The Sauk transgression was one of the most dramatic global marine transgressions in Earth history. It is recorded by deposition of predominantly Cambrian non-marine to shallow marine sheet sandstones unconformably above basement rocks far into the interiors of many continents.
How did the Sauk sequence get its name?
These sequences were given names. The oldest was the Sauk, followed by the Tippecanoe, Kaskaskia, Absaroka, Zuni, and Tejas. The names of these have their various origins, but geological names are always linked to a physical location. The Sauk Sequence get its names from rocks in the vicinity of Sauk County, Wisconsin.
What is the sloss sequence in North America?
Sedimentary “Sloss” Sequences of North America. In the Mid-Atlantic region, the Sauk, Tippecanoe, and Kaskaskia are well exposed. White and yellow areas represent major marine transgressions onto the craton while black areas represent major unconformities (sequence boundaries).
Is the Sauk a 2nd order supercycle?
The Sauk is bounded on the bottom by the “Great Unconformity”, the boundary between the Sauk and Tippecanoe is referred to as the “Knox Unconformity”, and the boundary between the Tippecanoe and Kaskaskia is the “Wallbridge Unconformity”. All six of Sloss’ Sequences are 2nd order supercycles. (Sloss, 1964)
What caused the Sauk transgression?
The transgression is attributed to thermal subsidence following the breakup of the supercontinent of Rodinia, combined with a rise in global sea level due to climate change or shifts in global tectonics.
When did the Sauk sequence end?
about 490 million years agoThe sauk sequence was terminated abruptly about 490 million years ago when sea level suddenly dropped (on geological timescales, taking a few million years), leading to widespread erosion and the formation of a worldwide unconformity surface on top of the sauk sequence.
When did the Sauk sequence occur?
The Sauk sequence in Illinois consists of Cambrian and Lower Ordovician rocks deposited approximately 543 to 490 million years ago (mya). The sequence is named for Sauk County in southwestern Wisconsin, where it rests on the Precambrian Baraboo Quartzite and lies unconform- ably beneath the Middle Ordovician St.
What rock formation is the base of the Sauk transgression?
Based on various lines of evidence preserved in the rock record, Cambrian sandstone appears to have first been distributed by wind and rivers. The Sauk transgression that followed caused marine reworking of much of that sand.
What happens during transgression?
Transgression occurs when the ocean basins have more quantity of water than their capacity. It can also occur when the land starts sinking into the sea. It results in a flood that is known as transgression.
Which was the first major transgressive sequence onto the North American Craton?
The first major transgression onto the craton during the Paleozoic was the Tippecanoe. The four Paleozoic transgressive sequences are in order from oldest to youngest are Sauk, Tippecanoe, Kaskaskia, and Zuni. During a transgressive sequence, sedimentary facies migrate oceanward.
How was the great unconformity formed?
They were originally formed 1.85-1.65 billion years ago as several complex sets of sedimentary and volcanic rocks, were metamorphosed to schist and gneiss by burial and heating by granites at ~1.4 billion years, and then cooled and exhumed to form a flat, rocky plain at about 550 million years.
What caused the Tippecanoe sequence?
It is an erosional surface resulting from a rapid drop in sea level. Throughout the Tippecanoe, sea level is transgressing onto the craton. As average sea level rose, there were fits and starts of smaller sequences, higher order sequences, within the Tippecanoe.
What marks the boundary between the Sauk and Tippecanoe sequence?
The Sauk-Tippecanoe boundary in this region is at the base of the St. Peter Sandstone.
What is meant by transgression and regression?
Transgression: the landward migration of the shoreline (i.e., flooding of once-dry land) Regression: the oceanward migration of the shoreline (i.e., draining of flooded land)
What is a craton in geology?
craton, the stable interior portion of a continent characteristically composed of ancient crystalline basement rock. The term craton is used to distinguish such regions from mobile geosynclinal troughs, which are linear belts of sediment accumulations subject to subsidence (i.e., downwarping).
What is the oldest sedimentary rock deposited on the North American Craton?
What is the oldest sedimentary rock deposited on the North American craton? Bright Angel shale. n what kind of depositional environment were the sediments of the Sauk sequence deposited? Clean sandstones indicate shallow nearshore environment, carbonates indicate shallow, clear, warm sea.
