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A Geologic Odyssey: Field Observations

  1. Nodules are scattered on ground surface along eroding fault scarps cutting the Sunport (Mesa del Sol) geomorphic surface (see photos and geologic setting)
  2. Nodules are only near the surface; pebbly sand below is not cemented; fault is not cemented; base of nodular zone appears to be sharp
  3. Nodules do not extend more than a few tens of meters away from the fault scarps
  4. Nodules appear to have incorporated cemented root tubules locally; others have both horizontal and vertical orientations
  5. Nodules appear to be different from nodules formed at the base of a Stage III pedogenic carbonate horizon developed in the soil at the top of the fault scarp

Transition from ancestral Rio Grande gravelly sand to overbank sand, silt, and clay with fossil snails, to calcified root mat. Overlain by eolian sheet sand with stage III pedogenic calcium-carbonate horizon developed beneath Sunport geomorphic surface south of Albuquerque, New Mexico (Locality 3)
(click image to zoom)

Exposures along the fault zone transverse to gradient of Sunport surface (Locality 2)
(click image to zoom)

Relation of fault-related nodules developed in sand to overlying pedogenic carbonate and underlying ancestral Rio Grande facies (Locality 2)
(click image to zoom)

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Definitions | Geologic setting
Field observations | Laboratory observations | Hypothesis
Develop a semi-quantitative model to test the hypothesis
Discussion and variations | Abstract | References