Elements used in absolute dating
4,540,000,000 (4.54 billion) years ago Formation of planet Earth - Usher's date was ).Archeozoic: end of Azoic to 2,500,000,000 years ago: The era of the earliest living beings on earth.starting about 2.500,000,000 years ago, sedimentary rocks affected by higher amounts of oxygen in the atmosphere, appear red, as though rusted. Fossils include earliest fish, but of types very different from modern ones. signs of the "tentative presence" of plants on land.Mesoproterozoic from 1,600,000,000 to 1,000,000,000 years ago. Particular importance attaches to occurred around 1,300,000,000 years ago during the late Mesoproterzoic era, after the earth's transition to a more highly oxygenated atmosphere with an ozone screen. Deposits that made Westmorland Green slate formed around 450 million years ago. About 50 million years later, the material was altered by heat and pressure (metamorphosed) to slate, during mountain-building. After many more millions of years, they resembled patches of moss a few centimeters high.This was not adopted, but his division into Mississippian, for the 's "Story of a piece of coal" focuses on coal formation, but includes a section on the carboniferous limestone.
Henry Shaler Williams (1891) proposed Pennine System as the name for the Carboniferous.
"More than 3.5 billion years ago, small single-celled organisms acquired the capacity to photosynthesize" "Plants were restricted to the aquatic world until three billion years later, the first uncontroversial evidence for life is found 2,700,000,000 years ago.
The reference relates to sulphate and iron reduction as early forms of microbial respiration.
Three strata of toadstone had been found, and the limestone under the third was as far as miners had reached. The map project describes the "shallow tropical sea surrounded by coral reefs" in which the limestones were laid down and how "subterranean volcanoes erupted spasmodically through the sea floor, covering the limestones with ash and lava" which formed the toadstone.
is Galena (lead sulfide) formed as pockets or veins in carbonate rock into which the mineral bearing fluid rock has intruded.
The end-Frasnian extinction (the largest) about 375 million years ago.