When did the Tippecanoe sequence end?
The Tippecanoe sequence ended with a regression in the early Devonian, to be followed later by the Kaskaskia sequence.
What caused the Tippecanoe sequence?
It is an erosional surface resulting from a rapid drop in sea level. Throughout the Tippecanoe, sea level is transgressing onto the craton. As average sea level rose, there were fits and starts of smaller sequences, higher order sequences, within the Tippecanoe.
What is a Sloss sequence?
Sloss in 1963. Each one represents a time when inland seas deposited sediments across the craton, while the upper and lower edges of the sequence are bounded by craton-wide unconformities (time gaps in the rock record) that indicate when the seas receded and erosion occurred rather than deposition.
What rocks are typical of the Kaskaskia sequence?
The Kaskaskia sequence is dominated by carbonate rock but also contains siliciclastics—shale, siltstone, and sandstone. These rocks were deposited in the Illinois Basin over a pe- riod of about 60 million years.
How many measurements of zircon reference material were used to calibrate the session?
Higher-precision dates were obtained using an 18.5 s background and longer 25 s ablation period. Eighteen measurements of zircon reference material 91500 were used to calibrate the session and eight measurements of each of the zircon reference materials Temora2, FC1 and 1242 were used to validate the method. To fit the second ablation on the grains, a smaller beam diameter of 22 µm was employed. A laser energy of 2 J cm −2 and repetition rate of 7 Hz resulted in a pit ~15.8 µm deep.
What is sample D?
Sample D (K15-52; Supplementary Fig. S7) is from subrounded 2–4-cm-scale sandstone pebbles within the upper Sixtymile breccia that fills steep-walled channels on Nankoweap Butte about 56 m above the base of the section (Supplementary Fig. S12 ). Its detrital zircon spectrum (Fig. 1) has a few pre-1,800 Ma grains, prominent modes at 1,690 and 1,428 Ma, smaller modes at 1,210 and 1,083 Ma and a young grain population of 510.5 ± 7.7 Ma (LA-ICPMS weighted mean age of 17 grains). Five of the young grains were also dated by CA-ID-TIMS and gave concordant and equivalent isotope ratios with a weighted mean U–Pb age of 512.4 ± 0.7 Ma, which provides a reproducible conservative maximum depositional age. One grain gave a concordant date of 508.6 ± 0.8 Ma that we use as a precise maximum depositional age under the assumption that chemical abrasion was effective in removing any Pb-loss domains. Lower Th/U values for this grain compared with the 512 Ma grains also supports its unique provenance (Supplementary Table S2 ). Thus, CA-ID-TIMS analysis confirms the results of LA-ICPMS, but resolves two discrete ages within the Cambrian population and thus refines the stratigraphic interpretation. Sample E is a composite of three samples from maroon sandstones near the top of the exposed Sixtymile Formation at Nankoweap Butte (K06-13, K10-53 and K12-100; Supplementary Fig. S8 ). The detrital zircon spectrum ( n = 228; Fig. 1) is dominated by modes at 1,722 and 1,441 Ma, with minor modes between 1,180 and 1,030 Ma and no Cambrian grains.
What are the changes in the Earth system?
Neoproterozoic to Cambrian rocks record dramatic changes in Earth systems such as extreme climate changes during Snowball Earth events 1, oxygenation events 2 and the diversification of microbial life leading to animals 3. Steadily improving geochronology is helping to document the interaction of protracted and abrupt events within these entwined systems 4, 5. Rifting of Rodinia has been implicated with these system changes 6, but the timing and duration of rifting remain incompletely understood. Palaeomagnetic data suggest that western Laurentia had separated from adjacent conjugate continents by 750 million years ago (Ma) 7, but geologic data suggest a much longer history of incipient rifting beginning at 780 Ma 8, rift-related shallow seaways during 720–630 Myr glaciations 9 and thermal subsidence in the Cambrian 10, 11.
Where is the Sixtymile Formation?
