Graduate Thesis Proposal

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Graduate Thesis Proposal
The paleoecology of Pennsylvanian
extrabasinal floras

• Arden R. Bashforth
• ERTH6300

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The Carboniferous World
R.C. Blakey http//jan.ucc.nau.edu/rcb7/300_Penn
_2globes.jpg
very different from our own!
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Defining floral habitats and main objective of
the project

• Basinal lowlands - paleovalley floors, rivers,
  lakes, peat swamps
• Extrabasinal lowlands - sides of paleovalleys,
  100-200 m elevation
• Extrabasinal uplands - outside confines of basin

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Why study extrabasinal plants?Soil formation,
sedimentation, erosion

• After Algeo et al. (1995)

• Roots caused increased soil production and
  sediment supply
• Baffled sediment, reduced erosion, stabilized
  landscape

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Why study extrabasinal plants?Paleoatmospheric
compositions

• After Algeo et al. (1995), Berner (2003)

• Increased O2 due to photosynthesis
• Decreased CO2 due to silicate weathering, organic
  carbon sinks
• Global cooling and glaciation
• Estimates do not account for extrabasinal plants

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Why study extrabasinal plants?Glaciation and
floral turnovers

• After Gastaldo et al. (1996), Cleal and Thomas
  (2005)

• Correlation between glacial maxima and extent of
  peat-forming forests
• Deglaciation triggered warming and drying trends
• Demise of most peat-forming forests and floral
  turnovers

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Which rocks preserve extrabasinal
floras?Maximum flooding deposits

• Basinal lowland plants flourishing
• Pollen from extrabasinal habitats subdued

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Which rocks preserve extrabasinal
floras?Maximum flooding deposits

• Deglaciation causes marine incursion, basinal
  lowland habitat flooded

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Which rocks preserve extrabasinal
floras?Maximum flooding deposits

• Basinal lowland plants drowned
• Pollen from extrabasinal habitats amplified

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Which rocks preserve extrabasinal
floras?Basin-margin strata

• Alluvial fan, debris flow, proximal fluvial
  deposits
• Paleosols with plants in growth position in
  exceptional circumstances

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Which rocks preserve extrabasinal
floras?Incised paleovalleys

• Paleovalleys in extrabasinal settings distant
  from basinal lowlands
• Contain flora unique from lowland settings

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What did extrabasinal plants look like?
Gigantic cordaitaleans (50 m tall, 2 m
diameter) Falcon-Lang and Bashforth (2005)
Medullosan pteridosperms Bashforth (2005)
Noeggerathialeans Simunek and Bek (2003)
Conifers (Walchia)
Callipteris
Taeniopteris
Cridland and Morris (1963)
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Main study areas

• After Oplustil (2004)

• Paralic basins with occasional marine incursions
• Limnic basins entirely terrestrial sedimentation

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Objectives

• (O1) Analyze composition, extent, and
  paleoecology of extrabasinal floras
• (O2) Compare with basinal lowland floras
• (O3) Evaluate hypothesis of upland evolution
• (O4) Correlate changes in plant communities and
  depositional systems
• (O5) Determine variables responsible for floral
  turnovers

O1
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Objectives

• (O1) Analyze composition, extent, and
  paleoecology of extrabasinal floras
• (O2) Compare with basinal lowland floras
• (O3) Evaluate hypothesis of upland evolution
• (O4) Correlate changes in plant communities and
  depositional systems
• (O5) Determine variables responsible for floral
  turnovers

O2
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Objectives

• (O1) Analyze composition, extent, and
  paleoecology of extrabasinal floras
• (O2) Compare with basinal lowland floras
• (O3) Evaluate hypothesis of upland evolution
• (O4) Correlate changes in plant communities and
  depositional systems
• (O5) Determine variables responsible for floral
  turnovers

O3
site of evolution(?)
downslope movement after drainage(?)
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Objectives

• (O1) Analyze composition, extent, and
  paleoecology of extrabasinal floras
• (O2) Compare with basinal lowland floras
• (O3) Evaluate hypothesis of upland evolution
• (O4) Correlate changes in plant communities and
  depositional systems
• (O5) Determine variables responsible for floral
  turnovers

plant response to changes in sediment
supply/ substrate conditions/water table
O4
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Objectives

• (O1) Analyze composition, extent, and
  paleoecology of extrabasinal floras
• (O2) Compare with basinal lowland floras
• (O3) Evaluate hypothesis of upland evolution
• (O4) Correlate changes in plant communities and
  depositional systems
• (O5) Determine variables responsible for floral
  turnovers

floral turnovers
geologic/paleoclimatic variables(?)
O5
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Facies AnalysisFieldwork and Boreholes
Mirosov Horizon Czech Republic
Alluvial fan conglomerate

• Alluvial fan, debris flow, proximal fluvial,
  paleovalley deposits
• What sedimentary facies contain extrabasinal
  plant fossils?
• Reconstruction of depositional environments and
  plant habitats
• Temporal and lateral changes in depositional
  environments?
• Associated changes in plants?

Fossiliferous siltstone
Alluvial fan arkose
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Qualitative AnalysesTaphonomy

• Transported assemblages
• type and quality of preservation
• fragmentation
• paleocurrent orientations
• associated sedimentary structures
• Plants rooted in growth position
• extent of root penetration
• soil formation (paleosols)
• spacing

Blanche Brook formation, NL
Joggins Formation, NS
Falcon-Lang (2005)

• Indications of composition and community density
• Effect of plants on soil production, rates of
  erosion and sedimentation

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Quantitative AnalysesPoint Quadrat Technique
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Quantitative AnalysesReconstructing Original
Community Dynamics

• Percent Cover and Percent Flora
• biomass estimation

• Calculation of paleoecological dynamics of
  original plant communities
• Species Richness
• Diversity
• Evenness

• Correlate between community dynamics and
  depositional environments
• Indication of plant responses to changes in
  sedimentation, substrate, water table
• Evidence for geologic and paleoclimatic variables
  causing floral turnovers

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Palynology and Macroflora Taxonomy

• Spores and pollen
• very durable
• record plants not preserved as macroflora
• provides quantitative check on paleoecological
  values
• Consistent taxonomic nomenclature
• A assigned to Neuropteris ovata
• by Zodrow and McCandlish (1980)
• B assigned to Neuropteris plicata
• by Sternberg (1825)
• Compare timing of first appearances in
  extrabasinal and basinal lowland floras
• composition of floral turnovers
• did plants evolve in extrabasinal settings?

B
A
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Significance and Conclusions

• Effects of extrabasinal plants on landscape
  evolution
• Response of plants to changes in sedimentation
  and water table levels
• What geologic and paleoclimatic factors caused
  floral turnovers?
• Did plants actually evolve in upland settings?
• More accurate estimation of global carbon cycle
• and paleoatmospheric compositions