Table T2. Lithostratigraphic summary, Site 1172.
Lithostratigraphic
units and subunits |
Series
|
Core intervals
|
Lithology
|
Depth
(mbsf) |
Comments
|
---|---|---|---|---|---|
IA | Holocene to early Pliocene | 1172A-1H to 8H;1172B-1H to 8H;1172C-1H to 8H | Nannofossil foraminifer ooze, foraminifer-bearing nannofossil ooze, and nannofossil ooze | 0-70.0 | Foraminifers decrease downsection. |
IB | early Pliocene to late Miocene | 1172A-8H to 30X;1172B-8H to 22H;1172C-8H to 18H | Nannofossil ooze | 70.0-271.2 | |
IC | early Miocene to middle Miocene | 1172A-30X to 39X;1171D-1R | Foraminifer-bearing nannofossil chalk, nannofossil chalk, clay- and foraminifer- bearing nannofossil chalk, foraminiferal-and clay-bearing nannofossil chalk | 271.2-355.8 | Increase in clay and foraminifers downsection. |
II | Oligocene to latest Eocene | 1172A-39X;1171D-2R | Diatom- and clay-bearing nannofossil chalk, silty diatomaceous claystone, spicules- and diatom-bearing clayey siltstone, diatom-bearing silty claystone, and diatomaceous clayey siltstone | 355.8-361.1 | Transitional
unit. Major lithologic changes, very slow sedimentation rates (condensed
section). |
IIIA | late to middle Eocene | 1172A-39X to 47X;1171D-2R to 3R | Diatom- and nannofossil-bearing claystone, diatom-bearing claystone, diatom claystone, and nannofossil-bearing diatom silty claystone | 361.1-433.9 | Increasing dissolution of calcareous microfossils. |
IIIB | middle Eocene | 1172A-47X to 54X;1172D-4R | Diatomaceous
silty claystone and diatom-bearing silty claystone |
433.9-503.4 | Nearly
total absence of calcareous microfossils. |
IVA | middle Eocene to early Paleocene | 1172A-54X to 56X;1172D-4R to 24R-5 | Claystone, nannofossil-bearing claystone, silty claystone, and organic-bearing silty claystone | 503.4-696.0 | Significant increase in glauconite just above the K/T boundary. |
IVB | Cretaceous (Maastrichtian) | 1172D-24R-5 to 31R | Claystone and silty claystone | 696.0-766.5 | Excellent preservation of calcareous microfossils in upper portion. |