Course 12.710Introduction to Marine Geology and Geophysics

Fall, 2007

Instructors: Dan Lizarralde (WHOI, Clark, 260, x 2942, danl@whoi.edu) Jerry McManus (WHOI, Clark 121, x3328, jmcmanus@whoi.edu)

Ken Sims (WHOI, Clark 247B, x2634, ksims@whoi.edu)

TAs: Lynne Elkins (WHOI, Clark 259 , x3422, lelkins@whoi.edu)

Class Times, Places: Lectures – Tue./Thurs. 10:30-12:00, Clark237Labs/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 hour-long 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 Observations10/25 (Lizarralde) Seismology: Earthquakes and Earth imaging10/30 (Lizarralde) Potential fields, electro-magnetics, linear inverse theory

11/1 Mid Term

Sediments and Sedimentary Processes

11/1 (McManus) Fluvial and coastal sedimentation11/6 (McManus) Marginal sedimentation, sequence stratigraphy11/8 (McManus) Deep-sea sediments: composition, distribution11/13 (McManus) Biological, chemical, and physical abyssal processes

Paleo-oceanography and Climate

11/15 (McManus) Dating methods and the sedimentary record11/20 (McManus) Paleothermometry11/22 Thanksgiving11/27 (McManus) Deep water chemistry and atmospheric p(CO2)11/29 (McManus) Ocean chemistry and continental weathering12/4 (McManus) Astronomical climate theory12/6 (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).

Arabian Sea bloom (NASA)

Biological activity(plankton)

Thickest depositsTerrigenous sediments delivered by rivers

Ferro-manganesenodules

Slow-growingRequire metal input

Hjulstrom diagramA) TransportB) ErosionC) Deposition

Clay mineralsrock -> chlorite (from Fe-Mg minerals) + illite (from feldspars) ->

montmorillonite -> kaolinite (in regions of high temperature, good drainage).

Clay mineralsrock -> chlorite (from Fe-Mg minerals) + illite (from feldspars)

2NaAlSi3O8 (albite) + 2CO2 + 11H2O

Al2Si2O5(OH)4 (kaolinite) + 2Na+ + 2HCO3- + 4H4SiO4

Clay type varies by weathering regime

Chlorite ~ physicalKaolinite ~ chemical

> 10

Biogenic sediments

a) Coccolithsb) Foraminiferac) Diatomsd) Radiolarians

Organic carbon

Highly recycled:

Preservation due tohigh productivityand rapid burial.

Opal deposits

Highly recycled:

Preservation due tohigh productivityand rapid burial.Ocean distributes.

CaCO3 deposits

Influenced by:

Productivity andseawater chemistry,ocean circulation.

Carbonate content (after D. Archer))

Intra-basin ocean circulation

Biology andPhysics influenceChemistry

Circulation sweepsnutrients toward thePacific, andproductivity tends totrap them there.

From Atlantic toPacific Ocean:

Oxygen declines andsilica increases inthe deep water.

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).

Sedimentary sequenceevolves through time.

Sediment cores will reflectthat evolution, and can beused for reconstruction.