The Sauk sequence was the earliest of the six cratonic sequences that have occurred during the

Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when anima ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. It was followed by the Tippecanoe, Kaskaskia, Absaroka, Zuñi, and Tejas sequences. The sequence dates from the late

Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...

through the early Ordovician periods, though the marine transgression did not begin in earnest until the middle

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

.Monroe, JS, and R Wicander (1997) ''The Changing Earth: Exploring Geology and Evolution,'' 2nd ed. Belmont: West Publishing Company, 1997. pp. 533–534 It is one of the most striking cratonic sequences in the geological record, spreading sheets of sandstone across

basement rock In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The baseme ...

deep into the interiors of many continents. The transgression took place rapidly, advancing over across the

Grand Canyon The Grand Canyon (, yuf-x-yav, Wi:kaʼi:la, , Southern Paiute language: Paxa’uipi, ) is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is long, up to wide and attains a depth of over a m ...

region in less than five million years. At its peak, most of

was covered by the shallow Sauk Sea, save for parts of the

Canadian Shield The Canadian Shield (french: Bouclier canadien ), also called the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the anc ...

and the islands of the Transcontinental Arch. The

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

of the Sauk sequence indicates shallow-water deposition, primarily consisting of well-sorted sandstones and

clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

carbonates. A marine regression ended the Sauk sequence early in the Ordovician, to be followed by the Tippecanoe sequence later in the period. The transgression is attributed to thermal subsidence following the breakup of the supercontinent of

Rodinia Rodinia (from the Russian родина, ''rodina'', meaning "motherland, birthplace") was a Mesoproterozoic and Neoproterozoic supercontinent that assembled 1.26–0.90 billion years ago and broke up 750–633 million years ago. were probably ...

, combined with a rise in global sea level due to climate change or shifts in global tectonics.

References

Proterozoic geology Cambrian North America Ordovician North America Ediacaran United States Cambrian United States Ordovician United States Ediacaran stratigraphic units of North America {{US-geology-stub