Dendrochronology
This dating technique analyzes the patterns of annual growth rings in trees to determine when the wood was formed.
What is dendrochronology?
This dating method relies on the magnetic properties of archaeological materials that record the Earth’s magnetic field during heating or deposition.
What is archaeomagnetic dating?
This radioactive isotope, formed when cosmic-ray-produced neutrons interact with nitrogen-14 in the atmosphere, is the foundation of radiocarbon dating.
What is carbon-14?
This fundamental molecule, which builds proteins, is central to the dating methods that share its name
What is an amino acid?
This type of volcanic material, dispersed during explosive eruptions and used as a time marker in geological studies, gives tephrochronology its name.
What is tephra?
Tree rings tend to be wider in this kind of growing season and narrower in dry or cold years.
What is a warm, wet growing season?
In archaeomagnetic dating, this term describes the gradual change of the Earth's magnetic field over decades and centuries, used to compare against archaeological samples.
What is secular variation (SV)?
Radiocarbon dating works because the intake of carbon-14 by an organism stops at this moment, starting the clock for radioactive decay.
What is the moment of death?
This period of geological time, dating from about 2.6 million years ago to the present, is the main time span over which amino acid geochronology is applied.
What is the Quaternary Period?
When volcanic glass shards from ash layers are matched to a specific eruption through chemical analysis, this kind of unique profile is being used.
What is a geochemical fingerprint?
This edge, representing the final year of growth before the bark, is essential for determining the exact felling date of a timber.
What is the waney edge?
These types of archaeological features, such as kilns, hearths, and furnaces, are commonly dated using archaeomagnetism because they record the direction and intensity of the magnetic field when last used.
What are fired structures?
This is the term for the time it takes half of the carbon-14 in a sample to decay, and it’s approximately 5,568 years as used in Libby's curve.
What is the half-life?
These specific amino acids are trapped within biomineral crystals and are chemically protected from environmental factors, allowing for more accurate dating in what is known as a "closed system."
What are intra-crystalline amino acids?
This term refers to layers of volcanic ash that are not visible to the naked eye and require detailed lab analysis to detect.
What are cryptotephras?
This statistical value, often used to assess the strength of ring-width matches between samples, must typically be above 5 or 6 for a reliable date.
What is the t-value?
This type of remanent magnetization occurs when materials are heated above their Curie temperature and then cooled, locking in the magnetic field of that moment.
What is thermoremanent magnetization (TRM)?
To detect the very low radioactivity in ancient carbon samples, Libby developed this shielding technique using iron and Geiger counters to reduce background radiation.
What is anti-coincidence shielding?
This technique can differentiate between various amino acids in ancient samples and is now the most common methods used for amino acid geochronology.
What is reverse phase high performance liquid chromatography?
High-resolution scanning using this method can non-destructively detect elemental peaks (like K, Fe, or Ca) in sediment cores that suggest the presence of tephra layers.
What is µ-XRF (micro X-ray fluorescence) scanning?
You're sampling timbers from a historic Virginia farmhouse. Most cores contain only heartwood with no sapwood or waney edge. What steps must you take to estimate the felling date and what limitations might that introduce?
What are (1) using a sapwood ring estimate based on local data to add to the last heartwood ring to create a terminus post quem, and (2) acknowledging that without sapwood or waney edge, the date range is approximate, not exact?
You uncover an ancient oven made of clay bricks during an excavation. It appears undisturbed and was clearly used for high-temperature heating. Your team wants to use archaeomagnetic dating.
What two factors must you ensure during sampling to get a reliable date?
What are (1) ensuring the bricks are sampled in situ with their orientation accurately recorded, and (2) avoiding areas that show signs of later disturbance or magnetic contamination?
You're analyzing a wooden beam from an ancient house with a known historical date. You convert the sample into carbon dioxide and count the disintegrations per minute.
You find the sample has 7 dpm per gram of carbon.
Assuming modern living matter has 14 dpm/g and a half-life of 5,568 years,
how old is the sample?
What is approximately 5,568 years old (one half-life has passed)?
You find mollus shells at a Middle Pleistocene site in northern Europe. The shells are slightly recrystallized. What key step must be taken before using amino acid dating?
What is isolate and analyze the intra-crystalline protein to ensure a closed system?
You're studying lake sediments from a maar lake in southern Italy and suspect there’s a thin, non-visible tephra layer from a distal eruption. You want to confirm its presence and identify its source.
What two major steps should you take to confirm the tephra and determine its eruption origin?
What are (1) extract and concentrate volcanic glass shards using sediment-destructive methods like sieving, chemical cleaning, and density separation, and (2) conduct geochemical analysis (e.g. EPMA) to match the glass composition with known eruption databases?