Depositional environments beneath the shelf-edge slopes of the Great Barrier Reef, inferred from foraminiferal assemblages: IODP Expedition 325

Noriko Yagioka, Choko Nakada, Kazuhiko Fujita, Hironobu Kan, Yusuke Yokoyama, Jody M. Webster

研究成果: ジャーナルへの寄稿記事

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To understand sea-level changes since the Last Glacial Maximum (LGM) and their effects on coral reef systems, the shelf-edge slopes of the Great Barrier Reef (GBR) were cored during the Integrated Ocean Drilling Program (IODP) Expedition 325. Recovered unconsolidated sediments beneath the submerged shelf edge reefs contain abundant foraminiferal tests, which record changes in depositional environments and paleo-water depths. A total of 177 sediment samples were collected from 17 holes along three transects located within two geographical areas (Noggins Pass and Hydrographers Passage), and were analyzed to determine stratigraphic changes in foraminiferal assemblages (2–0.5 mm size fraction). Results show that four foraminiferal assemblages (A, B, C and D) are delineated by multivariate analyses (Q-mode cluster analysis and non-metric multidimensional scaling: NMDS), and these assemblages correspond to a back-reef to reef margin zone (0–10 m deep; Assemblage A), an upper photic zone (10–30 m deep) associated with hard substrates (Assemblage B), an intermediate to lower photic zone (30–90 m deep) characterized by soft substrates (Assemblage C), and a lower photic zone (90–130 m deep) only found in modern shelf slopes (Assemblage D). Gradual shifts in these four foraminiferal assemblages superimposed on a two-dimensional NMDS ordination mainly reflect water-depth gradients and the relative dominance of two substrate types (hard and soft substrates). Pre-LGM (older than Marine Isotope Stage 3: ≥MIS3) sediments along transects at Hydrographers Passage were deposited at intermediate to lower photic zones. In contrast, relatively shallow-water sequences found in ≥MIS3 deposits at Noggins Pass likely owe their origin to either turbidite and/or land slide processes. The lack of Assemblage D in ≥MIS3 deposits from all transects could be related to lowering temperature and/or increasing terrestrial influences (i.e. more light attenuation). Shallowing upward sequences found in LGM (MIS 2) deposits at Hydrographers Passage are likely related to stepwise sea-level falls to the full extent of the LGM. These foraminifer-based paleoenvironmental interpretations suggest that the GBR shelf edge slopes have changed their depositional environments continuously in response to sea-level fluctuations during the last glacial cycle.

元の言語英語
ページ(範囲)386-397
ページ数12
ジャーナルPalaeogeography, Palaeoclimatology, Palaeoecology
514
DOI
出版物ステータス出版済み - 1 15 2019

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photic zone
euphotic zone
drilling
Great Barrier Reef
barrier reef
shelf break
Ocean Drilling Program
Last Glacial Maximum
depositional environment
oceans
sea level
substrate
reefs
reef
transect
sediments
water depth
sediment
light attenuation
marine isotope stage

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

これを引用

Depositional environments beneath the shelf-edge slopes of the Great Barrier Reef, inferred from foraminiferal assemblages : IODP Expedition 325. / Yagioka, Noriko; Nakada, Choko; Fujita, Kazuhiko; Kan, Hironobu; Yokoyama, Yusuke; Webster, Jody M.

:: Palaeogeography, Palaeoclimatology, Palaeoecology, 巻 514, 15.01.2019, p. 386-397.

