L7- Case Study: Carboniferous Coal Measure Forests

• forests are dense, don’t have many tetrapods but there are fish and aquatic arthropods in the rivers, lakes and swamps (secondarily aquatic tetrapods)

• gondwana and euramerica collide, uplift the equatorial basins from west to east, dorests start to dry out due to amount of coal deposited

  • lycopsids/ferns/spehnopsids/pteridosperms→

  • tree ferns/pteridosperms/cordaites→

  • pteridosperms/cordaites/conifers→

  • desert

• forests persist in China into the Permian

Evidence for forests:

Geology:

• sediment is continually deposited→ have rocks forming for all periods of time

• geologists map rocks

• palaeontologists look at the environment and fossils→ reconstruct the environment and biota

• UK→

  

  • mountain front is starting in the south, behind is a basin- wet are where coal measure forests are, north is high, rocks eroded from top and bottom, coal formed by forests, fossils building up

• quarry face→

  

  • mudstones, sands, thick coal, tree trunk, sand, thick coal

  • interpret→ most of the thickness is the sediment but 10m of peat = 1m coal

  • peat accumulate in floods in 5 years

  • coal accumulates in 7000 years

  • coal builds up forest, every now and then get a flood, destroys forest, forest grows again→ allows tree trunk to be preserved upright

  • most of the time is the coals

• look at cyclothems→ relates to interglacial (warmer) and glacial (colder) periods, related different formations to cycles

  

Plant fossil record:

• different parts of plants have different names→ bring together in whole plant reconstruction

  

• taphonomy→ understanding the process to being fossilised, are many ways:

  

• how was the plant fossilised?

  

  • coalified compression→buried in sediment, flattened, film of carbon is left

  • sediment fills the gap that has rotted awat

  • buried, minerals are depositied in the cells (premineralisation)→ exceptional preservation

  • most plants are coalified or moulds/casts

  • exceptional preservation→

    • premineralisation (important→ plants with premineralisatiom→ anatomically preserved plants)

    • coal balls→ peat lays down, coal balls form, are compressed, preserves everything in the coal

    • charcoalification→ regular forest fires, 3D preservation

• 2 fossil records:

  • plant megafossils

  • plant dispersed microfossils→ dissolve rocks up, get lots of pollen/spores, study on microscopes

    • each plant has a unique pollen type→ can link pollen location to sporangia

    • need to mention this as every project has someone dissolving up the rock and finding this

Analysis of rocks/fossils:

• quarry face:

  • get fossils for each rock type→ know what fossils are there? how did they get there?

Coal Measures:

• get different vegetations for different areas:

  

• coal balls→ show lycopsid pollen

• levy river→ bursts its bank, kills the forest, find different flora of plants living in the levy

• marine incursion→ interglacial sea level rises, find conifer pollen blown in from the forest and charcoalified pollen

• find different fossils, different fossils→ can see environmental change and co-existing biotas in different parts of the forest

• sea level changes→ base level changes