Darwin Harbour Habitat Mapping Program: Sediment grain size data

Brief description

This resource contains sediment grain size data and their summary statistics for the greater Darwin Harbour region. These data were derived from the measurement of sediment grain sizes from seabed samples collected as part of a baseline habitat mapping program for the Darwin Harbour region, including Bynoe Harbour. This project was funded through offset funds provided by INPEX-led Ichthys LNG Project to the Northern Territory Government’s Department of Environment and Natural Resources (NTG-DENR) with co-investment from Geoscience Australia (GA) and the Australian Institute of Marine Science (AIMS). The intent of this 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 and information to underpin marine resource management decisions. The sediment samples were collected during multiple surveys undertaken by GA, AIMS and NTG-DENR between 2011 and 2017. A total of 499 samples are reported on from 489 stations with all grain size data published in the Marine Sediments Database (MARS). This dataset is published with the permission of the CEO, Geoscience Australia.

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Maintenance and Update Frequency: asNeeded

Statement: This dataset is composed of seabed sediment grain size (particle size) and sediment texture data derived from the measurement of grain sizes from sediment collected during multiple surveys including GA0333 (Siwabessy et al., 2015), GA0341 (Siwabessy et al., 2015), GA0351/SOL6187 (Siwabessy et al., 2016), GA4452/SOL6432 (Siwabessy et al., 2017), GA0356 (Radke et al., 2017), and GA0358 and GA0359 (Radke et al., 2018). Sediment grain size was measured at the laboratories of Geoscience Australia from samples collected during the marine surveys for the greater Darwin Harbour region project. Sediment grain sizes were measured using a Malvern Mastersizer laser diffractometer on the < 63 um size fraction (mud) and standard sieve techniques were used to measure the > 63 um fractions (sand and gravel). Because the theoretical basis of both techniques is based around the measurement of spherical particles, the results were combined into a single dataset that covers the size range from fine clay to cobbles, following the sediment grain size classification of Wentworth (1922). Results presented are the complete sediment distributions from 9.5 to -4.5 Φ at 1 Φ intervals, and Mud, Sand and Gravel values, all as percentages. Each Φ value represents the mid-range value for each grain size bin. Statistics calculated and included here are Folk and Ward logarithmic graphical mean and standard deviation (reported as sorting) values (Folk and Ward, 1957). Sediment textures are also presented, and follow the classification of Folk (1974) for coarse grained sediment, and Long (2006) for the EUNIS level 3 sediment texture classes. Both Folk (1974) and Long (2006) classifications are based on the relative proportions of Mud, Sand and Gravel, and the Long (2006) classification is a simplification of Folk (1974). References: Folk, R. L. 1970. Petrology of Sedimentary Rocks. Hemphill Publishing, Austin, Texas. 182 pp. Folk, R. L., Ward, W. C. 1957. Brazos River Bar: a study in the significance of grain size parameters. Journal of Sedimentary Petrology, 27, 3-26. Long, D. 2006. BGS detailed explanation of seabed sediment modified Folk classification. Available from: http://www.emodnet-seabedhabitats.eu/PDF/GMHM3_Detailed_explanation_of_seabed_sediment_classification.pdf Siwabessy, P. J. W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F. J. F., Li, J., Nicholas, W. A., Potter, A., Radke, L. C., Tran, M., Williams, D., Whiteway, T. 2016. Outer Darwin harbour marine survey 2015: GA0351/SOL6187 post-survey report. Geoscience Australia Record 2016/08, 117 pp. 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., Whiteway, T. 2017. Bynoe Harbour marine survey 2016: GA4452/SOL6432 post-survey report. Geoscience Australia Record, 2017/04. 113 pp. Radke, L., Smit, N., Picard, K., Nicholas, T., Li, J. 2017. Outer Darwin Harbour shallow water sediment survey 2016: GA0356 post-survey report. Geoscience Australia Record, 2017/06. 77 pp. Radke, L., Smit, N., Li, J., Hunt-Lew Fatt, K., Low Choy, D., Harries, S, Windsor, J., Nicholas, W. A. 2018. Benthic sediment surveys of inner Darwin harbour and shallow water areas in and around Bynoe Harbour (2017): GA0358 and GA0359 post-survey report. Geoscience Australia Record 2018/52. 135 pp. Wentworth, C. K. 1922. A scale of grade and class terms for clastic sediments. Journal of Geology, 30, 377-392.