研究成果: ジャーナルへの寄稿記事

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title = "Depositional environments beneath the shelf-edge slopes of the Great Barrier Reef, inferred from foraminiferal assemblages: IODP Expedition 325",
abstract = "To understand sea-level changes since the Last Glacial Maximum (LGM) and their effects on coral reef systems, the shelf-edge slopes of the Great Barrier Reef (GBR) were cored during the Integrated Ocean Drilling Program (IODP) Expedition 325. Recovered unconsolidated sediments beneath the submerged shelf edge reefs contain abundant foraminiferal tests, which record changes in depositional environments and paleo-water depths. A total of 177 sediment samples were collected from 17 holes along three transects located within two geographical areas (Noggins Pass and Hydrographers Passage), and were analyzed to determine stratigraphic changes in foraminiferal assemblages (2–0.5 mm size fraction). Results show that four foraminiferal assemblages (A, B, C and D) are delineated by multivariate analyses (Q-mode cluster analysis and non-metric multidimensional scaling: NMDS), and these assemblages correspond to a back-reef to reef margin zone (0–10 m deep; Assemblage A), an upper photic zone (10–30 m deep) associated with hard substrates (Assemblage B), an intermediate to lower photic zone (30–90 m deep) characterized by soft substrates (Assemblage C), and a lower photic zone (90–130 m deep) only found in modern shelf slopes (Assemblage D). Gradual shifts in these four foraminiferal assemblages superimposed on a two-dimensional NMDS ordination mainly reflect water-depth gradients and the relative dominance of two substrate types (hard and soft substrates). Pre-LGM (older than Marine Isotope Stage 3: ≥MIS3) sediments along transects at Hydrographers Passage were deposited at intermediate to lower photic zones. In contrast, relatively shallow-water sequences found in ≥MIS3 deposits at Noggins Pass likely owe their origin to either turbidite and/or land slide processes. The lack of Assemblage D in ≥MIS3 deposits from all transects could be related to lowering temperature and/or increasing terrestrial influences (i.e. more light attenuation). Shallowing upward sequences found in LGM (MIS 2) deposits at Hydrographers Passage are likely related to stepwise sea-level falls to the full extent of the LGM. These foraminifer-based paleoenvironmental interpretations suggest that the GBR shelf edge slopes have changed their depositional environments continuously in response to sea-level fluctuations during the last glacial cycle.",
author = "Noriko Yagioka and Choko Nakada and Kazuhiko Fujita and Hironobu Kan and Yusuke Yokoyama and Webster, {Jody M.}",
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T1 - Depositional environments beneath the shelf-edge slopes of the Great Barrier Reef, inferred from foraminiferal assemblages

T2 - IODP Expedition 325

AU - Yagioka, Noriko

AU - Nakada, Choko

AU - Fujita, Kazuhiko

AU - Kan, Hironobu

AU - Yokoyama, Yusuke

AU - Webster, Jody M.

PY - 2019/1/15

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N2 - To understand sea-level changes since the Last Glacial Maximum (LGM) and their effects on coral reef systems, the shelf-edge slopes of the Great Barrier Reef (GBR) were cored during the Integrated Ocean Drilling Program (IODP) Expedition 325. Recovered unconsolidated sediments beneath the submerged shelf edge reefs contain abundant foraminiferal tests, which record changes in depositional environments and paleo-water depths. A total of 177 sediment samples were collected from 17 holes along three transects located within two geographical areas (Noggins Pass and Hydrographers Passage), and were analyzed to determine stratigraphic changes in foraminiferal assemblages (2–0.5 mm size fraction). Results show that four foraminiferal assemblages (A, B, C and D) are delineated by multivariate analyses (Q-mode cluster analysis and non-metric multidimensional scaling: NMDS), and these assemblages correspond to a back-reef to reef margin zone (0–10 m deep; Assemblage A), an upper photic zone (10–30 m deep) associated with hard substrates (Assemblage B), an intermediate to lower photic zone (30–90 m deep) characterized by soft substrates (Assemblage C), and a lower photic zone (90–130 m deep) only found in modern shelf slopes (Assemblage D). Gradual shifts in these four foraminiferal assemblages superimposed on a two-dimensional NMDS ordination mainly reflect water-depth gradients and the relative dominance of two substrate types (hard and soft substrates). Pre-LGM (older than Marine Isotope Stage 3: ≥MIS3) sediments along transects at Hydrographers Passage were deposited at intermediate to lower photic zones. In contrast, relatively shallow-water sequences found in ≥MIS3 deposits at Noggins Pass likely owe their origin to either turbidite and/or land slide processes. The lack of Assemblage D in ≥MIS3 deposits from all transects could be related to lowering temperature and/or increasing terrestrial influences (i.e. more light attenuation). Shallowing upward sequences found in LGM (MIS 2) deposits at Hydrographers Passage are likely related to stepwise sea-level falls to the full extent of the LGM. These foraminifer-based paleoenvironmental interpretations suggest that the GBR shelf edge slopes have changed their depositional environments continuously in response to sea-level fluctuations during the last glacial cycle.

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