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Sedimentary Geochemistry

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Aqueous Geochemistry REE Patterns in Geochemistry +1 more→→Environmental Geochemistry Organic Geochemistry

Core Idea

Sedimentary geochemistry examines the chemical processes and signatures in sediments and sedimentary rocks, from their formation through weathering and transport to their burial and diagenetic transformation. Sediment chemistry records source rock composition (provenance), weathering intensity, redox conditions in the depositional environment, and post-depositional diagenetic modifications. Key tools include major-element weathering indices (CIA, CIW), REE patterns for provenance, redox-sensitive trace elements (Mo, U, V, Re) for paleoenvironmental reconstruction, and stable isotope chemostratigraphy (delta-13C, delta-34S, delta-18O) for global biogeochemical changes. Sedimentary rocks are the archive of Earth's surface conditions through time.

Explainer

Sedimentary rocks are Earth's memory. They record the chemistry of past oceans, atmospheres, weathering regimes, and biological systems in mineral assemblages, major and trace element concentrations, and isotopic compositions that can be measured billions of years after deposition. Sedimentary geochemistry reads this archive.

Provenance analysis uses immobile elements and their ratios to identify the tectonic setting and lithology of the source terrain. REE patterns (Eu anomaly, LREE/HREE slope), Th/Sc ratios (felsic sources have high Th/Sc), and Cr/Th ratios (mafic sources have high Cr) discriminate between felsic continental, mafic oceanic, and recycled sedimentary sources. These ratios survive weathering, transport, and moderate diagenesis, preserving source information in ancient sediments.

Paleoenvironmental reconstruction relies on elements whose behavior changes dramatically with redox conditions. In modern oceans, Mo, V, Re, and U are dissolved under oxygenated conditions but become insoluble and accumulate in sediments under anoxic or euxinic conditions. By measuring their enrichments in ancient sediments and calibrating against modern analogs (Black Sea, Cariaco Basin), geochemists reconstruct the redox state of past water bodies. The secular record of these elements through Earth history documents major oxygenation events, ocean anoxic events, and the long-term evolution of marine redox chemistry.

Diagenesis -- the chemical and physical changes occurring after deposition -- modifies the primary geochemical signal. Organic matter is microbially degraded through the terminal electron acceptor sequence. Pore waters evolve as minerals dissolve and precipitate. Authigenic minerals (pyrite, siderite, dolomite, glauconite) form in the sediment column. Understanding diagenesis is essential for interpreting primary signals correctly and for recognizing which geochemical proxies survive burial and which are overprinted.

