12.710 Intoduction to Marine Geology and Geophysics 11/1 Mid Term Sediments, Processes, and the Sedimentary Record 11/6 (McManus) Deep-sea sediments: composition, distribution 11/8 (McManus) Biological, chemical, and physical abyssal processes 11/13 (McManus) Dating methods and the sedimentary record 11/15 (McManus) Paleothermometry 11/20 (McManus) Deep water chemistry and atmospheric p(CO 2 ) 11/22 Thanksgiving 11/27 (McManus) Ocean chemistry and continental weathering 11/29 (McManus) Astronomical climate theory 12/4 (McManus) Sedimentary records of abrupt climate change
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12.710 Intoduction to Marine Geology and Geophysics 11/1 Mid Term Sediments, Processes, and the Sedimentary Record 11/6 (McManus) Deep-sea sediments: composition,
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12.710 Intoduction to Marine Geology and Geophysics
11/1 Mid Term
Sediments, Processes, and the Sedimentary Record
11/6 (McManus) Deep-sea sediments: composition, distribution 11/8 (McManus) Biological, chemical, and physical abyssal processes
11/13 (McManus) Dating methods and the sedimentary record11/15 (McManus) Paleothermometry
11/20 (McManus) Deep water chemistry and atmospheric p(CO2)
11/22 Thanksgiving
11/27 (McManus) Ocean chemistry and continental weathering11/29 (McManus) Astronomical climate theory
12/4 (McManus) Sedimentary records of abrupt climate change
12/6 Final Exam
Abyssal sedimentary processes
I Early diagenesisPhysicalChemical Addition Removal Sed.-water interaction
II Abyssal reworkingNepheloid layersSyndepositional reworkingDeep currentsSediment drift deposits
III Bioturbation Discrete, episodic
Modeled as diffusive processVaries with depth, age, sizeEnvironmental influence
Sediment traps and bottom sedimentsComposition of settling particles not reflected on the sea floor.
Case 1. No diagenesisVariable property preserved through time at increasing depth.
Case 2. Constant diagenesisSteady state profile preserved through time at migrating depth.
Process
Compaction
Cementation
Authigenesis
Recrystallization
Inversion
Replacement
Dissolution
Bioturbation
Sequence of chemical reactions
Energy considerations yield predictable sequence.
CaCO3 more solublein the deep ocean:
Pressure effect combineswith lower [CO3=].
The (“older”) deep Pacific is more corrosive.
Pressure effect combines with lower [CO3=].
“Delta carbonate” (CO3=) is defined as difference from saturation (after Broecker).
Nepheloid layer
Turbidity increasestoward the bottom dueto resuspension.
McCave and Tucholke, 1986
Suspended load
Suspended load
Deep turbidity occurswhere western boundarycurrents provide energy.
Sediment drift deposits
Structure defined bysediment availabilityand bathymetry.