Skip to Main Content
When I was five I began a study of the anthills on the terraces above the Big Horn River in northwestern Wyoming. Almost immediately I found two types of ants, red ones and black ones. They differed in size, and the big red ones were the mean babies. That was about as far as I got with the ants. Although I occasionally covered a few of them with sand to test their burrowing capabilities, which are formidable, I generally left them alone. I even fed them now and then, mainly to watch their carrying ability. All in all, I believe they may have appreciated my actions; at least I wasn't bitten often.
More than a gunny sack full of sand had accumulated before my interests changed and I stopped spending so much time with the anthills. However, even today I drop down on my stomach now and then to renew old friendships.
M. Dane Picard (Grit and Clay, 1975)

Abstract

Continental subaerial (i.e., non-aquatic) deposits can be conveniently grouped into two main categories: eolianites and soil zones. A common misconception regarding such deposits is that they are devoid of fossils. Although their paleontologic record is indeed meager, distinct suites of trace fossils are present that ultimately may prove useful as diagnostic tools in identifying these environments in the rock record.

By far the most extensive geologic record of continental non-aquatic environments is that characterized by eolianites (i.e., sand dune deposits). Modern eolian sediments are associated with two major areas: (1) sandy deserts (or ergs) and (2) coastal dunes. Their identification depends primarily on the recognition of features that can be attributed to the transportation, deposition and erosion of sediment by wind.

Recent reviews on the physical characteristics of eolianites (Bigarella, 1972; Collinson, 1978c; Walker and Middleton, 1977; Ahlbrandt and Fryberger, 1982 have suggested that the following features may be diagnostic of wind-derived deposits: (a) large-scale, high-angle cross-strata (up to 35 m thick), which commonly are planar-tabular or trough to wedge-shaped; (b) high ripple indices with large bedforms showing a consistent ripple index from base to top; (e) sedimentary structures related to the process of sand avalanching down dune slip faces; (d) minor sedimentary features, including raindrop imprints, vertebrate tracks and deformation of lee-side laminae; (e) intercalated interdune deposits and/or poorly sorted lag deposits along erosional bounding surfaces; (f) frosting of sand grains; (g) large and small-scale deformation features; (h) characteristic light and heavy mineral separation ratios.

Although such sedimentologie features

Figures & Tables

Contents

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal