Sauk sequence
Encyclopedia
The Sauk sequence was the earliest of the six cratonic sequence
s that have occurred during the Phanerozoic
(followed by the Tippecanoe
, Kaskaskia
, Absaroka
, Zuñi
, and Tejas
). It dates from the late Proterozoic
through the early Ordovician
, though the marine transgression
did not begin in earnest until the middle Cambrian
.
At its peak, most of North America
was covered by the shallow Sauk Sea, save for parts of the Canadian Shield
and the islands of the Transcontinental Arch. The stratigraphy
of the Sauk sequence indicates shallow-water deposition, primarily consisting of well-sorted sandstone
s and clastic carbonate
s.
A marine regression ended the Sauk sequence ended early in the Ordovician, to be followed by the Tippecanoe sequence
later in the period.
Cratonic sequence
A cratonic sequence refers to a very large-scale lithostratographic sequence that covers a complete marine transgressive-regressive cycle across a craton...
s that have occurred during the Phanerozoic
Phanerozoic
The Phanerozoic Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 542 million years and goes back to the time when diverse hard-shelled animals first appeared...
(followed by the Tippecanoe
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.-Sedimentary characteristics:...
, Kaskaskia
Kaskaskia sequence
The Kaskaskia sequence was a cratonic sequence that began in the mid-Devonian, peaked early in the Mississippian, and ended by mid-Mississippian time...
, Absaroka
Absaroka sequence
The Absaroka sequence was a cratonic sequence that extended from the end of the Mississippian through the Permian periods. It is the unconformity between this sequence and the preceding Kaskaskia that divides the Carboniferous into the Mississippian and Pennsylvanian periods in North America.Like...
, Zuñi
Zuñi sequence
The Zuñi sequence was the major cratonic sequence after the Absaroka sequence that began in the latest Jurassic, peaked in the late Cretaceous, and ended by the start of the following Paleocene...
, and Tejas
Tejas sequence
The Tejas sequence was the last major marine transgression across the North American craton. Following the late Cretaceous regression that ended the Zuñi sequence, the oceans advanced again early in the Cenozoic, peaking during the Paleocene and Eocene epochs...
). It dates from the late Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
through the early Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
, though the marine transgression
Transgression (geology)
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water...
did not begin in earnest until the middle Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
.
At its peak, most of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
was covered by the shallow Sauk Sea, save for parts of the Canadian Shield
Canadian Shield
The Canadian Shield, also called the Laurentian Plateau, or Bouclier Canadien , is a vast geological shield covered by a thin layer of soil that forms the nucleus of the North American or Laurentia craton. It is an area mostly composed of igneous rock which relates to its long volcanic history...
and the islands of the Transcontinental Arch. The stratigraphy
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
of the Sauk sequence indicates shallow-water deposition, primarily consisting of well-sorted sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s and clastic carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
s.
A marine regression ended the Sauk sequence ended early in the Ordovician, to be followed by 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.-Sedimentary characteristics:...
later in the period.