Lecture 11: The Carboniferous Massive: the great coal swamps. Flashcards
Devonian saw…
plants develop from low herbs to woody trees
Archaeopteris
~10m high: first forests
when did woody trees die out?
At Devonian/ Carboniferous boundary
Forests did not re-establish until
Mid Carboniferous
In late Devonian, landmasses were…
southerly, arid
By Carboniferous the landmasses had moved towards
the Equator & had become tropical and humid
vast thicknesses of warm water limestones (e.g. Carboniferous Limestones of Peak District, Cheddar Gorge, etc.)
Plants were causing…
the climate to change…
Vast lowland coastal areas became
vegetated
plants (+ lignin + charcoal) were locking up
CO2atm as Corg
By mid Carboniferous
what plummeted?
what soared?
CO2atm plummeted, and O2atm soared
glaciation: Sn. polar ice cap
Carboniferous =
“Coal bearing”
Sea-level dropped and so exposed more…
lowland areas for plants to colonise
plant material became preserved in the rock record as coal
‘Coal Measures’ have been exploited for ~400 yrs
‘swamp’ =
lowland containing woody plants, fed by groundwater (e.g., rivers)
Coal can’t be produced in delta-top swamps as…
Too little organic carbon (‘peat’) can build up to produce the thickness of coal seen in the Carboniferous
Rivers switch channels laterally: cover swamps with sediment before enough peat can build up
Rajang Delta in Sarawak (Borneo)
Huge thicknesses of organic matter build up in raised mires, built up above the land/water table level
Wet conditions due to rainfall, not river supply (‘ombrotrophic – rain-fed - mires’)
More peat built up during Carboniferous glacial phases (than in interglacials)
Rivers incised and sediment load bypasses mires
Plants produce many different organs throughout their lifespans
Organs separate during life and death
Each organ can be found as
An individual fossil
Fossil organs from an individual plant have different generic names
One plant is represented by several “form genera”
Carboniferous, erroneously called the “Age of Ferns”
actually relatively low fern diversity in Carboniferous
ferns: pteridophytes
reproduce using spores
still homosporous
More like the “Age of Seed-ferns”
pteridosperms or seed-ferns
fern-like foliage
no wood: held up by interwoven roots & leaf bases
Alethopteris / Neuropteris
maximum 10 m in height
Spore-producing plants
modern horsetails <4 m high
in Carboniferous reached arborescent (tree-like) size: up to 20 m (60 ft) tall…
Carboniferous ‘trees’ often found preserved where they grew
e.g., Fossil Grove, Glasgow
10 trunk/root systems, rotted in life position & filled with sand
lycopods
Giant club mosses: ‘scale trees’
Arborescent lycopod Lepidodendron
Thick bark covered in ‘leaf’ scars root: Stigmaria ‘leaf’ scale: Lepidophyllum reproductive cone: Lepidostrobus up to 54 m (180 ft) high
Going hetero…
reproductive organs in a cone
Produced separate male and female reproductive structures ♀ megaspores at bottom ♂ microspores at top heterospory could cross- and self-fertilise
A new form of plant sex
no. of megaspores reduce, not shed, retained on plant
♂ spores become modified into ♂ pollen
pollen fertilizes megaspore, produces a seed (<10 cm in size)
fleshy outside: food source
animals eat, excrete, disperse seeds
Sea ‘scorpions’
some probably amphibious
freshwater by late Carboniferous
no evidence for venom, but predatory
The Giant Claws
Silurian: Mixopterus
40 cm, freshwater aquatic and terrestrial
Silurian: Pterygotus - 2.3 m
Devonian: Jaekelopterus – 2.5 m long
Massive myriapods
palaeodictyoptera: extinct insects bold colour patterns up to 55cm wingspan piercing, sucking mouthparts were complex structures on new seeds to guard the ovule against insects?
Giant dragonflies: Meganeura
Patterned wings, 75 cm wingspan
Today a short lived part of the life cycle
‘Roaches…
cockroaches
little changed since Carboniferous
but rather larger in size at 9cm!
