Dbk: Created page with "By Ian Wilkinson When we speak about geological time, we refer to hundreds or even thousands of millions of years – vast periods of time. To aid in our understanding of th..."

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Created page with "By Ian Wilkinson When we speak about geological time, we refer to hundreds or even thousands of millions of years – vast periods of time. To aid in our understanding of th..."

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By Ian Wilkinson

When we speak about geological time, we refer to hundreds or even thousands of millions of years – vast periods of time. To aid in our understanding of this long timeline, the time equivalents of the rocks are divided up into a number of eras and periods each of which is given a name. Perhaps the most famous is the Jurassic featured in the film “Jurassic Park”. Absolute ages can be assigned to these eras and periods by a number of methods, including the measurement of radioactive decay of certain minerals. This Pathfinder moves through geological time explaining Britain’s environment at each time-slice and showing examples of the animal or plant life fossilised in the rock succession.

{|class="wikitable"
|-
|Era
|Fossil
|Millions of years
|Period/subperiods
|-

|Cainozoic
|[[File:P549448.jpg|thumb|A Pleistocene bivalve, Pholas, preserved in its burrow.P549448]]
|0-2
|Quaternary (Holocene and Pleistocene epochs): Rapid climatic cooling which had begun in the Neogene continued into the Pleistocene, when four major glaciations occurred. During periods of ice retreat, the climate was quite warm and animals such as mammoths, ‘Irish Elk’, woolly rhinoceras, hyenas, bears, wolves and even hippopotamus and lions migrated to Britain (Britain was connected to mainland Europe due to the fall in sea level). Eventually humans reached Britain, the earliest species being Homo erectus. Around the coasts of Britain, marine sediments dating to this time are found. Fossils include bivalves, gastropods, fish, ostracods, brachiopods and echinoids. Britain during the Holocene times (the last 10 thousand years), has been mainly free from ice.
|-
|Cainozoic
|[[File:P549520.jpg|thumb|A Pliocene coral, Flabellum woodi, that lived in the North Sea. P549520]]
|2-3
|Neogene (Pliocene and Miocene epochs): The Miocene was a time of cooling and the evolution and spread of grasslands, steppes and savannas. However, withdrawal of the sea during Miocene times has left a gap in the succession in Britain (there are one or two small patches of rock that may be of this age and they are known to occur in the North Sea and off northern Scotland). In Britain the Neogene is represented by shallow marine Pliocene rocks (1.8 to 5 million years old). Those in East Anglia contain corals, bryozoa, bivalves, gastropods, terebratulids, brachiopods and ostracods.
|-
|Cainozoic
|[[File:P550283.jpg|thumb|The Oligocene gastropod, Filholia elliptica, from the Isle of Wight. P550283]]
|23-34
|Late Palaeogene (Oligocene epoch): In the Isle of Wight shallow marine conditions were sometimes replaced by freshwater environments. Pulmonate gastropods such as Planorbina, Galba and Filholia are often found, and leaves and insects may also be present.
|-
|Cainozoic
|[[File:P549463.jpg|thumb|An Eocene leaf of Lauracaea, from Southern England. P549463]]
|34-65
|Early Palaeogene (Eocene and Palaeocene epochs) : Palaeocene and Danian rocks do not occur in Britain, although they both occur offshore. Rocks of Eocene age (34-55 million years old) are best preserved in southern England. Here shallow marine clays contain fossil plants such as mangroves on the coast, pines, cinnamon, ferns and flowering plants such as magnolia and blackberry. Reptiles like crocodiles lived in the warm waters, birds are occasionally found and invertebrate fossils abound including bivalves and gastropods. By the close of the Eocene, cooler climatic conditions were starting to be felt.
|-
|Cainozoic
|[[File:P550271.jpg|thumb|A late Cretaceous echinoid, Temnocidaris sceptrifera.P550271]]
|65-99
|Late Cretaceous: This was a period characterised by the Chalk of Britain. Over 90% of this very pure limestone comprises the skeletons of microscopic single-celled algae. However many other marine organisms are also found, including echinoids, crinoids, ammonites, belemnites, bivalves and gastropods, together with a number of crustaceans and fish (including the coelocanth Macropoma). However, the end of the Cretaceous saw the extinction of the Dinosaurs, ammonites, belemnites, and most of the large marine reptiles.
|-
|Cainozoic
|[[File:P549465.jpg|thumb|An early Cretaceous fern, Cladophlebis, that lived in the Wealden woodlands. P549465]]
|99-142
|Early Cretaceous: The Wealden woodlands covered southern England at this time. Cycads, conifers and treeferns abound and small ferns, horsetails, clubmosses and liverworts form the undergrowth. Flowering plants began to evolve at this time, although none has been recognised in Britain. It was in this area that most of the dinosaurs of Britain have been recorded. In the north, sediments yield early Cretaceous ammonites, bivalves, ostracods and other marine organisms. By Aptian and Albian times (??? million years ago, the land of southern England had been covered by the sea.
