Citation

Mathews, E.J., Heap, A.D. & Woods, M., 2007. Inter-reefal seabed sediments and geomorphology of the Great Barrier Reef, a spatial analysis. 1 ed. Record  2007/009. Geoscience Australia, Canberra.

Abstract

Inter-reefal (i.e. non-reefal) seabed environments have been much less studied than the coral reefs, however they comprise 95% of the total Great Barrier Reef (GBR) Marine Park area. Regional scale spatial analysis of the sediments and geomorphology in these areas allows for a systematic characterisation of the seabed, where comprehensive biological datasets are lacking. We offer an up-to-date synthesis of inter-reefal environments in the GBR, to better understand the nature and distribution of seabed habitats at a regional scale and within the current planning zone scheme, in support of Marine Park management. New quantitative information about surface sediments and geomorphic features, together comprise a new physical dataset of the GBR seabed. This regional dataset contains over 3,000 sediment samples available in Geoscience Australia's (GA) national marine samples database, MARS (www.ga.gov.au/oracle/mars), substantially improving the coverage of surface sediment data from inter-reefal areas, and; GA's current Geomorphic Features dataset (Harris et al., 2005) of the seabed morphology. This marks the first regional synthesis of the surface sedimentology and geomorphology of the GBR since the pioneering work of Belperio (1983a, 1983b) and Maxwell (1968; 1969a; 1969b; 1973). We present a new quantitative sediment dataset that shows regional trends in surface sediments; refining the existing facies model for the mixed carbonate-siliciclastic GBR margin. Our findings also reveal local scale facies characteristics, within the broader regional trends. Until now these distribution patterns haven't been identified on the GBR shelf and are considered to be an important characteristic of the region. In addition, we have revealed other sedimentary characteristics of the region; - Low gravel concentrations cover extensive parts of the shelf. Patches of high gravel concentration occur locally on parts of the inner and outer shelves, reflecting the input of gravel from reef talus aprons. These areas may also be associated with strong tidal currents. - Sand is the dominant grain size fraction, and highest concentrations occur on the middle and outer shelves. Although continuous regions of high sand concentration occur in the far north (e.g. Cape York) and south (e.g. south of Broad Sound) of the Marine Park, the overall distribution of sand is variable as changes in concentration produce local, small-dimension patches at a scale of 10's of metres. - The patchy distribution of sand may reflect a mixture of; 1) widespread supply of modern skeletal carbonate grains, such as foraminifera, molluscs and Halimeda, and/or restricted supply of relict sand; and, 2) the effects of hydrodynamic irregularities in inter-reef channels. - High mud concentrations predominantly occur along the inner shelf and slope. Mud forms local patches on the inner shelf associated with fluvial point sources, which are spatially discontinuous, producing a regionally variable terrigenous sediment wedge of coalescing mud (and sand) patches. - Surface sediments are carbonate-dominated across the shelf and broadly display a regional north-south, shelf-parallel zonation pattern. Low carbonate concentrations of <40% on the inner shelf denote high terrigenous compositions, which increase to >80% on the outer shelf. Within the regional zonation pattern, carbonate patches locally produce a variable distribution in sediment composition. - Uniformly high concentrations of bulk carbonate and carbonate mud on the outer shelf, reflect the constant supply of skeletal carbonate grains from inter-reefal environments, in areas of high reef density and the negligible influence of fluvial sediments on the outer shelf. Regional variations in seabed sediments and geomorphology across the region are also evident in the physical character of the planning zones.
Google map showing geographic bounding box with values North bound -10.0 East bound 154.0 West bound 142.0 South bound -30.0
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Product Type/Sub Type

dataset - GA Publication - Record

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2007

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Record
marine
mapping
marine park
seabed
continental shelf
sedimentology
habitat
marine zone
geomorphology
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-10.0
East bound
154.0
West bound
142.0
South bound
-30.0

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-d086-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2006-06-01

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
Related Links
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays