Jim Elder

Ottawa, Canada

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Mesquite Flat Sand Dunes, Death Valley, USA

Geology: Sand & Dunes

Background

Aeolian dunes and sandstone: Overview (intro, including animations)

Strata dip and thickness: True and apparent

Numerical Models

Dune field morphology (model of migrating bedforms)

Model of stratigraphic bounding surfaces produced by migrating bedforms (stratigraphy)

Sampling dune sand (effect of sampling on grain-size distribution results)

Observations & Interpretations

Grainflow/avalanching, vortices, grainfall at Coral Pink Sand Dunes State Park, USA (videos)

Grainflow/avalanching (video)

Sand micrographs (photos of sand grains); stereogram of Navajo sand grains

Thin sections of grainflow with pinstripes

Air flow in the lee of a dune (recirculation cell)

Cornice deposit (grainfall lee of the brink)

Grainflow (slipface avalanche deposits)

Cross-sectional profile of some avalanche tongues/troughs

Coral Pink Dunes State Park, Utah, USA:

Dune migration (analysis of Google Earth imagery)

Stoss slope trenches (internal dune structure)

Serial sections (image stacks for 3D reconstructions) of rock samples:

Kanab Goldenstone (Triassic Shinarump Formation; Utah USA)

Iron-oxide concretion A (Jurassic Navajo Sandstone; Utah USA)

Iron-oxide concretion B (Jurassic Navajo Sandstone; Utah USA)

Methods

Making pinstripe laminae visible in dry sand (a refinement of Bagnold's water seep method)

Measuring cross-sectional profiles of dune features (using the shadow of a straight-edge)

Detecting subsurface slipface shear (using a sand column of contrasting colour)

Making air flow visible (using simple streamers)

Making sand flow visible using an adapted Hele-Shaw cell

Measuring dip (eg., angle of repose)

Photographic reference scale (for scale, colour, and perspective)

Protecting photographic gear from blowing sand

Enhancing low-contrast photos (post-processing to improve visibility)

Serial sectioning to obtain images for 3D reconstruction (using a rock saw)

Particle analysis: Obtaining representative subsamples (spinning riffler)

Journal articles, conference posters

Elder & Loope at Coyote Buttes, USA. Volume 25 (2), 2009

Jurassic earthquake sequence recorded by multiple generations of sand blows, Zion National Park, Utah
DB Loope, JF Elder, VA Zlotnik, RM Kettler, DT Pederson
Geology 41 (10), 1131-1134

Downslope coarsening in aeolian grainflows of the Navajo Sandstone
DB Loope, JF Elder, MR Sweeney
Sedimentary Geology 265, 156-162

An 8-event Jurassic earthquake sequence of ~1 yr duration recorded by clastic pipes and dikes within dune cross-strata, Zion National Park, Utah
DB Loope, JF Elder, VA Zlotnik, RM Kettler, DT Pederson
2012 GSA Annual Meeting, Charlotte

Origins of pinstripes and grainflow strata in eolian sandstones: Lessons from the Navajo Sandstone at Coyote Buttes, Arizona-Utah
DB Loope, JF Elder
2007 GSA Annual Meeting, Denver

Eolian pin stripes in the Navajo Sandstone: Two distinct modes of origin
DB Loope, CW Zanner, JF Elder
2005 GSA Annual Meeting, Salt Lake City

Boundary between two sets of aeolian cross-strata, Paw Hole, Utah (Navajo Sandstone)