|-
-
|Cainozoic
|[[File:P549559.jpg|thumb|A late Jurasic ammonite, Rasenia uralensis.P549559]]
|142-205
|Jurassic: Beginning in the latest Triassic and throughout most of the Jurassic, much of Britain was submerged beneath the sea. Islands formed during the mid-Jurassic in places and plants (including ginkgos) and dinosaur remains are found. The Jurassic is characterised more by its marine animals including the newly evolved ammonites, brachiopods, bivalves, crinoids, fish and marine reptiles. The extinction of the Palaeozoic rugose and tabular corals had taken place at the end of the Permian, and newly evolved scleractinian corals began to proliferate and build reefs.
|-
|Cainozoic
|
|205-290
|Permo-Triassic: This was a time when most of Britain was land. Britain had moved further north away from the equator where its climate became arid. Although fish, reptilian footprints and plant spores are found in different parts of the rock sequence, compared to the Palaeozoic and Jurassic this was a time of few fossils. Elsewhere mass extinction events saw the disappearance of trilobites, rugose and tabulate corals and many other groups of animal. In Triassic times dinosaurs and mammals evolved.
|-
|Cainozoic
|[[File:P549466.jpg|thumb|A late Carboniferous seed fern, Neuropteris. P549466]]
|290-316
|Late Carboniferous: Britain was on the equator where the climate was humid. The basins in which the marine animals proliferated in the early Carboniferous were filled by sands and muds as the rivers created massive deltas. The earliest forests grew here with giant clubmosses and horsetails; ferns, tree ferns and seed ferns; and in the drier areas, conifers. It is from this forest that Britain’s coal formed. Large insects and spiders inhabited the forests, amphibians lived on the waterside and the first reptiles had evolved (Westlothiana from East Kirkton, Scotland).
|-
|Cainozoic
|[[File:P549523.jpg|thumb|An early carboniferous coral, Siphonodendron junceum, from Ecclefechan, Scotland.P549523]]
|316-354
|Early Carboniferous: Much of southern Britain was covered by a warm tropical sea in which corals, brachiopods, crinoids, gastropods etc. lived with a variety of fish. This was the time when the last of the dendroid graptolites eventually went into extinction.
|-
|-
|Cainozoic
|[[File:P550306.jpg|thumb|A Devonian lungfish, Dipterus, from northern Scotland.P550306]]
|354-417
|Devonian: Much of Britain was a hot, barren land at this time, although south-western England and parts of Scotland were covered by the sea. Scottish waters were rich in fish including lungfish, whereas goniatites, ostracods, bivalves, brachiopods, corals are found in south-west England. It was during the Devonian that the last of the planktonic graptolites became extinct, although benthic dendroids continued into the early Carboniferous.
|-
|-
|Cainozoic
|[[File:P550304.jpg|thumb|A Silurian crinoid, Periechocrinus from the Welsh Marches.P550304]]
|417-443
|Silurian: This was a time when much of Britain was covered by the sea (Iapetus Ocean). Scotland was separated from England and Wales, and graptolites and trilobites lived in the deep waters. England and Wales were situated near the equator where shallow warm water contained corals, sponges, trilobites, gastropods, brachiopods and crinoids. In the deeper waters, graptolites, straight nautiloids and trilobites lived. In a few places (e.g. Wales) land emerged through the waves and the earliest vascular plants grew. They were small and lacked leaves.
|-
|Cainozoic
|[[File:P549553.jpg|thumb|An Ordovician graptolite, Didymograptus murchisoni.P549553]]
|443-495
|Ordovician: This was a time of continued evolutionary radiation. Trilobites reached their peak of diversity, brachiopods were the dominant form amongst the shelly animals, one of the straight types of nautiloids grew to over 4.5 m. long, a giant of its day, and corals began a phase of diversification. Amongst the planktonic species, graptolites were hugely successful and evolved rapidly. Late in the period, spores of non-vascular plants (distant relatives of moss and liverworts) were just beginning to colonise the land.
|-
|-
|Cainozoic
|[[File:P550301.jpg|thumb|Cambrian triliobite, Paradoxides davidis from Wales.P550301]]
|495-545
|Cambrian: Rocks of this age occur in Scotland, Wales and a few places in England. They are mainly marine sediments, with animals such as trilobites, brachiopods, gastropods and worms. Biomineralisation resulted in shells and skeletons for the first time.
|-Era
Periods/subperiods
|Cainozoic
|[[File:P550159.jpg|thumb|Cambrian triliobite, Paradoxides davidis from Wales.P550159]]
|545 4600
|Late Precambrian: Britain has relatively few Precambrian rocks, but there are river-lain and marine deposits in some places. Although fossil bacteria and rocks known to have formed through the action of bacteria (Banded Ironstone Formations) are known in some parts of the world, there are none known in Britain. However, about 600 million years ago, some of the earliest multi-celled organisms lived in Britain, including soft-bodied sea pens. Burrows are also found.
|-Era
Periods/subperiods

