HOME

TheInfoList




The Tonian (from grc, τόνος, tónos, meaning "stretch") is the first
geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth sciences, Earth scientists to describe t ...
of the
Neoproterozoic The Neoproterozoic Era is the unit of geologic time The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such ob ...
Era An era is a span of time defined for the purposes of chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging t ...
. It lasted from to Mya (million years ago). Instead of being based on
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 ...

stratigraphy
, these dates are defined by the
ICS ICS may refer to: Computing * Image Cytometry Standard, a digital multidimensional image file format used in life sciences microscopy * Industrial control system, computer systems and networks used to control industrial plants and infrastructure ...
based on radiometric chronometry. The Tonian is preceded by the
Stenian The Stenian Period (from grc, στενός, stenós, meaning "narrow") is the final geologic period in the Mesoproterozoic era (geology), Era and lasted from annum, Mya to Mya (million years ago). Instead of being based on stratigraphy, these da ...
Period of the
Mesoproterozoic The Mesoproterozoic Era is a geology, geologic era (geology), era that occurred from . The Mesoproterozoic was the first period of Earth's history of which a fairly definitive geological record survives. Continents existed during the preceding era ...
Era and followed by the
Cryogenian The Cryogenian (, from grc, κρύος, krýos, meaning "cold" and , romanized: , meaning "birth") is a geologic period that lasted from . It forms the second geologic period of the Neoproterozoic era (geology), Era, preceded by the Tonian Perio ...
.
Rifting In geology Geology (from the γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is a branch of concerned with both the liquid and , the of which it is composed, and the processes by which they change over ...
leading to the breakup of
supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...
Rodinia Rodinia (from the Russian родить, ''rodit'', meaning "to beget, to give birth", or родина, ''rodina'', meaning "motherland, birthplace") was a Neoproterozoic supercontinent that assembled 1.1–0.9 billion years ago and broke up 750 ...

Rodinia
, which had formed in the mid-Stenian, occurred during this period, starting from 900 to 850 Mya.


Biology

The first putative metazoan (animal) fossils are dated to the middle to late Tonian ( 890-800 Mya). The fossils of ''
Otavia antiqua
Otavia antiqua
'', which has been described as a sponge by its discoverers and numerous other scholars, date back to about 800 mya. Even earlier sponge-like fossils have been reported in reefs dating back to 890 million years before the present, but their identity is highly debated. This dating is consistent with molecular data recovered through genetic studies on modern metazoan species; more recent studies have concluded that the base of the animal
phylogenetic tree A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree (graph theory), tree showing the evolutionary relationships among va ...

phylogenetic tree
is in the Tonian. The first large
evolutionary radiation An evolutionary radiation is an increase in taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific class ...
of
acritarch Acritarchs are organic microfossils, known from approximately 1800 million years ago to the present. Their diversity reflects major ecological events such as the appearance of predation and the Cambrian explosion. Definition Acritarchs were ori ...
s occurred during the Tonian.


See also

*


References


Further reading

* * *01 Geological periods Proterozoic geochronology {{geochronology-stub