocks features follows. The early Flood not support such long time periods still cover many mountain ranges of unleashed the mechanism of the subjectively interjected within the the Rocky Mountains, such as the Owl Flood, which I think was caused by sedimentary rocks. Creek Range that makes up the southern impacts.9 The very early Flood should Such widespread deposition of boundary of the Bighorn basin. The be the most catastrophic part of the many layers, one on top of the other, mountains apparently did not uplift Flood, and with multiple impacts with little or no erosion is what we enough for all the sedimentary rocks very strong currents and turbulence would expect during the early Flood.12 to be eroded off. Moreover, Paleozoic would occur. Such a mechanism The first megasequence, the Sauk, is 14 PERSPECTIVES || JOURNAL OF CREATION 28(1) 2014 well defined as it covers about half sedimentary rocks.13 For instance, the The Flood can indeed explain the of North America, but it looks like Uinta Mountains of northeast Utah rose big picture geology of the continents, the other five megasequences are up 12 km relative to the adjacent basins including the Great Unconformity, sketchy with missing megasequences during the Cenozoic.14 That is why the the Great Deposition starting with over large areas of North America.
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