geoscience australia australian government geoscience australia applications of geomorphic mapping...
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Geoscience Australia
Australian Government
Geoscience Australia
Applications of geomorphic mapping
and physical data to bioregionalisation
Alix Post & Phil O’Brien
Geoscience Australia
www.ga.gov.au
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Macro-zoobenthos core communitiesGutt (2007)
• Sessile suspension feeder community• Infauna and mobile deposit feeder
community
Primary controls – Phytodetritus flux and sea bed “hardness”
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Creating geomorphic map
Input data• GEBCO contours• ETOPO2 satellite bathymetry grid• Seismic lines
Output• Polygons hand digitised
in ArcGIS• 28 categories of geomorphic
features recognised
N
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Prydz Bay
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Prydz Bay
Shelf depression:< 550 m with closed contours. Typically muddy, biogenic sediments.
Shelf bank:Typically 100-200 m, extending to 500 m. Ice scoured.
Cross shelf valleys:Shelf depression <500 m connected to shelf edge. May be current swept.
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Prydz Bay
Upper slope:Mapped from max gradient to lower gradient at ~2500 m. Highly gullied and current swept.
Trough mouth fan:Sediment apron on upper slope.
Lower slope:Extends to lower limit of canyons. Comprises alt. canyons and ridges.
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Prydz Bay – Sediments &geomorphology
Phytodetritus-richooze distributioncontrolled by geomorphology
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Seamount on seismic line
Height above seabed > 1000 m
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Marginal ridge – Outer Adélie Rift BlockMarginal ridge – Outer Adélie Rift Block
D1601Granite, gneiss,
diorite, pelite
7
6
5
S N10 km
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George V-Terra Adélie margin – Geomorphic Units
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Biogeomorphicunits George V shelfBeaman & Harris,(2005)
Data:MultibeamSingle beamGrab samplesCoresPhotosCTDs
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Mertz Drift
Presti et al., Quaternary Science Reviews, 2005
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Spearman rank correlation = 0.71
Muddy
Deep/flat
Rocky substrate
Relief
Scours
Coarsesubstrate
Shrimp,infaunal holothurians
Sponges & bryozoa
Bryozoa, sponges, colonial
tunicates
PCA of taxa with correlation to substrate
Bryozoa, sponges, soft
corals
Sponges & solitary tunicates
Post et al., DSR II in press
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Hydrocorals and canyon heads, George V continental slope(Post et al., Ant. Sci, 2010)
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Conclusions
• Shelf geomorphic units approximate Community-level habitats
• Public bathymetry data sets useful for bioregionalsiation on the scale of around 1: 1 million
Should have value for the slope, rise and deep ocean