Bynoe Harbour Habitat Mapping Survey 2016: Grain size data for seabed sediments

Bynoe Harbour Habitat Mapping Survey 2016: Grain size data for seabed sediments

Version
1.0.0
Program
Marine
Resource type
Baseline

Background

This resource contains surface sediment data for Bynoe Harbour collected by Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and Department of Land Resource Management (Northern Territory Government) during the period from 2-29 May 2016 on the RV Solander (survey SOL6432/GA4452).

The specific objectives of the survey were to:

  1. Obtain high resolution geophysical (bathymetry) data for outer Darwin Harbour, including Shoal Bay;
  2. Characterise substrates (acoustic backscatter properties, grainsize, sediment chemistry) for outer Darwin Harbour, including Shoal Bay; and
  3. Collect tidal data for the survey area.

Data acquired during the survey included: multibeam sonar bathymetry and acoustic backscatter; physical samples of seabed sediments, underwater photography and video of grab sample locations and oceanographic information including tidal data and sound velocity profiles.


This dataset comprises grain size data measured on seabed sediments.

What this product offers

The intent of this four year (2014-2018) program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions by collating and collecting baseline data that enable the creation of thematic habitat maps that underpin marine resource management decisions.

Related products

Publications

A detailed account of the survey is provided in:

Siwabessy, P.J.W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas W.A., Picard, K., Radke, L.C., Tran, M., Williams, D. and Whiteway, T. 2016. Bynoe Harbour Marine Survey 2016: GA4452/SOL6432 – Post-survey report. Record 2017/04. Geoscience Australia, Canberra.  http://dx.doi.org/10.11636/Record.2017.004.

Data access

Link to data Download the data via eCat
eCat record 104680
CMI RESTful node ID 618
Access constraints

Download data via GeoScience Australia Data and Publications portal eCat.

Security classification Unclassified
Update frequency asNeeded
Product life span -

Accuracy and limitations

Initial processing and determining Mud, Sand and Gravel proportions Sediment samples are first weighed, and then wet sieved over 63 um and 2000 um sieves to determine the percent (%) content of Gravel (> 2 mm diameter), Sand (2-0.063 mm) and Mud (< 0.063 mm). The results are presented as Mud Sand and Gravel percent (%). Gravel and Sand fractions from the wet sieving are put into an oven at 40deg C overnight or longer to dry.

The wet sediment samples, representing a discrete proportion (%) of the bulk sample, from the Mud fraction (< 63 um diameter) are then measured in one of two Malvern Mastersizer particle size analysers for measurement of the fine fraction. Each sample is analysed three times, and the average from these are used as the result for the mud fraction.

Because the Mastersizer particle size data are created in 105 individual size bins, these data are re-assigned to the appropriate size classes used in the Wentworth scale, and the results are presented for the 0-250 um size range. This is because the laser measurement system produces data that is based on spherical particles, yet natural minerals and biogenic particles can have a very non-spherical form.

Repeat analyses of multiple samples of < 63 um sieved sediment at the Pal Sed lab generally results in grain size data for sizes of up to 250 um diameter particles being produced. The laser measurements are undertaken on the volume of particles.

However, because the Mud sample was originally weighed, these data represent the x % by mass of the original bulk sample, determined in the initial stage by wet sieving. Therefore these data can be summed to the outputs of Sand and Gravel % by weight to give baseline grainsize data for the Wentworth scale size bins.

Once the wet sand and gravel fractions are dry, these are then dry-sieved over sieves that match as close as possible the Wentworth scale. Sieve sizes are 63, 125, 250, 500, 1000, 2000 um for the sand fraction, and 2000, 4000, 8000 and 16000 um size for the gravel fraction.

A single analysis is undertaken for the sand, and for the gravel fractions. The results are the proportions by mass as a percent of the sand and of the gravel fractions.

Once the measurements are completed, and Quality Assurance duplicate analyses are undertaken on each of the Mud, Sand and Gravel fractions for approximately 1 in 10 of the samples submitted in each job, the samples are archived dry, and sent to the Repository.

Quality Assurance Approximately 1 in 10 samples in a batch of samples submitted are analysed in duplicate (i.e. replicates). For the Mud fraction, this means that the duplicate sample will also undergo three individual analyses, and the result for the duplicate is the mean of the three analyses. For the coarse fractions, a single sieve analyses is undertaken for the duplicate, the same as for the original.

The full grain-size distribution is produced, and sediment distribution plots are created to compare duplicates (Quality Assurance or QA samples) with the original samples. Outputs of the new grain size method The determination of Mud, Sand and Gravel proportions is the first step in creating a grain size distribution. The proportions of grain size distributions in individual bins originating from Mud, Sand and Gravel proportions are summed to 100 %. For the Mud measurements made using the Mastersizer, this means that the determined size values in the range of 0-250 um is added to the sand fraction because they each are a % proportion of the total.

Once the grain size distribution is determined, the Microsoft Excel-based software Gradistat (Blott and Pye, 2001) is used to calculate the Geometric graphical measures of Mean (MG, Standard deviation (= Sorting, σG), Kurtosis (KG) and Skewness (SkG) originally described by Folk and Ward (1957).

Additionally, to provide summary point information for each sediment sample, the Folk textural classification for coarse sediment (Folk, 1980) is determined for each sample, derived from the percentage proportions of Mud, Sand, and Gravel.

