GEOL 4270 / 5270

Marine Chemistry and Geochemistry

Syllabus - Fall 2015 (under construction)

map of delta pCO2 during February
“The chemistry of the oceans is the chemistry of life writ large” -David Archer, U. Chicago

Meets: Tuesdays and Thursdays 11 am - 12:15 pm, Benson Earth Sciences 355
Professor: Tom Marchitto,
Office Hours: Thursdays 10-11 am in Benson 435, or by appointment

Undergrad enrollment limited to juniors and seniors
3 Credits
Counts toward the
Graduate Certificate in Oceanography

Course description: Examines the chemical, biological, geological, and physical processes affecting (and affected by) the chemistry of the oceans. Topics include: chemical cycling in seawater; chemical tracers of ocean circulation; the marine carbon cycle and its interaction with atmospheric CO2; the large-scale interdependence of nutrient distributions and biological productivity; and the chemistry of marine sediments, including early diagenesis.

Critical Concepts

This will be a lecture course. The required textbook is Ocean Biogeochemical Dynamics by Sarmiento and Gruber ('S&G'). This book will be supplemented by reserve readings from Volume 8 of Treatise on Geochemistry, 2nd Ed. ('ToG') and Schulz and Zabel's Marine Geochemistry ('MG').

Prerequisites: Introductory geology and/or oceanography; CHEM 1111 General Chemistry or equivalent; comfort with algebra and calculus (simple differentials).

Grading: 40% homework, 25% midterm exam, 25% final exam, 10% class participation including attendance. Undergraduate and graduate homework assignments and exams will be slightly different, and the two groups will be evaluated separately.

Homework: Six problem sets will allow students to apply what they have learned in class to practical problems. Math will generally be limited to algebra and basic calculus. Homework assignments are to be handed in during class (generally one week after being assigned), and late assignments will lose 10% credit per day (not per class meeting). If late assignments are left in Marchitto's GEOL mailbox, they must be stamped Received by a member of the office staff during business hours.

Exams: Midterm and final exams will include short answer and (for graduate students) longer answer questions, and will stress, but are not limited to, Critical Concepts. The Final will focus on material covered after the Midterm


Religious or other obligations: If you have any conflicts with scheduled exams because of religious or other obligations, please notify me at least two weeks in advance of the conflict to request special accommodation. See Registrar's policy on final exam conficts (three on same day).

Disabilities: If you qualify for accommodations because of a disability, please submit to me a letter from Disability Services within the first two weeks of class, so that your needs may be addressed. Disability Services determines accommodations based on documented disabilities.

Note on academic honesty: Students are allowed to work together on homework problems, but are not allowed to simply copy each other’s work. Copying constitutes cheating under the CU Honor Code.


Class Schedule and Reading
Reading assignments include all subsections within a listed section, unless otherwise noted
Click on lecture title for PowerPoint file (available after each lecture, password protected)

T 8/25: Introduction to marine chemistry and geochemistry
introduction, collecting seawater, collecting sediments
No reading

Th 8/27: Composition of seawater: Major elements
principle of constant proportions, salinity, 1-box model, steady state, residence time
Read S&G 1.1

T 9/1, Th 9/3: Catalina Foram Workshop - No Class

T 9/8: Sources, Sinks, & Ions
inputs & outputs, periodic tables, d0/d10/transition cations
Read Railsback (2003) accompanied by this table (with more info here)

Th 9/10: Internal cycling of elements
non-conservative behavior, biological cycling, 2- and 3-box models
Read S&G 1.2-1.3
Nozaki's periodic table of dissolved elements in the Pacific
MBARI periodic table of elements in the ocean

T 9/15: Tracing upper ocean circulation
density stratification, ventilated thermocline, tritium, 3He, CFCs
Read S&G 2.3
1st Homework due

Th 9/17: Tracing deep ocean circulation
water masses, radiocarbon, PO4*, meridional overturning circulation
Read S&G 2.4

T 9/22: Air-sea exchange
Henry's law, stagnant film model, wind speed dependence, 14C and 222Rn methods
Read S&G 3.1-3.3

Th 9/24: Biological primary production
photosynthesis, measurement, nutrient supply, light, biological pump efficiency
Read S&G 4.1
2nd Homework due

T 9/29: Limiting nutrients
Redfield ratio, trace metal biogeochemistry, Fe fertilization, phytoplankton
Read S&G 4.2 up through "Phytoplankton distribution and productivity," & read "The role of iron" on pp. 160-162

Th 10/1: Organic matter in the water column
POM & DOM, remineralization, AOU & OUR, sinking
Read S&G 5.1-5.2 & 5.4

T 10/6: Nitrogen and phosphorous cycles
phosphate, nitrification, denitrification, N fixation
Read S&G 5.3
3rd Homework due

Th 10/8: Silicate cycle
diatoms, opal export, silicic acid distribution, Si*
Read S&G 7.1-7.3

T 10/13: Midterm Exam

Th 10/15: Carbonate system in seawater
electroneutrality, pH, alkalinity, DIC
Read S&G 8.1-8.2
Good book for more details: CO2 in Seawater: Equilibrium, Kinetics, Isotopes by Zeebe and Wolf-Gladrow
Carbonate system calculator (CDIAC)

T 10/20: Ocean pCO2
DIC & Alk distribution, pCO2 systematics, pCO2 seasonality
Read S&G 8.3

Th 10/22: CaCO3 cycling
coccoliths/foraminifera/pteropods, CaCO3 solubility, lysocline/CCD
Read S&G 9.1-9.4
4th Homework due

T 10/27: Anthropogenic CO2 invasion
global carbon cycle, Revelle factor, ocean acidification
Read S&G 10.1-10.2
Ocean Acidification Network
WHOI Ocean Acidification

Th 10/29: Stable isotopes of C and N
d13C, air-sea d13C, d15N, denitrification
Read C-13 and N-15 sections of Marchitto, 2013

T 11/3: Radiocarbon

Th 11/5: U-series radionuclides
decay chains, U-Th dating, 210Pb sed rates, particle tracers
Read sections 6.09.2, 6.09.5-, 6.09.7- of Anderson, 2003

T 11/10:Marine sediments
particle size, biogenic, terrigenous, authigenic
Read MG Chapter 1 by Futterer
5th Homework due

Th 11/12:Pore water chemistry and diffusion
pore water profiles, diffusion
Read MG Chapter 3-3.2.3 by Schulz

T 11/17: Bacterial oxidation of organic matter in sediments
redox, half reactions, diagenetic sequence, bacteria
Read ToG 6.11.2 by Emerson & Hedges

Th 11/19: Fe, S, and Mn redox cycles
seawater redox potential, Fe oxides, pyrite, Mn nodules
No reading

T 11/24, Th 11/26: Fall Break - No Class

T 12/1: Hydrothermal systems
water-rock interaction, phase separation, mineral deposits, chemosynthetic ecosystems
Read ToG 6.07.2-6.07.4 by German & von Damm
6th Homework due

Th 12/3: History of ocean chemistry and the rise of cyanobacteria
banded iron formations, rise of O2 & sulfate, seafloor spreading cycles, cyanobacterial modification of seawater
Read ToG 6.21.1- by Holland

T 12/8: Cenozoic weathering and atmospheric CO2
CO2 degassing vs. weathering, Sr isotopes, Os isotopes
Read ToG 6.20.3, 6.20.6 by Ravizza & Zachos

Th 12/10: Last Glacial Maximum ocean chemistry

M 12/14 (1:30-4:00 pm): Final Exam