Below the Great Unconformity, the Sixtymile Formation 20, 24, 25 is exposed in the eastern Grand Canyon along the Chuar syncline, which formed during west-down normal slip on the Butte fault 20 (Supplementary Fig. S1 ). It underlies the Tapeats Sandstone with angular unconformity in places but can be locally disconformable (Supplementary Figs. S2 and S3 ). It includes lacustrine, shallow marine and fluvial units, with numerous landslides or subaqueous slumps in lower units suggesting that its deposition took place in a fault-controlled basin during reactivation of the Butte fault 20, 25. Before this study, the age of the Sixtymile Formation was bracketed by the 729.0 ± 0.9 Ma ash of the underlying Chuar Group 26 and 515–507 Ma Bolbolenellus euryparia to Glossopleura walcotti Zone trilobites of the overlying Bright Angel Shale 27, 28.
What strata record the transgressive inundation of many continents by advancing oceans that deposited sheet?
Cambrian strata globally record the transgressive inundation of many continents by advancing oceans that deposited sheet sands, muds and carbonates 12. In Laurentia, the term Sauk sequence was applied 13 and was envisioned as a cumulative transgression across the basement unconformity that may have lasted from the Neoproterozoic near the rift margins to the Early Ordovician in the mid-continent. This prolonged sedimentary onlap took place in pulses, each followed by sedimentary offlap, such that the Sauk 'megasequence' 14 is bounded by and includes important internal unconformities. The timescale linking Cambrian unconformities, extinctions and global change 15, 16 is a globally important subject that needs refinement.
What is the ID-TIMS age of zircon?
The primary standard consists of fragments of a single large zircon crystal (SL-2) with an ID-TIMS age of 563.5 ± 3.2 Ma (2σ). In-run analyses of these fragments are conducted every fifth measurement and the results are used to correct for interelement fractionation of Pb/U. For these particular analyses, the uncertainty resulting from this calibration correction is between 0.8 and 1.4% (2σ) for both 206 Pb/ 238 U and 206 Pb/ 207 Pb. Concentrations of U and Th are calibrated relative to measurements of SL-2, which contains ~518 ppm U and ~68 ppm Th.
When did Laurentia separate from Rodinia?
Palaeomagnetic studies suggest early separation of western continents from Rodinia by 750 Ma 7 , but age, geometry and areal extent of strata west of the Cordilleran hingeline 9, 44 indicate continued 750–600 Myr basin deposition. The extraordinary amount of time recorded by these interpreted rift basins is challenging to explain mechanistically as drift-phase thermal subsidence does not readily explain multiple sedimentary onlaps 10, 11 and drift-phase subsidence is typically observed to lag initial development of rift basins (for example, during Mesozoic rifting of eastern Pangea) by only 65–45 Myr, not hundreds of millions of years 45. Models involving more than one continental separation along western Laurentia are possible, with Cambrian final separation following Neoproterozoic failed rift episodes 43. But none of these models have been unequivocally supported palaeomagnetically or geologically, meaning that conjugate continents to western Laurentia and rift timing remain in dispute.
How can the Great Unconformity and Sauk Megasequence be explained?
The Great Unconformity and Sauk Megasequence, plus the later planation surfaces, can be explained by Flood catastrophic processes. A possible model for the formation of these features follows. The early Flood unleashed the mechanism of the Flood, which I think was caused by impacts. 9 The very early Flood should be the most catastrophic part of the Flood, and with multiple impacts very strong currents and turbulence would occur. Such a mechanism 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
How long did the Great Unconformity last?
The uniformitarian scientists claim that the Great Unconformity represents a long period of continental denudation, well over a billion years at many locations. This is in the context of attempting to explain the evolution of biomineralization by means of the geochemical effects of prolonged continental weathering and denudation. 6 However, erosion does not form planation surfaces today, except locally when a river floods and erodes its banks. 7 Planation surfaces are being destroyed by present-day erosion, especially by running water that forms channels and valleys. Geomorphologist C.H. Crickmay states:
What is the Great Unconformity?
