Dating Methods Flashcards

Flashcards covering relative and absolute dating methods in geology and environmental science.

Lithostratigraphy

Identifies layers of rock based on their physical characteristics and position, including marker horizons.

Tephrostratigraphy

Uses volcanic ash layers to correlate and date sediment sequences.

Paleosols (Fossil soils)

Ancient buried soils that indicate former land surfaces and environmental conditions.

Biostratigraphy

Uses fossils (vertebrates, molluscs, pollen, microfauna) to relatively date sedimentary layers.

Malacothermometer

Estimates past temperatures based on climate-sensitive snail species.

δ18O of Mollusc Shells

Measures the oxygen isotope ratio to reconstruct paleotemperatures and ice volume.

Marine Microfauna

Microorganisms (e.g., foraminifera) whose assemblages reflect past ocean conditions.

Pollen Analysis

Identifies vegetation changes over time based on preserved pollen grains.

Biomarkers

Organic molecules from organisms preserved in sediments; reflect past environments.

Magnetostratigraphy

Tracks Earth’s magnetic polarity reversals recorded in rocks and sediments.

Magnetic Susceptibility (MS)

Measures how magnetized a material becomes in a magnetic field; useful in loess-paleosol sequences.

Amino Acid Racemisation (AAR)

Estimates age by measuring the conversion of L- to D-amino acids in organic remains.

Stable Isotopes (δ18O, δ13C)

Oxygen and carbon isotope ratios used for climate reconstructions and environmental analysis.

Ice Core Stratigraphy

Analyzes ice layers to infer climate, gas composition, and volcanic activity in the past.

Geomorphological Horizons

Landforms like fluvial or marine terraces used to infer relative ages and past sea levels.

Varve Chronology

Uses annual sediment layers (varves) in lakes to count years and date environmental changes.

Dendrochronology

Tree-ring dating that provides precise calendar years for wooden materials or climate events.

Potassium-Argon (K-Ar) Dating

Dates volcanic rocks using the decay of ⁴⁰K to ⁴⁰Ar, effective for old samples.

Argon-Argon (⁴⁰Ar/³⁹Ar) Dating

A more precise version of K-Ar dating using neutron activation.

Uranium-Series Dating (²³⁸U/²³⁰Th)

Dates calcium carbonate deposits like cave formations and corals.

Fission-Track Dating

Measures microscopic tracks left by the spontaneous fission of ²³⁸U in minerals.

Radiocarbon Dating (¹⁴C)

Dates organic material up to ~50,000 years by measuring radioactive carbon decay.

Thermoluminescence (TL)

Dates heated minerals by measuring light released from trapped electrons.

Optically Stimulated Luminescence (OSL)

Measures the time since sediment grains were last exposed to sunlight.

InfraRed Stimulated Luminescence (IRSL)

Similar to OSL, but used on feldspar grains stimulated by infrared light.

Electron Spin Resonance (ESR)

Measures trapped electron energy in materials like tooth enamel for age estimation.

Cosmogenic Nuclide Dating

Determines exposure age of rocks using nuclides like ¹⁰Be or ²⁶Al created by cosmic rays.