Basic background for the geo- and archaeo- magnetist. Time scales Stratigraphy Site types Material types Field methods

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1 Basic background for the geo- and archaeo- magnetist Time scales Stratigraphy Site types Material types Field methods

2 Field Observations Geology Archaeology

3 Materials Geology Rocks and minerals Archaeology Material culture Minerals are the building blocks of rocks; they are inorganic, naturally occurring solid substance with definite chemical composition and orderly internal crystal structure Material culture refers to the artifacts or other concrete things left by past cultures

4 Time Scales The Earth: 4.6 billion years Oldest rocks: ~ 4 billion years

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8 Formation Processes Law of superposition: Sedimentary layers are deposited in a time sequence, with the oldest on the bottom and the youngest on the top. Uniformitarianism: "the present is the key to the past,"

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12 Measuring Time Relative vs. Absolute Dating Today - for prehistory and more and more historical archaeology, radioactive clocks are most important Neutral international system of dating - Scientists using radioactive clocks have chosen to count back from before present (BP). The fixed date selected was the approximate date when radiocarbon dating first established.

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17 Contextual seriation: Flinders Petrie s own serial ordering of! predynastic Egyptian pottery from the site of Diospolis Parva.! Starting at the top, seven successive stages are identified,! each linked to the one before and after by at least one similar shape.! At the left of the five lower rows are the wavy-handled pots,! arranged by Petrie in a sequence of degradation! his clue to the order of the whole series. Subsequent research in Egypt! has largely supported Petrie s relative chronological sequence.

18 Frequency Seriation: Relies mostly on measuring changes in the proportional abundance or frequency of design changes through time. Frequency seriation: changes in the popularity (or frequency) of three! tombstone designs in central Connecticut cemeteries, from 1700 to 1860.! Rises and falls in popularity have produced the characteristic battleship-shaped curve for the fluctuating fortunes of each design. As elsewhere in New England, the Death s head design (peak popularity ) was gradually replaced the Cherub (peak ) which in turn was replaced by the Urn and! willow tree (peak ).

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20 Years ago ,000 0 Calendars Varves Tree Rings Thermoluminescence & Optical Dating Archaeomagnetism Cation ratio 20,000 Radiocarbon Obsidian Hydration 50, ,000 Electron spin resonance Uranium series Aminoacid racemization 500,000 1,000,000 Potassium argon Geomagnetic reversals Fission track 5,000,000

21 The Long Master Sequences and Radiocarbon Dating Direct Tree Ring Dating

22 Newly Cut Tree Beam from a house 1940 Beam from an older house

23 Radioactive Clocks based on radioactive decay. 14C is best known and useful for archaeologists (+50,000 years) Poor sampling & careless interpretation = errors Willard Libby 1949 devised use of Geiger counter to measure emissions of decaying beta particles Conventional (10 20 gr) vs Accelerator Mass Spectrometry (AMS = 5 10 mg samples) counts atoms directly

24 14C has 6 protons and 8 neutrons in the nucleus of atom

25 On-line Calibration programs CALIB Radiocarbon Calibration M. Stuiver, P.J. Reimer, and R. Reimer HTML version 4.2 Execute at University of Washington Execute at Queen's University of Belfast OXCAL Radiocarbon Calibration Oxford Radiocarbon Accelerator Unit Research Laboratory for Archaeology and The History of Art

26 Contamination and Interpretation of Radiocarbon Samples * Contamination before sampling * Contamination during or after sampling * Misunderstanding of Context (formation processes * Mistakes in relative dating of context (old charcoal in secondary context)

27 Calibrating 14C Dates with the Dendrochronological record * Establishing absolute dates for radiocarbon determinations Radiocarbon date = /- 200 BP 95% chance sample Date falls between c. 405 Cal BC and 5 Cal BC.

28 95% probability event Occurred between 550 Cal BC and 50 Cal BC Gaussian or Normal Curve Calendar age ranges with very irregular probability distributions

29 Sites

30 Tabun Cave, Israel

31 Baths of Caracalla (caldarium)

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35 Earth s structure, plate tectonics

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38 Stratigraphy Law of superposition Uniformitarianism Pleistocene Holocene Neolithic (agricultural revolution) Chalcolithic (metallurgical revolution) Seriation and ceramic typology 14C Igneous rocks Sedimentary rocks Crust-Mental-Core Relative chronology Absolute chronology Mineral Material culture