Practice Questions 3 questions

Prerequisite Chain

Understanding Zero → The Number Zero → Counting to Five → Counting to 10 → Counting to 20 → Counting a Set of Objects Up to 20 → Cardinality: The Last Number Counted → Matching Numerals to Quantities → Subitizing Small Quantities → Addition Within 10 → Number Bonds to 10 → Addition Within 20 → Doubles and Near Doubles → Doubles Facts Within 10 → Near Doubles Facts Within 20 → Mental Math Strategies for Addition → Mental Math: Adding and Subtracting Tens → Addition Within 100 → Repeated Addition as Multiplication → Multiplication as Equal Groups → Multiplication: Arrays → Basic Multiplication Facts (0s, 1s, 2s, 5s, 10s) → Multiplication Facts Within 100 → Division as Equal Sharing → Division as Grouping (Measurement Division) → Division: Grouping (Repeated Subtraction) Model → Division: Fair Sharing Model → Division as Equal Sharing → Division as Grouping → Basic Division Facts → Division Facts Within 100 → Multiplication and Division Fact Families → Relationship Between Multiplication and Division → Division Facts as Inverse of Multiplication → Remainders and Quotients in Division → Division Word Problems → Multi-Step Word Problems → Solving Multi-Step Word Problems → Multiplication Word Problems → Division Word Problems → Introduction to Long Division → Factors and Multiples → Prime and Composite Numbers → Equivalent Fractions → Relating Fractions and Decimals → Decimal Place Value → Integers and the Number Line → Comparing and Ordering Integers → Absolute Value → Adding Integers → Subtracting Integers → Multiplying Integers → Dividing Integers → Unit Rates → Proportions → Percent Concept → Converting Between Fractions, Decimals, and Percents → Operations with Rational Numbers → Two-Step Equations → Solving Multi-Step Equations → Equations with Variables on Both Sides → Angle Pairs: Complementary, Supplementary, and Vertical → Parallel Lines and Transversals → Corresponding Angles → Alternate Interior Angles → Triangle Angle Sum Theorem → Exterior Angle Theorem → Triangle Inequality Theorem → Similar Triangles: AA Similarity → Similar Triangles: SSS and SAS Similarity → Proportions in Similar Triangles → Right Triangle Trigonometry Introduction → Sine, Cosine, and Tangent Ratios → Trigonometric Ratios Review → Radian Measure → Converting Between Degrees and Radians → The Unit Circle → Graphing Sine and Cosine → Graphing Tangent and Reciprocal Trigonometric Functions → Derivatives of Trigonometric Functions → Antiderivatives → Indefinite Integrals → Basic Integration Rules → Riemann Sums → Definite Integral Definition → Double Integrals: Definition and Setup → Iterated Integrals and Fubini's Theorem → Double Integrals over Rectangular Regions → Double Integrals over General Regions → Applications of Double Integrals: Area, Mass, and Moments → Triple Integrals in Cartesian Coordinates → Triple Integrals in Cylindrical and Spherical Coordinates → Change of Variables and the Jacobian Determinant → Applications of Triple Integrals: Volume and Mass → Vector Fields and Their Representations → Line Integrals of Vector Fields → Work and Circulation → Line Integrals of Scalar and Vector Functions → Fundamental Theorem for Line Integrals → Conservative Vector Fields → Conservative Vector Fields and Potential Functions → Curl and Divergence of Vector Fields → Curl and Divergence → Divergence Theorem → Electric Flux and Divergence Theorem → Gauss's Law: Integral Form and Meaning → Solving Problems with Gauss's Law → Conductors in Electrostatic Equilibrium → Capacitance and Capacitors → Dielectrics → Dielectric Constant and Relative Permittivity → Electric Field Inside Dielectric Materials → Dielectric Materials and Polarization → Dielectric Susceptibility and Permittivity → Energy Density in Electric Fields → Electric Current and Current Density → Electrical Resistance and Resistivity → Ohm's Law and Circuit Elements → Electromotive Force (EMF) and Batteries → Kirchhoff's Circuit Laws: Voltage and Current → DC Circuit Network Analysis Methods → Transient Response in RC Circuits → RC Circuits → LC and RLC Circuits → AC Circuits: Fundamentals → Impedance and Reactance → AC Power and Resonance → Electromagnetic Waves → Postulates of Special Relativity → Time Dilation → Length Contraction → Lorentz Transformation → Relativistic Velocity Addition → Relativistic Momentum and Energy → Mass-Energy Equivalence and E=mc² → Photons as Particles with Energy and Momentum → Planck-Einstein Relation: Energy and Frequency → Photoelectric Effect → The Photon: Light as Quanta → Compton Scattering → Wave-Particle Duality → de Broglie Wavelength → The Schrödinger Equation → State Vectors and Wavefunctions → Quantum Superposition → Quantum Entanglement → Bell Theorem and Bell Inequalities → Postulates of Quantum Mechanics → Observables and Quantum Operators → Commutators and Commutation Relations → Quantum Angular Momentum → Quantum Mechanical Treatment of Hydrogen → Solving the Schrödinger Equation for Hydrogen Atom → Quantum Numbers → Electron Configuration → Periodic Trends → Covalent Bonding → Electronegativity and Bond Polarity → Ionic Bonding → Lewis Structures → VSEPR Theory and Molecular Geometry → Molecular Geometry and Electron Pair Geometry → Molecular Polarity and Dipole Moments → Intermolecular Forces → States of Matter and Phase Changes: Melting, Boiling, and Sublimation → Gas Laws and the Ideal Gas Equation → Gas Stoichiometry and Volume-Volume Calculations → Thermochemistry and Enthalpy → Heat Capacity and Calorimetry → Entropy and Molecular Disorder → Spontaneity and ΔG → Entropy and Gibbs Free Energy → Chemical Equilibrium → Statistical Mechanics: Ensembles and the Boltzmann Distribution → Partition Function: Definition and Properties → The Canonical Partition Function and Thermodynamic Derivation → Free Energy and Thermodynamic Relations from Partition Functions → Legendre Transformations and Thermodynamic Potentials → Chemical Potential and Partial Molar Properties → Phase Equilibrium and Coexistence Conditions → Clausius-Clapeyron Equation → Phase Diagrams and Clausius-Clapeyron Equation → Chemical Potential and Thermodynamic Equilibrium → Geochemical Thermodynamics → Trace Element Geochemistry → Partition Coefficients → REE Patterns in Geochemistry → Sedimentary Geochemistry

Longest path: 188 steps · 1074 total prerequisite topics

Prerequisites (3)

Aqueous Geochemistryhard Redox Geochemistrysoft REE Patterns in Geochemistrysoft

Leads To (2)

Environmental Geochemistrysoft Organic Geochemistrysoft