Tuesday, April 2, 2013

MUDFLATS: Superb Fossil locales of the Past and the Future?

The photo included with this post is from the Delta of the Colorado River as it enters the Sea of Cortez (also known as the Sea of California). It shows a rather special example of a mudflat environment. An essential component of most wetland ecosystems, mudflats normally form at the mouths or deltas of rivers or in lagoons; they develop near seashores where they are daily flooded by incoming tides (thus, they are also called tidal flats). The flats that now mark the mouth of the Colorado River resulted from human intervention up-river during the last century via the building of dams and heavy water usage: what once was one of the world’s greatest desert estuaries has now been transformed into nearly 1000 km2 of mudflats.

Possibly less than 0.01% of the earth’s environment today consists of mudflats. However, the rocks that form in these depositional environments seem to have a greater propensity for preservation than many other types of formations; they appear over-represented in the rock record. This is a good thing since mud flat deposits provide exceptional sites for the preservation of animal tracks and trails, plant fossils, and the stray fish, bird, or dinosaur that either died there or whose body was washed downstream, and then stranded when the tides went out.

Renowned mudflats that all geologists learn about include: The Solnhofin Limestone (lagoonal mudflats) of the late Jurassic, source rock of the famous fossil Archaeopteryx. Devonian mudflats host early amphibians along the Bay of Fundy (Blue Beach locality) and, elsewhere, the earliest land plants. The Late Precambrian (~1.4 billion years in age) Belt Formation of Montana, Idaho and Canada includes many strata initially forming as mud flats; in this era before terrestrial life, the fine silty muds preserve raindrop imprints, mudcracks, and ripple marks – features still prominently displayed within the mudflats of our modern era.

Perhaps in some geologic future, study of the Colorado Mudflat Formation will yield the fossilized tracks of off-road vehicles and the skeletal remains of abandoned fishing boats for the study of paleontologists.

Photo by Annie Griffeths Belt courtesy National Geographic http://photography.nationalgeographic.com/photography/wallpaper/mudflat-colorado-river-delta.html

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