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Dehn, Jonathan; Farrell, John W; Schmincke, Hans-Ulrich (1991): Geochemistry of tephra layers in ODP Site 121-758 [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.759084, Supplement to: Dehn, J et al. (1991): Neogene tephrochronology from Site 758 of the northern Ninetyeast Ridge: Indonesian Arc volcanism of the past 5 Ma. In: Weissel, J; Peirce, J; Taylor, E; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 121, 273-295, https://doi.org/10.2973/odp.proc.sr.121.123.1991

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Abstract:
A tephrochronology of the past 5 Ma is constructed with ash layers recovered from Neogene sediments during drilling at ODP Leg 121 Site 758 on northern Ninetyeast Ridge. The several hundred tephra layers observed in the first 80 m of cores range in thickness from a few millimeters to 34 cm. Seventeen tephra layers, at least 1 cm thick, were sampled and analyzed for major elements. Relative ages for the ash layers are estimated from the paleomagnetic and d18O chronostratigraphy.
The ash layers comprise about 1.7% by volume of the sediments recovered in the first 72 m. The median grain size of the ashes is about 75 ?m, with a maximum of 150 ?m. The ash consists of rhyolitic bubble junction and pumice glass shards. Blocky and platy shards are in even proportion (10%-30%) and are dominated by bubble wall shards (70%-90%). The crystal content of the layers is always less than 2%, with Plagioclase and alkali feldspar present in nearly every layer. Biotite was observed only in the thickest layers.
The major element compositions of glass and feldspar reflect fractionation trends. Three groupings of ash layers suggest different provenances with distinct magmatic systems. Dating by d18O and paleomagnetic reversals suggests major marine ash-layer-producing eruptions (marine tephra layers > 1 cm in thickness) occur roughly every approximately 414,000 yr. This value correlates well with landbased studies and dates of Pleistocene Sumatran tuffs (average 375,000-yr eruptive interval). Residence times of the magmatic systems defined by geochemical trends are 1.583, 2.524, and 1.399 Ma. The longest time interval starts with the least differentiated magma.
The Sunda Arc, specifically Sumatra, is inferred to be the source region for the ashes. Four of the youngest five ash layers recovered correlate in time and in major element chemistry to ashes observed on land at the Toba caldera.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: 5.384062 * Median Longitude: 90.361162 * South-bound Latitude: 5.384000 * West-bound Longitude: 90.361100 * North-bound Latitude: 5.384200 * East-bound Longitude: 90.361200
Date/Time Start: 1988-06-15T00:00:00 * Date/Time End: 1988-06-24T13:30:00
Event(s):
121-758 * Latitude: 5.384067 * Longitude: 90.361167 * Date/Time Start: 1988-06-15T00:00:00 * Date/Time End: 1988-06-15T00:00:00 * Elevation: -2935.0 m * Penetration: 782.2 m * Recovery: 561.9 m * Location: Indian Ocean * Campaign: Leg121 * Basis: Joides Resolution * Method/Device: Composite Core (COMPCORE) * Comment: 84 cores; 782.2 m cored; 0 m drilled; 71.8% recovery
121-758A * Latitude: 5.384200 * Longitude: 90.361200 * Date/Time Start: 1988-06-15T23:50:00 * Date/Time End: 1988-06-24T13:30:00 * Elevation: -2935.0 m * Penetration: 676.8 m * Recovery: 453.83 m * Location: Indian Ocean * Campaign: Leg121 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 73 cores; 676.8 m cored; 0 m drilled; 67.1 % recovery
121-758B * Latitude: 5.384000 * Longitude: 90.361200 * Date/Time Start: 1988-06-15T04:40:00 * Date/Time End: 1988-06-15T15:58:00 * Elevation: -2937.0 m * Penetration: 96 m * Recovery: 98.68 m * Location: Indian Ocean * Campaign: Leg121 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 10 cores; 96 m cored; 0 m drilled; 102.8 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
6 datasets

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Datasets listed in this publication series

  1. Dehn, J; Farrell, JW; Schmincke, H-U (1991): (Table 1) Major ash layers and maximum age range in ODP Site 121-758. https://doi.org/10.1594/PANGAEA.759057
  2. Dehn, J; Farrell, JW; Schmincke, H-U (1991): (Table 5) Composition of major oxides of various crystals in tephra layers at ODP Site 121-758. https://doi.org/10.1594/PANGAEA.759061
  3. Dehn, J; Farrell, JW; Schmincke, H-U (1991): (Table 2) Composition of major oxides of glass shards from ODP Site 121-758. https://doi.org/10.1594/PANGAEA.759058
  4. Dehn, J; Farrell, JW; Schmincke, H-U (1991): (Table 4) Composition of major oxides of alkali feldspar crystals in tephra layers at ODP Site 121-758. https://doi.org/10.1594/PANGAEA.759060
  5. Dehn, J; Farrell, JW; Schmincke, H-U (1991): (Table 3) Composition of major oxides of plagioclase crystals in tephra layers at ODP Site 121-758. https://doi.org/10.1594/PANGAEA.759059
  6. Dehn, J; Farrell, JW; Schmincke, H-U (1991): (Table 6) Summary of the age of major tephra layers in ODP Site 121-758. https://doi.org/10.1594/PANGAEA.759062