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Techlog zone
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Lithostratigraphic layer
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Key lithologies
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Primary structures
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A
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1a
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Clayey silt
Silty clay
Silty sand
Nannofossil-rich clayey silt
Biosiliceous-rich clayey silt
Nannofossil ooze
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Meter- to several tens of meters–scale alternations of biogenic component–rich clayey silt and biogenic component–poor clayey silt.
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B
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1b
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Clayey silt
Silty clay
Silt
Nannofossil-rich clayey silt
Biosiliceous-rich clayey silt
Nannofossil ooze
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Zone B is distinguished from Zone A by the lack of dark color intervals and the occurrence of laminated sediment.
Lithology is similar to that of Zone A and is characterized by the same meter-scale alternations in biogenic component abundance.
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C
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2a
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Diatom-bearing and diatom-rich clay
Clay
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This subunit is considered transitional from Zone B to the underlying Zone D, which is defined by the consistent appearance of diatom ooze.
In general, sediments in this unit are heavily bioturbated, leading to poor preservation of original sedimentary structures.
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D
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2b
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Dominated by diatom ooze (typically >70% (and as much as 95%) of the sediment)
Limited clay intervals
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Moderate to heavy bioturbation and distinctive mottling are also displayed in some sections. Tephra layers (vitric and scoriaceous) and occasional individual pumice stones are a minor but common component.
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E
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3a
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Diatomaceous ooze
Diatom-rich silty clay
Diatom-bearing silty clay
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Alternating layers that show decimeter- to meter-scale cycles of diatom ooze (relatively clay poor) and diatom-rich silty clay (relatively fewer diatoms and more clay).
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F
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3b
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Well lithified gray siliceous claystone
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Occasional parallel laminations, burrows, and carbonate concretions appear as layers and nodules.
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