| System (period) | Series | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Devonian | Lower | Lochkovian | 419.2±3.2 | |
| Silurian | Pridoli |  423.0±2.3
| ||
| Ludlow | Ludfordian | 425.6±0.9
| ||
| Gorstian | 427.4±0.5
| |||
| Wenlock | Homerian | 430.5±0.7
| ||
| Sheinwoodian | 433.4±0.8
| |||
| Llandovery | Telychian | 438.5±1.1
| ||
| Aeronian | 440.8±1.2
| |||
| Rhuddanian | 443.8±1.5
| |||
| Ordovician | Upper | Hirnantian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Ludlow is a third series of the Silurian system, corresponding to the Ludlow epoch of the Silurian period. It began after the Homerian age of the Wenlock at 427.4 ± 0.5 Ma (million years ago) and lasted until the Pridoli at 423.0 ± 2.3 Ma (IUGS 2023). During this epoch, there was a change in the species composition of sea bottom inhabitants.
Definition[]
The Global Stratotype Section and Point (GSSP) of the Ludlow series and the Gorstian stage was ratified in 1980. The beginning of the epoch is related to the first appearance of the graptolite species Saetograptus (Colonograptus) varians, which is also coincident with the base of the Lower Elton Formation. The type section is located near Ludlow, UK.[2]
Subdivisions[]
The Ludlow divided into two stages: Gorstian and Ludfordian. In geochronology, both correspond to the same ages.
Paleogeography[]
During Ludlow, the merger of Baltica (modern northern Europe and western Russia) and Laurentia (North America and Greenland) began, leaving the Iapetus Ocean as a narrow gulf between them and closed in the northern part. As a result of the collision of continents, mountains rose on the eastern coast of Laurentia. This process is known as the Acadian orogeny. Siberia was approaching Laurentia and the Baltic from the northeast. The largest continent remained Gondwana, which drifted around the south pole. Vast coastal zones of all continents covered shallow seas.
Climate[]
A warm climate persisted throughout the Ludlow, although southern Africa probably contained the last glaciers from the late Ordovician. Over the course of the epoch, the amount of oxygen in the atmosphere increased, which contributed to the development of terrestrial ecosystems. However, carbon dioxide levels remained very high.
Ludlow life[]
Oceans[]
Ateleaspis
The shallow seas contained numerous crinoids, suspension-feeding brachiopods (Lissatrypa, Molongia, Atrypa, Lingula) and bivalves (Buchiola, Dualina, Slava), as well as burrowing trilobites and worms. Ainiktozoon, a strange crustacean, is known from the Ludlow of the Patrick Burn Formation in Scotland. Eurypterids (Eurypterus, Mixopterus, Pterygotus, Pittsfordipterus) and straight-shelled cephalopods (Orthoceras, Michelinoceras) hunted in the water column. The variety of vertebrates increased. Numerous jawless fishes like Lanarkia, Thelodus, Birkenia and Ateleaspis fed on the coastal shallows. The diversity of jawed fish has increased markedly, and the earliest placoderms (Silurolepis) appeared anomg them.
In the middle of the Ludfordian, the Lau Event occurred as a result of which some conodonts, graptolites and brachiopods became extinct. The exact reasons for this extinction are unknown.
Land[]
The number of land plants and, according to several researchers, fungi gradually increased. The plants remained stunted, and there were no tree forms yet. Baragwanathia, a land plant with possibly the earliest known leaves, existed in this epoch.[3] Primitive centipedes fed on plants, and the main land predators were scorpions. Perhaps early insects and some gastropods lived on land with them.
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Paleozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=77.
- ↑ "Ludlow Epoch: Evidence of earliest leaves". https://sites.google.com/site/paleoplant/geologic/phanerozoic/paleozoic/silurian/ludlow.