Determining main carbonate mineralogy, and the primary components of the non carbonate fraction, at four depths in core GC12, collected from the Capricorn Channel.
Updated: 2015-05-07
A gravity core (GC12) was collected from a depth of 990.5 mbsl within the Capricorn Channel, southern Great Barrier Reef (GBR). Analysis of other parameters revealed the Last Glacial Maximum (LGM) sitting at a depth of ~175cm into the core. Four samples were collected for X-ray Diffraction (XRD) analysis; the top two, at the sediment surface (GC12-0) and at 30cm (GC12-30) represent interglacial sediment, while the lower two, at 210cm (GC12-210) and 330cm (GC12-330) represent glacial sediment. XRD analysis suggests that the majority of the carbonate is calcite during the interglacials, primarily from pelagic carbonate production. During the glacials and transitions more quartz, feldspar, aragonite and Mg calcite are present. This suggests that there is a changing dominance of pelagic, terrigenous and reef platform material within the core related to sea-level variations.
Data
- ANU_Bostock_GC12_5_data.xls
- aodn: bluenet_datasets_capricorn_channel
- Full metadata link
- http://i.creativecommons.org/l/by/2.5/au/88x31.png
- http://creativecommons.org/licenses/by/2.5/au/
- {"title":"Parent record: Datasets relating to core GC-12, located in the Capricorn Channel at a depth of 990.5 mbsl","recordAbstract":"Core GC12 (23o34' 37S 153o49' 94E) was collected from the Capricorn Channel at a depth of 990.5 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, the percentage of grainsize fractions throughout the core and the percentage of carbonate material in each sample. 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."}
- {"title":"Determining the grainsize of sediment with increasing depth in core GC12, located in the Capricorn Channel","recordAbstract":"A gravity core (GC12) was collected from a depth of 990.5 mbsl within the Capricorn Channel, southern Great Barrier Reef (GBR). Samples were separated into different size fractions to determine the % of each grainsize at each sample depth. Although not overly accurate, the information is correlated with analyses of other parameters to impart clues to the environmental changes within the core. The smallest size fraction (<100µm) dominates at all depths, with an average of 95% in this size bracket at the base of the core. A peak in the larger grainsize fraction at 490cm is the result of a pteropod layer within the sediments. These pteropod accumulations are regular features within the cores. The exact reason for their occurence is unknown."}
- {"title":"Oxygen isotope (18-O) values for 5 different foraminiferal species down the core of GC12, collected from the Capricorn Channel","recordAbstract":"A gravity core (GC12) was collected from a depth of 990.5 mbsl within the Capricorn Channel, southern Great Barrier Reef (GBR). The 18-O values of the different foraminiferal species down the depth of the core show relatively consistent inter-species offsets throughout the glacial and interglacial periods. This provides us with confidence that the 5 individual species presumably remained within the same water mass. Because each foraminifera species fractionate carbon and oxygen isotopes differently, amended 18-O values are given whenever possible to account for these well-known biological vital effects. Comparison of the 18-O values with SPECMAP (Martinson et al., 1987) provides us with a chronology for core GC12."}
- {"title":"Carbon isotope (13-C) values for 5 different foraminiferal species down the core of GC12, collected from the Capricorn Channel","recordAbstract":"A gravity core (GC12) was collected from a depth of 990.5 mbsl within the Capricorn Channel, southern Great Barrier Reef (GBR). 13-C values were recorded for 5 foraminiferal species through the core, with results varying considerably throughout the last 30kyr. The 13-C values of the benthic Cibicidoides spp. are the lowest, whilst those for the planktonic species are comparable, once correlated for their vital effects (except Globorotalia truncatulinoides because no correction for vital effects is available). It is apparent from the 13-C values that there are 3 main 13-C phases during the glacial/interglacial transition: Glacial, Deglaciation and Holocene phases."}
