Publication Date:
2024-01-09
Description:
We subjected 18 carbonate samples 〈1-46 Ma in age from Holes 706A, 707A, 708A, 709C, 710A, and 711A on or near the Mascarene Plateau and Madingley Rise and from Holes 712A, 713A, and 716A on or near the Chagos Bank-Maldives Ridge to instrumental neutron activation analysis to measure 32 major, minor, and trace elements and to determine the Ce anomalies (CeA*) in the carbonates relative to NASC (North American Shale Composite). Five carbonates, 32-46 Ma, yielded an average CeA* value of 0.14 ± 0.05, corrected for small (0.1%-1.8%) detrital clay particulates. This CeA* value is considered to represent the inferred CeA value in the western Indian Ocean during the 32-46-Ma interval and compares to an average CeA value of 0.05 ± 0.02 in the Pacific Ocean during the past ~35 Ma and from 93 to 97 Ma. These inferred CeA values are consistent with the Ce redox formulation proposed previously by the authors, which indirectly relates the CeA of seawater to the pH of the mixed layer.
The higher CeA* values of 0.23-0.66 in 11 carbonates, 〈1-30 Ma, indicate an inhibition of Ce + 3 oxidation to Ce(OH)4 in seawater during this interval. This observation is consistent with an enhanced transport of decayed organic debris into the Indian Ocean from the Himalayan Mountains, thereby providing a more reducing seawater environment. The postulated prominence of the Himalayas at ~30 Ma is consistent with the ODP Leg 116 observations that the voluminous sedimentation rates in the eastern Indian Ocean from the Bengal Fan existed for the past 〉24 Ma. An accelerated rise of the Himalayas may have commenced ~33-35 Ma.
Keywords:
115-706A; 115-707A; 115-708A; 115-709C; 115-710A; 115-711A; 115-712A; 115-713A; 115-716A; AGE; Aluminium; Antimony; Barium; Caesium; Calcium; Calculated; Cerium; Cerium anomaly; Chromium; Cobalt; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Dysprosium; Element analysis, neutron activation (NAA); Europium; Event label; Hafnium; Indian Ocean; Iron; Joides Resolution; Lakshadweep Sea; Lanthanum; Leg115; Lutetium; Magnesium; Manganese; Neodymium; Nickel; Ocean Drilling Program; ODP; Potassium; Rubidium; Samarium; Sample code/label; Scandium; Sodium; South Indian Ridge, South Indian Ocean; Strontium; Tantalum; Terbium; Thorium; Titanium; Uranium; Vanadium; Ytterbium; Zinc
Type:
Dataset
Format:
text/tab-separated-values, 598 data points
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