The Great Unconformity, first defined in the Grand Canyon in 1869, separates the Cambrian Tapeats Sandstone from the underlying Precambrian rocks (the geological column and timescale are used for discussion purposes only). There is some confusion in the Grand Canyon in that there is a second major unconformity between the Precambrian sedimentary rocks and the igneous and metamorphic rocks (figure 1). The uniformitarian origin of the Great Unconformity is supposed to be slow denudation over about a billion years that resulted in a nearly flat planation surface. Then after this denudation, a shallow marine transgression deposited the Tapeats Sandstone, Bright Angel Shale, and Muav Limestone in a fining upward sequence called the Tonto Group.
What type of sedimentary rocks were deposited in the Rocky Mountains?
Once the thick Paleozoic and Mesozoic sedimentary rocks were deposited in the Rocky Mountains region, great differential uplift ( Psalm 104:8) occurred in the Cenozoic to form the current high mountains and deep basins filled with thick sedimentary rocks. 13 For instance, the Uinta Mountains of northeast Utah rose up 12 km relative to the adjacent basins during the Cenozoic. 14 That is why the Great Unconformity is low down in the Grand Canyon but located at the tops of mountains in Wyoming and Montana. The thick sedimentary rocks were greatly eroded from off many of the ranges in the Rocky Mountains and Colorado Plateau with some of the eroded debris continuing to fill up the valleys and basins of the Rocky Mountains and being transported off the continent to form the continental shelves. 15, 16 This is the time when the continents were greatly eroded, forming planation surfaces with tall erosional remnants during sheet flow erosion, and pediments, water and wind gaps, deep canyons, and valleys during channelized erosion. 13, 17
Why do geologists believe their eyes and stretch the deposition of this 600-m thick sequence into 200 Ma?
However, the geologists do not believe their eyes and stretch the deposition of this 600-m thick sequence into 200 Ma because of their stretched-out timescale. Such great time injected between the layers makes no sense based on present day erosional patterns that can erode all the continents to sea level in a few tens of millions of years. Based on erosion today, which is an application of the uniformitarian principle, the data do not support such long time periods subjectively interjected within the sedimentary rocks.
What is the Sauk Megasequence?
It is believed to represent a continental transgression of the sea but seems contradictory in that the fining upward sequence is so widespread over large areas. A rising sea level in such a transgression would be expected to produce a more chaotic distribution of sediments with much conglomerate over short lateral and vertical spatial scales —unlike the Sauk Megasequence.
What is the absaroka mountain?
The Absaroka Mountains represent volcanic breccia flows , called the Absaroka Volcanics, that have piled up about 1,800 m deep over an area of 23,000 km 2 and contain multiple levels of vertical petrified trees at numerous locations. 4 They are dated Eocene, which is early Cenozoic, within the uniformitarian geological column.
How was Cambrian sandstone distributed?
7. Based on various lines of evidence preserved in the rock record, Cambrian sandstone appears to have first been distributed by wind and rivers. The Sauk transgression that followed caused marine reworking of much of that sand.
What are the sediments that indicate the Cambrian period?
4. Extensive sequences of Cambrian marine sediments (sandstone, shale & fossil-bearing limestone) indicate that the continents were at times flooded by great shallow seaways. North America was almost completely drowned in Late Cambrian time by what came to be known as the Sauk transgression.
What continents were barren and devoid of vegetation?
The Cambrian continents were barren and devoid of all vegetation. The lifeless, barren landscape was blanketed by blowing sand, silt and clay. Cratons were low in relief and characterized by broad, gentle warping of the crust. 4.
What type of deposits are found in North America during the Cambrian era?
8. The occurrence of Cambrian oolites, shelly limestone and local evaporite deposits suggest a warm climate for North America during this period.
What type of rock was flooded by the Cambrian seas?
6. Mature quartz sandstone derived from deep continental weathering and wind erosion, were flooded by invading seas and reworked into broad sheet-like deposits. Extensive marine deposits indicate that the Cambrian seas flooded a barren continental surface of very low relief.
What happened during the late Proterozoic?
1. During the late Proterozoic, the global supercontinent began to break up so that by early Cambrian time, all the continental fragments were surrounded by slowly subsiding passive margins. 2.
What type of sediments did continental interiors experience?
The subsiding margins of continents, on the other hand, accumulated thick packages of shallow marine sediment.
