Parent record: Datasets relating to core GC-14, located in the Capricorn Channel at a depth of 2004 mbsl

Researchers: Bostock, Helen (principalInvestigator) ,  Bostock, Helen, Dr (principalInvestigator) ,  Opdyke, Bradley, Dr (collaborator)

Brief description Core GC14 (23o49' 52S 154o21' 67E) was collected from the Capricorn Channel at a depth of 2004 mbsl (metres below sea level). By investigating the properties and components of this core we are able to reveal some information about this hemi-pelagic sedimentary environment over the last glacial / interglacial cycle. Information obtained or inferred from the core include the isotopic composition of oxygen and carbon through time, an age vs. depth profile and the percentage of grainsize fractions throughout the core. X-ray Diffraction (XRD) analyses were also run on several samples from each core to determine changes in the carbonate mineralogy and terrestrial influx, which provided further palaeoclimatic information.

Lineage Maintenance and Update Frequency: notPlanned

Lineage Statement: STABLE ISOTOPES AND GRAINSIZE - Samples of foraminifera were dried in the oven at 60oC before re-soaking in distilled water. Samples were wet sieved through a series of 4 mesh sizes (400µm, 300µm, 200µm and 100µm) before the size fractions were transferred to drying trays. After drying the size fractions were weighed to determine the % of each grainsize from the overall collected dry sample. 10-15 large foraminifera (>300 µm and >400µm) were then hand-picked picked under microscope before being washed in methanol and ultrasonicated for 30 secs to remove any surface and internal particles. Samples were analysed at the Research School of Earth Science, Australian National University, using an automated individual carbonate reaction (Kiel) device coupled with a Finnigan MAT-251 mass spectrometer. XRD - Samples were ground in an agate mortar with acetone or ethanol, then dried, and filled into side-packed sample holders. Powder diffraction data was collected at room temp with a Siemens D501 diffractometer at the Department of Earth and Marine Science, Australian National University. The diffractometer was equipped with a curved graphite monochromator, a scintillation detector, and CuK alpha radiation was used. Scans recorded in one pass from 2 to 70 degrees 2-theta, using a step-width of 0.02 degrees and a scan speed of 1 degree per minute. Results Interpreted using the SIEMENS software package Diffracplus Eva (2000), and quantitative estimates performed using Siroquant 2.5.

Lineage Statement: STABLE ISOTOPES/AGE MODEL & GRAINSIZE - Values are provided for 1cm, 5cm, 10cm, 15cm, 20cm and then every 10cm down the core to depth of 260cm. Mass spectrometer was run concurrently with international standards NBS-19 and NBS-18, and has a very small analytical error.The percentage values for grainsize at each sample depth is not accurate. This is due to wastage during washing and sieving and occasional spills. The age-model was constructed by correlating 18-O values with the SPECMAP age-model. Values of 18-O have a very small analytical error. XRD - XRD analysis was undertaken for two samples within core GC14. The first, at the sediment surface represents interglacial sediment, while the second sample at 80cm, represents glacial sediments. Clay data must be treated with caution since it has been suggested that clay minerals, transported to the coast by river suspended loads, undergo significant diagenesis within environments like mangroves. The percentages of sample components are not exact and the dataset also displays the % error of each component. Errors range from 0.06 - 0.76%. Stable isotope parameters: Depth in core (cm), oxygen-18 G. ruber (parts per thousand), carbon-13 G. ruber (parts per thousand). Age-model parameters: Depth through core (cm), age model (yr BP), sedimentation rate (cm/kyr). Grainsize parameters: Depth through core (cm), grainsize (µm), percentage of total dry mass at each sample depth (%). XRD parameters: XRD run number, sample code and depth (cm), percentage of sample components (%), total percentage (%).

Notes Credit
Funded by The Australian Research Council (ARC)

Notes Credit
Funded by The Australian National University (ANU) Faculties Research Grant Scheme

Notes Purpose
The data from the stable isotopes of Globigerinoides ruber, grainsize, and x-ray diffraction of samples for their mineralogy, allows a preliminary understanding of this hemipelagic sedimentary environment over the last glacial / interglacial cycle. Very little work has been previously undertaken within this area.

Data time period: 1997 to 1997

154.36078,-23.82506 154.36161,-23.82507 154.36141,-23.82566 154.36083,-23.8256 154.36078,-23.82506

154.361195,-23.82536

154.5,-23.5 154.5,-24 154,-24 154,-23.5 154.5,-23.5

154.25,-23.75

text: westlimit=154; southlimit=-24; eastlimit=154.5; northlimit=-23.5

text: uplimit=2004; downlimit=2004