P549448.jpg A Pleistocene bivalve, Pholas, preserved in its burrow
0–2 Millions of years

Quaternary (Holocene and Pleistocene epochs)
Rapid climatic cooling which had begun in the Neogene continued into the Pleistocene, when four major glaciations occurred. During periods of ice retreat, the climate was quite warm and animals such as mammoths, ‘Irish Elk’, woolly rhinoceras, hyenas, bears, wolves and even hippopotamus and lions migrated to Britain (Britain was connected to mainland Europe due to the fall in sea level). Eventually humans reached Britain, the earliest species being Homo erectus. Around the coasts of Britain, marine sediments dating to this time are found. Fossils include bivalves, gastropods, fish, ostracods, brachiopods and echinoids. Britain during the Holocene times (the last 10 thousand years), has been mainly free from ice.

P549520 A Pliocene coral, Flabellum woodi, that lived in the North Sea
2–23 Millions of years

Neogene (Pliocene and Miocene epochs)
The Miocene was a time of cooling and the evolution and spread of grasslands, steppes and savannas. However, withdrawal of the sea during Miocene times has left a gap in the succession in Britain (there are one or two small patches of rock that may be of this age and they are known to occur in the North Sea and off northern Scotland). In Britain the Neogene is represented by shallow marine Pliocene rocks (1.8 to 5 million years old). Those in East Anglia contain corals, bryozoa, bivalves, gastropods, terebratulids, brachiopods and ostracods.
P550283

The Oligocene gastropod, Filholia elliptica, from the Isle of Wight
23–34 Millions of years

Late Palaeogene (Oligocene epoch)

In the Isle of Wight shallow marine conditions were sometimes replaced by freshwater environments. Pulmonate gastropods such as Planorbina, Galba and Filholia are often found, and leaves and insects may also be present.

P549463

An Eocene leaf of Lauracaea, from Southern England
34–65 Millions of years

Early Palaeogene (Eocene and Palaeocene epochs)
Palaeocene and Danian rocks do not occur in Britain, although they both occur offshore. Rocks of Eocene age (34-55 million years old) are best preserved in southern England. Here shallow marine clays contain fossil plants such as mangroves on the coast, pines, cinnamon, ferns and flowering plants such as magnolia and blackberry. Reptiles like crocodiles lived in the warm waters, birds are occasionally found and invertebrate fossils abound including bivalves and gastropods. By the close of the Eocene, cooler climatic conditions were starting to be felt.
P550271

A late Cretaceous echinoid, Temnocidaris sceptrifera
65–99 Millions of years

Late Cretaceous
This was a period characterised by the Chalk of Britain. Over 90% of this very pure limestone comprises the skeletons of microscopic single-celled algae. However many other marine organisms are also found, including echinoids, crinoids, ammonites, belemnites, bivalves and gastropods, together with a number of crustaceans and fish (including the coelocanth Macropoma). However, the end of the Cretaceous saw the extinction of the Dinosaurs, ammonites, belemnites, and most of the large marine reptiles.
P549465

An early Cretaceous fern, Cladophlebis, that lived in the Wealden woodlands
99–142 Millions of years

Early Cretaceous
The Wealden woodlands covered southern England at this time. Cycads, conifers and treeferns abound and small ferns, horsetails, clubmosses and liverworts form the undergrowth. Flowering plants began to evolve at this time, although none has been recognised in Britain. It was in this area that most of the dinosaurs of Britain have been recorded. In the north, sediments yield early Cretaceous ammonites, bivalves, ostracods and other marine organisms. By Aptian and Albian times (??? million years ago, the land of southern England had been covered by the sea.
P549559

A late Jurassic ammonite, Rasenia uralensis
142–205 Millions of years

Jurassic
Beginning in the latest Triassic and throughout most of the Jurassic, much of Britain was submerged beneath the sea. Islands formed during the mid-Jurassic in places and plants (including ginkgos) and dinosaur remains are found. The Jurassic is characterised more by its marine animals including the newly evolved ammonites, brachiopods, bivalves, crinoids, fish and marine reptiles. The extinction of the Palaeozoic rugose and tabular corals had taken place at the end of the Permian, and newly evolved scleractinian corals began to proliferate and build reefs.

