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Ghost Ranch, New Mexico, Project Overview – GEO 660, Summer 20006

Ghost Ranch, New Mexico, Project Overview – GEO 660, Summer 20006. Physical Response of Aeolian Sands Seas to Changes in Wind Regime Over the Last 100,000 Years – An Approach From System Self-Organization. Gary Kocurek. Overview of project Your preparation

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Ghost Ranch, New Mexico, Project Overview – GEO 660, Summer 20006

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  1. Ghost Ranch, New Mexico, Project Overview – GEO 660, Summer 20006 Physical Response of Aeolian Sands Seas to Changes in Wind Regime Over the Last 100,000 Years – An Approach From System Self-Organization Gary Kocurek

  2. Overview of project Your preparation More time in field looking at the geology and less lecture Objectives of Pre-Class Meeting

  3. Regional paleogeography Review of aeolian systems and their rock record Ghost Ranch Project Middle Jurassic Entrada & Todilto Formations What is unique about Entrada dune record Some parts of the explanation Project assignment Topics Addressed

  4. Middle Jurassic World View

  5. Western North America • Subduction complex • Interior seaway • Entrada Desert

  6. Entrada Sand Sea (In Part!)

  7. Entrada & Todilto Paleogeography

  8. Todilto Formation Facies • Inland sea • Bull’s eye facies pattern • Surrounded by Entrada dunes • Marine and sabkha facies to north and west

  9. Ghost Ranch Outcrop

  10. What Is The Rock Record Of Migrating Aeolian Sand Dunes?

  11. Ancient Aeolian Record • Sets of dune cross-strata • Each set is produced by one migrating dune • Transport direction determined by foreset dip directions • Interdune surface and overlying flat interdune strata

  12. Ancient Aeolian Record

  13. Ancient Aeolian Record

  14. Stratification Types of Dune Foresets • Lee-face deposits • Grainflow • Grainfall • Wind ripples • Textural differences reflected in diagensis

  15. Grainflow & Grainfall Strata

  16. Grainflow & Wind-Ripple Strata

  17. Wind-Ripple Laminae

  18. Grainflow Cross-Strata

  19. Grainflow, Wind-Ripple & Flat Strata

  20. Ghost Ranch Outcrop: What Is Special Regarding Dune Preservation?

  21. Entrada/Todilto Outcrop • L & G are Todilto facies • M represents subaqueous mass flow deposits • D is the last Entrada dune • Compare D to underlying Entrada strata

  22. “Right” Wall of Entrada/Todilto Outcrop

  23. “Left” Wall of Entrada/Todilto Outcrop

  24. Todilto Facies I: Well Laminated Limestone

  25. Todilto Facies I In Thin-Section

  26. Todilto Facies II: Brecciated Laminae Limestone

  27. Todilto Facies III: Wavy Laminae Limestone

  28. Todilto Facies IV: Micro Laminae Limestone

  29. Todilto Facies V: Gypsum

  30. Explain the occurrence of preserved Entrada dune paleo-topography (one of 3 known examples globally!) Components Draw for yourself the outcrop walls of the Entrada & Todilto By a series of connected measured sections, document the relationship of the Todilto facies to the Entrada paleotopography Interpret/contrast depositional settings of Entrada dune, mass flows, and Todilto facies What to hand in Two drawings No more than 2 pages of text that gives your interpretation with support (exclude irrelevant material!) Ghost Ranch Project

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