Authors / CoAuthors
Nicholas, W.A.
Abstract
A benthic sediment sampling survey (GA0356) to the nearshore areas of outer Darwin Harbour was undertaken in the period from 03 July to 14 September 2016. Partners involved in the survey included Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Department of Environment and Natural Resources within the Northern Territory Government (NT DENR) (formerly the Department of Land and Resource Management (DLRM)). This survey forms part of a four year (2014-2018) science program aimed at improving knowledge about the marine environments in the regions around Darwin and Bynoe Harbour’s through the collection and collation of baseline data that will enable the creation of thematic habitat maps to underpin marine resource management decisions. This project is being led by the Northern Territory Government and is supported by the INPEX-led Ichthys LNG Project, in collaboration with - and co-investment from GA and AIMS. The program builds upon an NT Government project (2011-2011) which saw the collection of baseline data (multibeam echosounder data, sediment samples and video transects) from inner Darwin Harbour (Siwabessy et al. 2015). Radke, L., Smit, N., Li, J., Nicholas, T., Picard, K. 2017. Outer Darwin Harbour Shallow Water Sediment Survey 2016: GA0356 – Post-survey report. Record 2017/06. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2017.006 This research was funded by the INPEX-led Ichthys LNG Project via the Northern Territory (NT) Government Department of Land Resource Management (DLRM) (now the Department of Environment and Natural Resources (DENR)), and co-investment from Geoscience Australia (GA) and Australian Institute of Marine Science (AIMS). We are grateful to the following agencies for providing boats and staff, and to the following personal for help with sample acquisition: NT DENR (Danny Low Choy and Rachel Groome), NT Fisheries (Wayne Baldwin, Quentin Allsop, Shane Penny, Chris Errily, Sean Fitzpatrick and Mark Grubert), NT Parks and Wildlife (Ray Chatto, Stewart Weorle, and Luke McLaren) and the Larrakia Rangers (Nelson Tinoco, Kyle Lewfat, Alan Mummery and Steven Dawson). Special thanks to the skippers Danny Low Choy, Wayne Baldwin, Stewart Weorle and Luke McLaren whose seamanship strongly guided the execution of this survey. AIMS generously allowed use of the aquarium and laboratory at the Arafura Timor Sea Research Facility, and Simon Harries and Kirsty McAllister helped with the setup. We would also like to acknowledge and thank GA colleagues including: Matt Carey, Ian Atkinson and Craig Wintle (Engineering and Applied Scientific Services) for the organisation of field supplies and the design of the new core incubation set-up. This dataset is published with the permission of the CEO, Geoscience Australia
Product Type
dataset
eCat Id
111901
Contact for the resource
Author
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Digital Object Identifier
Keywords
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- Marine
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- Marine survey
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- Marine baselines
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- Seabed
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- Sedimentology
- Australian and New Zealand Standard Research Classification: Fields of Research
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- Earth Sciences
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- Published_External
Publication Date
2017-08-09T14:00:00
Creation Date
2017-08-09T11:00:00
Security Constraints
Legal Constraints
Status
Purpose
Maintenance Information
notPlanned
Topic Category
geoscientificInformation
Series Information
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 (%). Mud (< 63 um sieved) grain-size measurements 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. Sand and Gravel measurements 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.
Parent Information
Extents
[-12.740464, -12.13859, 130.637289, 131.132551]
Reference System
Spatial Resolution
2-5 m
Service Information
Associations
Source Information