Ludfordian

In the geologic timescale, the Ludfordian is the age of the Ludlow epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that occurred between 425.6 ± 0.9Ma and 423. ± 2.3 Ma (million years ago). The Ludfordian age succeeds the Gorstian age and precedes the Pridoli epoch. It is named for the village of Ludford in Shropshire, England.

Epochs in the Silurian

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Epochs of the Silurian Period.
Axis scale: millions of years ago.

The Lau event is a rapid pulse of cooling during the Ludfordian, about 424 million years ago; it is identified by a pulse of extinctions and oceanic changes. It is one of the series of fast sea-level and excursions in oxygen isotope ratios that signal fast switches between warm and cold climate states, characteristic of the Silurian climatic instability. The Lau Event occurred during an extended period of elevated seawater saturation state, explained by reservoirs of the planet's fresh water being locked up in massive polar ice caps. The sudden reappearance in normally saline marine environments of stromatolites and a mass occurrence of oncoids during the event suggested that minor extinction events like the Lau Event also resulted in periods of reduced grazing pressures on surviving "disaster biota", which can be compared to the aftermath of the more catastrophic end-Ordovician and end-Permian mass extinctions.[3]

Palaeontology

Arthropods

Arthropods of the Ludfordian
Taxa	Presence	Location	Description	Images
Brontoscorpio		Trimpley, Worcestershire, UK

Plants

Plants of the Ludfordian
Taxa	Presence	Location	Description	Images
Chaetocladus capitatus		Cornwallis Island, Northern Canada[4]
Eocladus		Cornwallis Island, Northern Canada[4]

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gollark: ```python#!/usr/bin/env python3import argparseimport subprocessparser = argparse.ArgumentParser(description='Compile a WHY program')parser.add_argument("input", help="File containing WHY source code")parser.add_argument("-o", "--output", help="Filename of the output executable to make", default="./a.why")parser.add_argument("-O", "--optimize", help="Optimization level", type=int, default="0")args = parser.parse_args()def build_C(args): template = """#define QUITELONG long long intconst QUITELONG max = @max@;int main() { QUITELONG i = 0; while (i < max) { i++; } @code@} """ for k, v in args.items(): template = template.replace(f"@{k}@", str(v)) return templateinput = args.inputoutput = args.outputtemp = "ignore-this-please"with open(input, "r") as f: contents = f.read() looplen = max(1000, (2 ** -args.optimize) * 1000000000) code = build_C({ "code": contents, "max": looplen }) with open(temp, "w") as out: out.write(code)subprocess.run(["gcc", "-x", "c", "-o", output, temp])```

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References

Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.
Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.
M. Calner, "A Late Silurian extinction event and anachronistic period" Geology 33, pp. 305–308; Geology On-line Forum: response to a reply.
Steven T. LoDuca, Michael J. Melchin & Heroen Verbruggen (2011). "Complex noncalcified macroalgae from the Silurian of Cornwallis Island, Arctic Canada" (PDF). Journal of Paleontology. 85 (1): 111–121. doi:10.1666/10-025.1. Archived from the original (PDF proofs) on 2011-07-22.

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[Jeppsson2007-1] Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.

[Munnecke2003-2] Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.

[3] M. Calner, "A Late Silurian extinction event and anachronistic period" Geology 33, pp. 305–308; Geology On-line Forum: response to a reply.

[Complex-4] Steven T. LoDuca, Michael J. Melchin & Heroen Verbruggen (2011). "Complex noncalcified macroalgae from the Silurian of Cornwallis Island, Arctic Canada" (PDF). Journal of Paleontology. 85 (1): 111–121. doi:10.1666/10-025.1. Archived from the original (PDF proofs) on 2011-07-22.