Table T2. Lithostratigraphic summary, Site 1171.
Lithostratigraphic
unit and subunit |
Series
|
Core
intervals
|
Lithology
|
Depth
(mbsf) |
Comments
|
---|---|---|---|---|---|
IA
|
Holocene to lower Pliocene | 1171A-1H to 5H;1171B-1H to 5H;1171C-1H to 5H | Foraminifer-bearing nannofossil ooze to diatom-bearing nannofossil ooze and nannofossil ooze |
0-41.0
|
Contains
a high foraminiferal content (up to 50%). |
IB
|
lower Pliocene to lowermost Miocene | 1171A-6H to 14X;1171B-6H to 12H;1171C-6H to 25X | Foraminifer-bearing nannofossil chalk to diatom-bearing nannofossil chalk and foraminifer-bearing clay nannofossil chalk |
41.0-124.4
41.0-108.8
41.0-233.7
|
Rare
to occasional detrital silt-size glauconite caused by bottom current
action. |
II
|
Oligocene | 1171C-28X to 30X;1171D-2R to 3R | Foraminifer-bearing nannofossil chalk to foraminiferal nannofossil chalk |
253.4-272.8
257.0-269.8
|
Downsection increase in glauconite, clay, accessory minerals, quartz, radiolarians, bioclasts, sponge spicules, and volcanic glass and a decrease in biogenic carbonates. Dramatic lithologic contact at base. |
III
|
uppermost Eocene | 1171C-30X to 31X1171D-3R | Glauconitic sandy silt to clayey glauconitic siltstone |
272.8-274.8
269.8-276.2
|
Thin, highly bioturbated glauconitic unit below major lithologic transition. |
IV
|
upper Eocene | 1171D-4R to 11R | Diatom-bearing claystone, diatom and nannofossil-bearing claystone, diatomaceous claystone |
276.2-343.5
|
Alternating lithified and unlithified strata, limited recovery. |
VA
|
upper to middle Eocene | 1171D-11R to 20R | Claystone, nannofossil-bearing claystone |
343.50-421.50
|
Alternating darker and lighter strata at the decimeter to meter scale. Lighter colored intervals contain higher nannofossil and lower organic material percentages than darker intervals. There is a prominent surface at the base of this subunit. |
VB
|
middle Eocene | 1171D-20R to 26R | Claystone to occasional organic-bearing claystone |
421.50-485.70
|
Higher organic and lower nannofossil percentages in the upper and lower intervals with slightly elevated nannofossil contents and lower organic matter content within the middle section. |
VC
|
middle Eocene | 1171D-26R to 48R | Claystone, silty claystone, to nannofossil claystone |
485.70-692.49
|
Overall increase in lightness and nannofossil percentages from the unit above. High-frequency oscillations in the lighter and darker strata at the decimeter to meter scale for most of this subunit. |
VIA
|
lower Eocene | 1171D-48R to 59R | Claystone, silty claystone, nannofossil-bearing silty claystone |
692.49-805.1
|
An overall decrease in nannofossil abundance (to <1%) is accompanied by a rise in quartz silt from the unit above. |
VIB
|
lower Eocene to upper Paleocene | 1171D-59R to 75R | Organic matter-bearing silty claystone, silty claystone, organic matter-bearing clayey siltstone |
805.1-958.8
|
Quartz, organic debris, and opaque minerals increase downsection. Bioturbation diminishes downsection with laminations occurring in the last two cores. No obvious lithologic change across the Paleocene and Eocene boundary. |