jmc 07 class1 deepseaseds post 29363

Course 12.710
Introduction to Marine Geology and Geophysics
Fall, 2007

Instructors:

Dan Lizarralde

Jerry McManus
Ken Sims

TAs:

(WHOI, Clark, 260, x 2942, )

(WHOI, Clark 121, x3328, )
(WHOI, Clark 247B, x2634, )

Lynne Elkins (WHOI, Clark 259 , x3422, )

Class Times, Places: Lectures – Tue./Thurs. 10:30-12:00, Clark237
Labs/Discussion Sections – Time TBD
Course Description: An introduction to marine geology and geophysics for non-majors. Topics include the geologic
time scale, structure of the Earth, plate tectonics, marine sedimentation and stratigraphy, depositional and erosional
processes, submarine morphology, paleoceanography, sea level changes and the evolution of the Mesozoic-Cenozoic global
ocean and climate. This course is intended for non-G&G students as a single semester course. There will be two 1 1/2 hourlong lectures each week. Problem sets will be regularly assigned and there will be weekly discussion sections and occasional
labs during the semester.
Text/Readings: Because of the breadth of topics covered there is no single textbook that is adequate for the purpose.
Lecture notes will be distributed for each class along with reading assignments in several relevant textbooks placed on
reserve or in journals. Students are responsible for the material covered in both the lectures and the reading.
Grading:

Mid-term exam - 25%
Final exam - 25%
Labs/Problem Sets - 50%


Geophysical Methods and Observations
10/25
(Lizarralde)
Seismology: Earthquakes and Earth imaging
10/30
(Lizarralde)
Potential fields, electro-magnetics, linear inverse theory
11/1
Mid Term
Sediments and Sedimentary Processes
11/1
11/6
11/8
11/13

(McManus)
(McManus)
(McManus)
(McManus)

Fluvial and coastal sedimentation
Marginal sedimentation, sequence stratigraphy
Deep-sea sediments: composition, distribution
Biological, chemical, and physical abyssal processes

Paleo-oceanography and Climate
11/15
(McManus)
Dating methods and the sedimentary record
11/20
(McManus)
Paleothermometry
11/22
Thanksgiving
11/27
(McManus)
Deep water chemistry and atmospheric p(CO2)
11/29
(McManus)
Ocean chemistry and continental weathering
12/4
(McManus)
Astronomical climate theory
12/6
(McManus)
Sedimentary records of abrupt climate change
12/11
Final Exam


Deep-Sea Sediments
I

Sources

*1. Continents
(dissolved, particulate)
2. Submarine
3. Extraterrestrial

II

Transport
1. Wind (eolian)
2. Ice
3. Water
4. Gravity

III

Composition
1. Biogenic
(opal, CaCO3, Corg)
2. Lithogenic
(clastic)
3. Authigenic
(inorganic precipitates)

IV

Distribution influences:
1. Proximity of source (size)
2. Depth of sea floor (CaCO3)
3. Seawater chemistry (opal, CaCO3)
4. Sedimentation rate (opal, Corg)

vs. Accumulation


Dust


Volcanic eruptions


Hydrothermal input

Black smoker vents (NOAA)



Water (riverine, currents)

Amazon discharge (NASA)


Wind
(eolian)

Sahara Dust (NASA)


Ice
(glaciers, sea ice, icebergs)

Classification of Marine Sediment Types
Biogenic Sediments: Remains of organisms, mainly carbonates (calcite, aragonite), opal (hydrated silica),
and calcium phosphate (teeth, bones, crustacean carpaces), also organic carbon (soft
tissues). Arrival at
the site of deposition by in situ precipitation (benthic organisms living
there) or via settling through
the water column (pelagic organisms).
Biogenic sediments are widespread on the sea floor, covering one half of the shelves and more than one half
of the deep ocean bottom (total ~55%.) They constitute ~30% of total volume of sediment being deposited.
Lithogenic Sediments: Detrital products of pre-existing rocks (igneous, metamorphic, sedimentary) and of
volcanic ejecta and extraterrestrial material. Transport by rivers, ice, winds. Nomenclature based
on grain size (gravel, sand, silt, clay). Additional qualifiers derived from the lithologic
components (terrigenous, bioclastic, volcanogenic) and from the structure of the deposits.
Fine-grained lithogenic sediments (which become shale upon aging and hardening) are the most abundant by
volume of all marine sediments (~70%) primarily due to the great thickness of continental margin sediments.
Authigenic (or Hydrogenous) Sediments: Precipitates from seawater or from interstitial water. Also
products of alteration during early chemical reactions within freshly deposited sediment.
Redissolution common. Nomenclature based on origin (evaporates) and chemical composition.
Authigenic sediments, while widespread, are not volumetrically important at present. At times in the past
they have been a much more substantial sediment component (e. g., Messinian crisis).


Biological activity
(plankton)

Arabian Sea bloom (NASA)


Thickest deposits
Terrigenous sediments delivered by rivers

Ferro-manganese
nodules
Slow-growing
Require metal input



Hjulstrom diagram
A) Transport
B) Erosion
C) Deposition



Clay minerals
rock -> chlorite (from Fe-Mg minerals) + illite (from feldspars) ->
montmorillonite -> kaolinite (in regions of high temperature, good drainage).

2NaAlSi3O8 (albite) + 2CO2 + 11H2O
↔
Al2Si2O5(OH)4 (kaolinite) + 2Na+ + 2HCO3- + 4H4SiO4


Clay type varies by
weathering regime
Chlorite ~ physical
Kaolinite ~ chemical

> 10



Biogenic sediments
a)
b)
c)
d)

Coccoliths
Foraminifera
Diatoms
Radiolarians


Organic carbon
Highly recycled:
Preservation due to
high productivity
and rapid burial.


Opal deposits
Highly recycled:
Preservation due to
high productivity
and rapid burial.
Ocean distributes.

CaCO 3 deposits
Influenced by:
Productivity and
seawater chemistry,
ocean circulation.

Carbonate content (after D. Archer))