205 Millions of years

Permo-Triassic
This was a time when most of Britain was land. Britain had moved further north away from the equator where its climate became arid. Although fish, reptilian footprints and plant spores are found in different parts of the rock sequence, compared to the Palaeozoic and Jurassic this was a time of few fossils. Elsewhere mass extinction events saw the disappearance of trilobites, rugose and tabulate corals and many other groups of animal. In Triassic times dinosaurs and mammals evolved.

P549466

A late Carboniferous seed fern, Neuropteris
290–316 Millions of years

Late Carboniferous
Britain was on the equator where the climate was humid. The basins in which the marine animals proliferated in the early Carboniferous were filled by sands and muds as the rivers created massive deltas. The earliest forests grew here with giant clubmosses and horsetails; ferns, tree ferns and seed ferns; and in the drier areas, conifers. It is from this forest that Britain’s coal formed. Large insects and spiders inhabited the forests, amphibians lived on the waterside and the first reptiles had evolved (Westlothiana from East Kirkton, Scotland).

P549523
An early Carboniferous coral, Siphonodendron junceum, from Ecclefechan, Scotland
316–354 Millions of years

Early Carboniferous
Much of southern Britain was covered by a warm tropical sea in which corals, brachiopods, crinoids, gastropods etc. lived with a variety of fish. This was the time when the last of the dendroid graptolites eventually went into extinction.

P550306

A Devonian lungfish, Dipterus, from northern Scotland

354–417 Millions of years

Devonian
Much of Britain was a hot, barren land at this time, although south-western England and parts of Scotland were covered by the sea. Scottish waters were rich in fish including lungfish, whereas goniatites, ostracods, bivalves, brachiopods, corals are found in south-west England. It was during the Devonian that the last of the planktonic graptolites became extinct, although benthic dendroids continued into the early Carboniferous.

P550304
A Silurian crinoid, Periechocrinus from the Welsh Marches
417–443 Millions of years

Silurian
This was a time when much of Britain was covered by the sea (Iapetus Ocean). Scotland was separated from England and Wales, and graptolites and trilobites lived in the deep waters. England and Wales were situated near the equator where shallow warm water contained corals, sponges, trilobites, gastropods, brachiopods and crinoids. In the deeper waters, graptolites, straight nautiloids and trilobites lived. In a few places (e.g. Wales) land emerged through the waves and the earliest vascular plants grew. They were small and lacked leaves.

P549553
An Ordovician graptolite, Didymograptus murchisoni
443–495 Millions of years

Ordovician
This was a time of continued evolutionary radiation. Trilobites reached their peak of diversity, brachiopods were the dominant form amongst the shelly animals, one of the straight types of nautiloids grew to over 4.5 m. long, a giant of its day, and corals began a phase of diversification. Amongst the planktonic species, graptolites were hugely successful and evolved rapidly. Late in the period, spores of non-vascular plants (distant relatives of moss and liverworts) were just beginning to colonise the land.

P550301

Cambrian triliobite, Paradoxides davidis from Wales
495 Millions of years

Cambrian

Rocks of this age occur in Scotland, Wales and a few places in England. They are mainly marine sediments, with animals such as trilobites, brachiopods, gastropods and worms. Biomineralisation resulted in shells and skeletons for the first time

P550159

Late Precambrian Charnia, the earliest multicelled animal known in Britain
545–4600 Millions of years

Late Precambrian
Britain has relatively few Precambrian rocks, but there are river-lain and marine deposits in some places. Although fossil bacteria and rocks known to have formed through the action of bacteria (Banded Ironstone Formations) are known in some parts of the world, there are none known in Britain. However, about 600 million years ago, some of the earliest multi-celled organisms lived in Britain, including soft-bodied sea pens. Burrows are also found.

[[Category:Palaeontology]]

Geological timeline in fossils - Revision history

Dbk: Created page with "By Ian Wilkinson When we speak about geological time, we refer to hundreds or even thousands of millions of years – vast periods of time. To aid in our understanding of th..."