Sedimentary Records And Paleoclimate Evolution Of The Great Barrier Reef, Australia During The Past150000Years

The issues of climate change and its influence on human and environment are ofimportance to human survival and development. Investigating the dynamicmechanisms for paleoclimatic change is useful for predicting future climate change.Reconstructing the history of sea surface and climate variations during the lastinterglacial/glacial in the low-altitude ocean of southern hemisphere is of greatsignificance to the understanding of Antarctic Ice Cover melting and its relatedclimate-environment changes. However, such studies are limited. So this study was tostudy the mineralogy and geochemistry of the sediments of the cores from IntegratedOcean Drilling Program (IODP)325expedition. An integrated approach wsaemployed including X-ray diffraction, geochemistry, and redness analyses.The resulting data was comparable with that from the Vostok ice core (Antarctic).The results showed that sea level varied sensitively in the Great Barrier Reef (GBR)area in response to the increase or melt of the Vostok ice cap. During the period of140-116ka BP, which was before the Last Glaciation, glaciers melt and sea level wasat a high elevation. The high value of sediment redness indicated high temperatureand precipitation prevailed in the GBR area, resulting in large amount of quartzwashed into the ocean and thus the low ratio of carbonate to quartz. As the LastGlaciation commenced, the sea level in the GBR area was generally low althoughtemperature fluctuated. In period of116-73ka BP, the low redness of sediment wassuggestive of low terrestrial input, and low total organic carbon (TOC) indicated lowocean productivity; in the period of73-58ka BP, dry and cold weather dominated inthe GBR area and sea level was relatively low. Terrestrial sandy materials were thedominant component in the sediment; In the period of58-30ka BP, precipitationbecame abundant, and wetter weather dominated in the GBR area. However, the ratioof carbonate to quartz was low, indicating high terrestrial input, which led to highocean productivity and thus high TOC. In the period of30-13ka BP, the sediment wascharacteristic of high redness, suggestive of high terrestrial input, leading to high TOC.However, concomitant with the high terrestrial input, large amount of terrestrial sandymaterials were introduced, leading to the low ratio of carbonate to quartz; Since13kaBP, the Last Glaciation terminated, while the last postglacial took place. Temperatureincreased, leading to glacier melting, high precipitation, and sea level rise. Theconcomitant terrestrial input increased, leading to high sediment redness and TOC.The high ratio of carbonate to quartz may be ascribed to low water dynamicconditions resulting from the increased water depth. The obtained results provided abaseline framework for holistic understanding of the climate-environment change inthe GBR since the Last150ka.