Aeronian | |||||||||||||
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Chronology | |||||||||||||
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Etymology | |||||||||||||
Name formality | Formal | ||||||||||||
Usage information | |||||||||||||
Celestial body | Earth | ||||||||||||
Regional usage | Global (ICS) | ||||||||||||
Time scale(s) used | ICS Time Scale | ||||||||||||
Definition | |||||||||||||
Chronological unit | Age | ||||||||||||
Stratigraphic unit | Stage | ||||||||||||
Time span formality | Formal | ||||||||||||
Lower boundary definition | FAD of the graptolite Monograptus austerus sequens | ||||||||||||
Lower boundary GSSP | Trefawr Track Section, Llandovery, Wales, UK 52°01′48″N 3°42′00″W / 52.0300°N 3.7000°W | ||||||||||||
Lower GSSP ratified | 1984[4] | ||||||||||||
Upper boundary definition | Just above LAD of the brachiopod Eocoelia intermedia, below FAD of lowest succeeding species Eocoelia curtisi | ||||||||||||
Upper boundary GSSP | Cefn-cerig Road Section, Llandovery, Wales, UK 51°58′12″N 3°47′24″W / 51.9700°N 3.7900°W | ||||||||||||
Upper GSSP ratified | 1984[4] |
In the geologic timescale, the Aeronian is an age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that began 440.8 ± 1.2 Ma and ended 438.5 ± 1.1 Ma (million years ago). The Aeronian Age succeeds the Rhuddanian Age and precedes the Telychian Age, all in the same epoch.[5]
During the Aeronian the Sedgwickii Event occurred in which graptolite diversity was greatly reduced.[6] This event has been attested in locations such as today's Canada, Libya as well as in La Chilca Formation in Argentina (then part of Gondwana).[6]
The GSSP is located in the Trefawr Track section, 500m north of Cwm-coed-Aeron Farm, Wales, UK.[7] The GSSP lies within the gently-dipping blocky mudstones of the Trefawr Formation, which principally yield abundant and diverse shelly faunas, but also contain enough graptolites to allow recognition of several biozones.[8]