Finally, the Shepard textural classification for fine sediments (Clay, Silt and Sand) is derived for each sample in MARS that has the full grain size distribution. At present, both the Folk and (soon) Shepard textural classes are derived when the final grain size distributions are entered into MARS. This is because these are products derived from data, and are not raw data. Thus the final sign-off of sediment data for release will be after data is entered into MARS.
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References

  • Siwabessy, P.J.W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas W.A., Picard, K., Radke, L.C., Tran, M., Williams, D. and Whiteway, T. 2016. Bynoe Harbour Marine Survey 2016: GA4452/SOL6432 – Post-survey report. Record 2017/04. Geoscience Australia, Canberra.  http://dx.doi.org/10.11636/Record.2017.004.

Lineage

Initial processing and determining Mud, Sand and Gravel proportions Sediment samples are first weighed, and then wet sieved over 63 um and 2000 um sieves to determine the percent (%) content of Gravel (> 2 mm diameter), Sand (2-0.063 mm) and Mud (< 0.063 mm). The results are presented as Mud Sand and Gravel percent (%). Gravel and Sand fractions from the wet sieving are put into an oven at 40deg C overnight or longer to dry.

The wet sediment samples, representing a discrete proportion (%) of the bulk sample, from the Mud fraction (< 63 um diameter) are then measured in one of two Malvern Mastersizer particle size analysers for measurement of the fine fraction. Each sample is analysed three times, and the average from these are used as the result for the mud fraction.

Because the Mastersizer particle size data are created in 105 individual size bins, these data are re-assigned to the appropriate size classes used in the Wentworth scale, and the results are presented for the 0-250 um size range. This is because the laser measurement system produces data that is based on spherical particles, yet natural minerals and biogenic particles can have a very non-spherical form.

Repeat analyses of multiple samples of < 63 um sieved sediment at the Pal Sed lab generally results in grain size data for sizes of up to 250 um diameter particles being produced. The laser measurements are undertaken on the volume of particles.

However, because the Mud sample was originally weighed, these data represent the x % by mass of the original bulk sample, determined in the initial stage by wet sieving. Therefore these data can be summed to the outputs of Sand and Gravel % by weight to give baseline grainsize data for the Wentworth scale size bins.

Once the wet sand and gravel fractions are dry, these are then dry-sieved over sieves that match as close as possible the Wentworth scale. Sieve sizes are 63, 125, 250, 500, 1000, 2000 um for the sand fraction, and 2000, 4000, 8000 and 16000 um size for the gravel fraction.

A single analysis is undertaken for the sand, and for the gravel fractions. The results are the proportions by mass as a percent of the sand and of the gravel fractions.

Once the measurements are completed, and Quality Assurance duplicate analyses are undertaken on each of the Mud, Sand and Gravel fractions for approximately 1 in 10 of the samples submitted in each job, the samples are archived dry, and sent to the Repository.

Quality Assurance Approximately 1 in 10 samples in a batch of samples submitted are analysed in duplicate (i.e. replicates). For the Mud fraction, this means that the duplicate sample will also undergo three individual analyses, and the result for the duplicate is the mean of the three analyses. For the coarse fractions, a single sieve analyses is undertaken for the duplicate, the same as for the original.

The full grain-size distribution is produced, and sediment distribution plots are created to compare duplicates (Quality Assurance or QA samples) with the original samples. Outputs of the new grain size method The determination of Mud, Sand and Gravel proportions is the first step in creating a grain size distribution. The proportions of grain size distributions in individual bins originating from Mud, Sand and Gravel proportions are summed to 100 %. For the Mud measurements made using the Mastersizer, this means that the determined size values in the range of 0-250 um is added to the sand fraction because they each are a % proportion of the total.

Once the grain size distribution is determined, the Microsoft Excel-based software Gradistat (Blott and Pye, 2001) is used to calculate the Geometric graphical measures of Mean (MG, Standard deviation (= Sorting, σG), Kurtosis (KG) and Skewness (SkG) originally described by Folk and Ward (1957).

Additionally, to provide summary point information for each sediment sample, the Folk textural classification for coarse sediment (Folk, 1980) is determined for each sample, derived from the percentage proportions of Mud, Sand, and Gravel.

Finally, the Shepard textural classification for fine sediments (Clay, Silt and Sand) is derived for each sample in MARS that has the full grain size distribution. At present, both the Folk and (soon) Shepard textural classes are derived when the final grain size distributions are entered into MARS. This is because these are products derived from data, and are not raw data. Thus the final sign-off of sediment data for release will be after data is entered into MARS.
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Schema / spatial extent

Bynoe Harbour Habitat Mapping Survey

Update frequency asNeeded
Temporal extent
Coordinate reference system

Owner

Commonwealth of Australia (Geoscience Australia)

License

CC BY Attribution 4.0 International License

Rights statement

© Commonwealth of Australia (Geoscience Australia) 2019. Creative Commons Attribution 4.0 International License.

Acknowledgments

This project was made possible through offset funds provided by INPEX-led Ichthys LNG Project to Northern Territory Government Department of Land Resource Management, and co-investment from Geoscience Australia and Australian Institute of Marine Science.

Thanks to the crew of the RV Solander for help with sample collection, Matt Carey, Craig Wintle and Andrew Hislop from the Observatories and Science Support at Geoscience Australia for technical support and Jodie Smith for reviewing the data.

This dataset is published with the permission of the CEO, Geoscience Australia.