Unknown
PANGAEA
In:
Supplement to: Littke, Ralf; Fourtanier, Elisabeth; Thurow, Juergen W; Taylor, Elliott (1991): Silica diagenesis and its effects on lithification of Broken Ridge deposits, Central Indian Ocean. 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, 261-272, https://doi.org/10.2973/odp.proc.sr.121.179.1991
Publication Date:
2024-01-09
Description:
Within a dipping sequence of middle Cretaceous to Eocene sediments on Broken Ridge, opal-A, opal-CT, and quartz occur as minor constituents in carbonate and ash-rich sediments. Biogenic opal-A is mainly derived from diatoms and radiolarians. Opal-A and almost all siliceous microfossils disappear within a narrow (〈20-m-thick) transition zone below which authigenic opal-CT and quartz are present. These latter silica polymorphs occur together within a 750-m-thick interval, but the ratio of quartz/opal-CT increases with increasing age and depth within the pre-rift sediment sequence. The boundary between opal-A- and opal-CT-bearing sediments is also a physical boundary at which density, P-wave velocity, and acoustic impedance change. This physical transition is probably caused by infilling of pore space by opal-CT lepispheres.
Keywords:
121-752A; 121-752B; 121-754; 121-755A; COMPCORE; Composite Core; DRILL; Drilling/drill rig; Joides Resolution; Leg121; Ocean Drilling Program; ODP; South Indian Ridge, South Indian Ocean
Type:
Dataset
Format:
application/zip, 4 datasets
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