Parent record: Datasets relating to core MD002361 (shelf edge offshore Western Australia)

Researchers: Spooner, Michelle (Principal investigator) ,  De Deckker, Patrick (collaborator) ,  De Deckker, Patrick, Prof (collaborator)

Brief description We must understand the natural cycles of the oceans to understand the evolution of our climate through geological time. Core MD 002361 was obtained in 2000 off the coast of Sumatra (113.477166 E, 22.082 S). By investigating the properties and components of this core we are able to reveal some information regarding past oceanographic and climatic systems. Information obtained or inferred from the core include the isotopic composition of oxygen and carbon through time, an age vs. depth profile of the core (revealing sedimentation rates), the relative abundance of planktonic foraminifera over time, and estimates of historical sea-surface temperatures. The core description highlights the stark contrast between glacial and interglacial periods with 1-1.5m bands of red clay indicating interglacial periods, alternating with the 1-1.5m bands of light grey foraminifera sand deposited during the glacial periods.

Lineage Maintenance and Update Frequency: notPlanned

Lineage Statement: Sample collected using a piston core. For isotope analysis carbonate tests of Gs. ruber were prepared, cleaned and then collected using 63mm mesh. Calculations of 13C and 18O at various depth were made by the Finnegan MAT 251 Mass Spectrometer at the Research School of Earth Sciences, ANU. The age-model for the core was determined through radiocarbon dating in the upper sections (down to 204cm) and then followed the chronology of Bassinot et al. as the core extends beyond the Marine Isotope Stages (MIS) of SPECMAP. Relative abundances of planktonic foraminifera were based on counts of splits of the >150mm fractions to remove juvenile and possibly unidentifiable fragments. Each sample was split by an Otto-micro splitter until about 400 species were present in the final split. Sea-surface temperatures (SST) were estimated from planktonic foraminifera assemblage data using the modern analogue technique (MAT), in conjunction with the AUSMAT-F4 database. Each SST estimate was calculated as the mean of the best 10 analogues from the global database.

Lineage Statement: The Mass spectrometer was run concurrently with international standards NBS-19 and NBS-18, and has a very small analytical error. None of the isotope values have been amended to account for the ice-volume effect on the foraminifera during the Last Glacial Maximum (LGM). Data was sampled every 4cm down the core to a depth of 295.5cm, at which point sampling was conducted every 5cm. This sampling continued down the core to 1360cm. There is some missing data for both 18O and 13C mainly around the 900-1100cm depth. For this region of the core, values for 18O and 13C have generally been calculated every 10cm. Radiocarbon dating was used to construct an age-model for the upper sections of the core. Radiocarbon ages were obtained from 12 samples down to a depth of 204.5cm. The age model used for the rest of the core is based on the chronology of Bassinot et al. as the core extends beyond the MIS of SPECMAP. This study captures isotopic events in the tropical Indian Ocean and is accurately tuned to the astronomical time scale. In relation to relative abundance of foraminifera, individuals were accurately identified to the species level. Sea-surface temperatures (SST) were estimated from planktonic foraminifera assemblage data. The most precise variable of SST is mean annual temperature, followed by Tmax, then Tmin. Most of the SST estimates are reasonably precise given that the samples have good analogues in the AUSMAT-F4 database. Stages with reduced quality of SST estimates are during MIS 5 (70k-130k yrs BP) and MIS 7 (180k-240k BP). Isotopic composition - parameters: Core depth (cm), oxygen-18 Gs.ruber (parts per thousand), carbon-13 Gs.ruber (parts per thousand). Age vs. depth - parameters: Core depth (cm), age (yrs BP). Relative abundance - parameters: Age of core (yrs BP), relative abundance of planktonic foraminifera assemblages (%). Estimated ocean temperatures - parameters: Age of core (yrs BP), mean water temperature (oC), maximum water temperature (oC), minimum water temperature (oC), depth of mixed layer (m), temperature at 50m, 100m and 150m (oC). Core description - parameters: Depth of core (cm), isotope stages, written description of core material at various depths.

Notes Credit
The Australian National University (ANU)

Notes Credit
Funded by The National Oceans Office (NOO)

Notes Credit
Funded by The Australian Research Council (ARC)

Notes Credit
Funded by The Australian Institute of Nuclear Science Engineering (AINSE)

Notes Credit
Funded by The French Polar Institute

Notes Credit
Funded by The Murray Darling Basin Commission

Notes Purpose
To provide an insight into palaeoceanographic conditions on the shelf-edge off Western Australia. Also, to define the history and behaviour of the Leeuwin Current, determine past ecological conditions in the water column and to gain insight into the interactions within the water column.

Data time period: 2000-01-01 to 2000-01-01

113.48338,-22.09163 113.48516,-22.09177 113.48469,-22.09283 113.4836,-22.0927 113.48338,-22.09163

113.48427,-22.09223

113.5,-22 113.5,-22.5 113,-22.5 113,-22 113.5,-22

113.25,-22.25

text: westlimit=113; southlimit=-22.5; eastlimit=113.5; northlimit=-22

text: uplimit=1805; downlimit=1805