Bøe, Reidulv (1994): Petrology and geochemistry of sedimentary Unit III of ODP Hole 135-840B [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.787686, Supplement to: Bøe, R (1994): Nature and record of Late Miocene mass-flow deposits from the Lau-Tonga forearc basin, Tongan Platform (Hole 840B). In: Hawkins, J; Parson, L; Allan, J; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 135, 87-100, https://doi.org/10.2973/odp.proc.sr.135.107.1994
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Abstract:
The sedimentary sequence recovered at Site 840, on the Tonga frontal-arc platform, is 597.3 m thick and is subdivided into three lithostratigraphic units. The lowermost, late Miocene Unit III is 336.8 m thick and consists of a sequence of volcaniclastic mass-flow deposits (predominantly turbidites) interbedded with pelagic/hemipelagic deposits.
Unit III was deposited in the forearc basin of the Lau volcanic arc, probably on a slope dominated by mass flows that built eastward from the ridge front and across the forearc. Upward through the unit a thinning and fining of individual turbidites takes place, interpreted to reflect a reduced sediment supply and a change from large to smaller flows. Decreasing volcanic activity with time is inferred from a decrease in coarse-grained volcaniclastic content in the upper part of the unit. The majority of the turbidites show the typical Bouma-type divisions, although both high- and low-density turbidity currents are inferred. High-density turbidity currents were especially common in the lower part of the unit.
Geochemical analyses of detrital glass lie mainly in the low-K tholeiite field with a compositional range from basalt to rhyolite. A coherent igneous trend indicates derivation from a single volcanic source. This source was probably situated on the rifted part of the Lau-Tonga Ridge, within the present Lau backarc basin. The initial opening of the Lau Basin may have been around 6.0 m.y. ago. The onset of more extensive rifting, approximately 5.6 m.y. ago, is reflected in an increase in the silica content of volcanic glass. At the boundary toward Unit II, at approximately 5.25 Ma, an influx of thicker bedded and coarser grained volcaniclastic material is interpreted to reflect increasing volcanism and tectonism during the final breakup of the Lau-Tonga Ridge.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Latitude: -22.221000 * Longitude: -175.749000
Date/Time Start: 1991-01-25T02:53:00 * Date/Time End: 1991-01-29T12:10:00
Event(s):
135-840B * Latitude: -22.221000 * Longitude: -175.749000 * Date/Time Start: 1991-01-25T02:53:00 * Date/Time End: 1991-01-29T12:10:00 * Elevation: -755.0 m * Penetration: 597.3 m * Recovery: 176.2 m * Location: South Pacific Ocean * Campaign: Leg135 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 63 cores; 597.3 m cored; 0 m drilled; 29.5 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
3 datasets
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Datasets listed in this publication series
- Bøe, R (1994): (Table 4) Analyses of detrital volcanic glass grains from Unit III of ODP Hole 135-840B. https://doi.org/10.1594/PANGAEA.787685
- Bøe, R (1994): (Table 2) Petrography of volcaniclastic sandstones from Unit III of ODP Hole 135-840B. https://doi.org/10.1594/PANGAEA.787683
- Bøe, R (1993): (Table 3) Analyses of detrital plagioclase grains from Unit III of ODP Hole 135-840B. https://doi.org/10.1594/PANGAEA.787684