What are the sedimentary loss sequences of North America?
Sedimentary “Sloss” Sequences of North America. In the Mid-Atlantic region, the Sauk, Tippecanoe, and Kaskaskia are well exposed. White and yellow areas represent major marine transgressions onto the craton while black areas represent major unconformities (sequence boundaries). The Sauk is bounded on the bottom by the “Great Unconformity”, the boundary between the Sauk and Tippecanoe is referred to as the “Knox Unconformity”, and the boundary between the Tippecanoe and Kaskaskia is the “Wallbridge Unconformity”. All six of Sloss’ Sequences are 2nd order supercycles. (Sloss, 1964)
How did the Taconian Mountains form?
Eventually, the Taconian Mountains formed off of the coast an arc of Japan-like volcanic islands. Evidence for this is contained within the lithostratigraphic record as widespread and in many cases very thick volcanic ash deposits. While the entire sequence is transgressive across the craton, tectonic change and sedimentation changes taking place due to the process of orogeny along the southern portion of the craton would lead to more localized changes. Relative sea level, sedimentation, and tectonics would lead to lower orders of sea level sequences (3rd and higher). Embedded within the Tippecanoe as a whole then are successively smaller sequences of shorter duration that record events taking place throughout this time period.
What are the four sequences of sea level transgressions?
The youngest two, the Kaskaskia and Absaroka, record the closing of the Iapetus Ocean Basin. In between these and the Sauk exists the Tippecanoe Sequence. Based upon sediment thickness and volume alone, it is likely that this transgression was the deepest of all of them in terms of water depth. It also records the evolution of the ancient Taconian Mountains.
What is the boundary between the Sauk and Tippecanoe?
The Sauk is bounded on the bottom by the “Great Unconformity”, the boundary between the Sauk and Tippecanoe is referred to as the “Knox Unconformity”, and the boundary between the Tippecanoe and Kaskaskia is the “Wallbridge Unconformity”. All six of Sloss’ Sequences are 2nd order supercycles.
Where is the Taconian Island arc?
Note the position of the Paleoequator. The Taconian Island arc is still off of the southern coast of Laurentia (modern eastern North America) and the Tippecanoe Sea lies to its north (forearc basin). Sediments deposited in the forearc basin include the early Tippecanoe Carbonates into the Martinsburg Formation.
What order are all six sequences in the Sloss sequence?
All six of Sloss’ Sequences are 2nd order supercycles. (Sloss, 1964) In 1963, a geologist named Lawrence Sloss from Northwestern University would become famous because of a paper published as a part of a symposium held by the Kansas Geological Survey and collectively published in KGS Bulletin 169.
What oceans did the North American craton see?
During this time, the North American craton would see the opening and closing of the proto-Atlantic Ocean (Iapetus Ocean), plate movement from southern subtropical latitudes to tropical latitudes, and the coming and going of epicontinental epeiric seas. The rock record in this region is diverse and important.
What is the Tippecanoe sequence?
Tippecanoe sequence. The Tippecanoe sequence was the cratonic sequence --that is, the marine transgression --that followed the Sauk sequence; it extended from roughly the Middle Ordovician to the Early Devonian .
What was the Tippecanoe transgression?
The Tippecanoe transgression ended this period of erosion, beginning with the deposition of clean sandstones across the craton, followed by abundant carbonate deposition. In the east these carbonates gradually become shales, representing sediments eroded from highlands created in the Taconic orogeny. The Tippecanoe sequence may have been the ...
Why did the craton of the Ordovician erode?
After the regression of the Sauk Sea early in the Ordovician, the exposed craton for a time underwent vigorous erosion, due to being located in a tropical climate; indeed, at this point in the Paleozoic the North American continent roughly straddled the equator.
Which sequence ended with a regression in the early Devonian?
The Tippecanoe sequence ended with a regression in the early Devonian, to be followed later by the Kaskaskia sequence .
Which Paleozoic period was the Tippecanoe sequence?
The Tippecanoe sequence may have been the deepest of the Paleozoic. At one point during the Silurian period, the Taconic highlands—which later became the Appalachian Mountains --were the only part of North America that was not submerged.