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geoarchaeology - PowerPoint PPT Presentation

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Geoarchaeology. Studying Ancient Environments. Ancient Environments. Geology: numerous techniques for studying ancient environments (four main approaches) Petrology : studying characteristics of stone Geomorphology : studying ancient landforms Sedimentology : studying soil processes

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Studying Ancient Environments

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Ancient Environments

  • Geology: numerous techniques for studying ancient environments (four main approaches)

    • Petrology: studying characteristics of stone

    • Geomorphology: studying ancient landforms

    • Sedimentology: studying soil processes

    • Climatology: studying ancient climate change

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  • How rock changes over time (weathering, erosion)

    • Can help with determining age of material culture

  • Source Areas (where raw materials originated)

    • Thin Section Analysis

      • Looking for characteristic inclusions and crystals

      • Analysis of trade, exchange, social interaction, migration

    • Trace Element Analysis

      • X-Ray fluorescence, Neutron Activation Analysis, etc.

        • Energize sample to stimulate emission of characteristic trace element spectra; can then be tied to a source area

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Thin Section Examples



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  • Today’s landscape not always what it was in the past

    • Landscape one factor in determine available resources

      • Plants, animals, stone, etc.

      • Understanding landscape and resources helps us understand what sort of world ancient people lived in

    • Changes in landscape affect archaeological record

      • Patterns of deposition/erosion bury or destroy sites

      • e.g., Glaciation, River Erosion, Flood Deposition

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  • Nearly all archaeological sites buried

    • Need to understand soil processes

      • How deep do you have to dig? Depends on nature of soils (key to research design; determines how one surveys for and excavates sites)

        • Floodplain (deeply buried); Terrace (intermediate); Uplands (shallow deposition)

      • What comprises culturally sterile deposits?

        • North America: e.g., glacial gravels

      • Classification of soil stratigraphy

        • Plowzone (Ap), A horizon, B horizon, C horizon; “buried A horizons”

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  • Climate: another major factor in determining available resources

    • Desert, forest, swamp, prairie, etc.

  • Ecofacts: primary means of determining climate

    • Floral and Faunal Analysis

    • Dendrochronology (a record of climate as well as time)

    • Recovery by flotation

      • Seeds, microfauna, wood frags., nut frags., etc.

    • Pollen/Palynology; Phytoliths

  • Isotopic evidence

    • Stable Oxygen isotopes in Ice Cores

    • Ice Age(s) example

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Environmental Indicators



Animal Bone

Plant Remains

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Case Study in Geoarchaeology

The Sphinx:

How Old is It?

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“Great Sphinx”

  • Located on Giza Plateau, outside Cairo

    • Memphis Necropolis (includes Great Pyramids)

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Age Debate

  • Mainstream History of Monument

    • Built at same time as nearby Pyramid of Khafre (Khaf-Ra, Chephren) in about 2540 BC (face thought to be Khafre)

    • Early documentary references: 1500 BC

    • Construction of monument part of the same program monument construction during the first five centuries of the Old Kingdom (2575-2134 BC)

      • Origins of Pharaonic dynasties

      • Monuments as legitimating social hierarchy

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Age Debate

  • Controversial Reinterpretations: “Old Sphinx”

    • John Anthony West (“Amateur” Egyptologist): weathering patterns consistent with water, not wind

      • Especially for lower levels of monument (supposedly buried by sand longest, so contain most evidence of “water-weathering”)

      • Area has been arid since 10,000 BC, so Sphinx must be at least that old (and related to “Atlanteans”)

      • Some geologists (e.g., Robert Schoch) have supported the weathering theory

    • Graham Hancock: pyramids and sphinx locations relate to 10,500 BC stellar alignments

    • No recorded builder or building date (minor references that it may predate pyramids, but not by how long)

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West and Schoch

(Never trust someone wearing a pith helmet)

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Age Debate (cont.)

  • Gauri et al. (geoarchaeologists): similar patterns to West’s “water-weathering” occur in arid environments also

    • West and Schoch ignore basic geology of area

      • Sphinx carved out of local bedrock; geologic characteristics of upper layers (head) different than bottom (body) – increase in porosity in lower parts

      • salt crystals form in rock pores; causes exfoliation due to hydrostatic pressure; same patterns as West’s “water-weathering”

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Age Debate

  • Critiques of Old Sphinx argument

    • No associated artifacts older than 2,600 BC

      • If a technologically sophisticated culture existed prior to that, you would expect to find some traces beyond a single monument; Where’s their garbage?

    • West argues that Sphinx water weathered, while other monuments wind weathered

      • Why haven’t “wind weathering” patterns obliterated older, “water weathering” patterns?

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How to spot Pseudoscience

  • Prior Plausibility: how well does a theory fit with what we already know?

  • Occam’s Razor: simpler explanations should be preferred over complex

  • Non-sequitur argument: “They laughed at <insert name>, and he was right, so I must be right also”

  • Public Verifiability: can other people apply the ideas and get the same results?

  • Authority: who is the person making the argument?

  • Humility: not to say that all good scientists are humble, but a crackpot is almost never humble

  • $$$: is someone getting rich off of their claims?