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Sedimentology and holocene history of a tropical estuary (Broad Sound, Queensland)

Broad Sound is situated at the confluence of four large estuaries. Freshwater inflow is restricted to the summer months. The Sound and its attendant estuaries are characterized by shallow water, a large tidal range (10 m), and strong tidal currents. In the shallow marine environment (the most seaward) pre- Holocene relict calcareous gravels are common. Calcareous sands, commonly occurring as sand ridges capped by megaripples, predominate in the open intertidal environment. Muds are most abundant in the mangrove swamp, mangrove channel, and supratidal flat environments, the muds become less calcareous and more saline in a landward direction. Textural studies revealed that grainsize parameters can be used to divide the sediments into environmentally significant groups; they also indicated that most of the sediments are brought into the estuaries during times of summer floods, and redistributed by tidal currents during the remainder of the year. The petrology and mineralogy of the sediments are consistent with some relative seaward movement of terrigenous sediment and landward movement of calcareous sediment. The relict nature of some of the sediments is revealed by their mineralogy, in particular their lack of less stable carbonates and heavy minerals. There is a seaward trend of increasing maturity in both the heavy-mineral and light-mineral assemblages. Drilling and radiocarbon dating have shown that most of the sediments are of late Holocene age. It appears from the Broad Sound evidence that sea level stabilized about 6000 years ago. Since that time there has been a marked seaward progradation of the shoreline producing a 'fining upward' regressive sequence. Regression appears to have been more rapid on the east side of the Sound, possibly a result of some late Holocene uplift. The Broad Sound study is valuable because it provides not only a regressive model for environmental interpretation in ancient sediments, but also a yardstick against which environmental changes in tropical estuaries can be measured.

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Data and Resources

Additional Info

Field Value
Title Sedimentology and holocene history of a tropical estuary (Broad Sound, Queensland)
Type Dataset
Language English
Licence Creative Commons Attribution 4.0 International
Data Status inactive
Update Frequency asNeeded
Landing Page http://data.gov.au/dataset/f3171ec9-72c3-42b1-b330-063fc0cc7a96
Date Published 2017-03-17
Date Updated 2017-03-17
Contact Point
Geoscience Australia
Geospatial Coverage {"type": "Polygon", "coordinates": [[[149.5, -23.0], [150.0, -23.0], [150.0, -22.0], [149.5, -22.0], [149.5, -23.0]]]}
Jurisdiction Commonwealth of Australia
Data Portal Australian Oceans Data Network CSW Harvester
Publisher/Agency Geoscience Australia
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