07 November, 2015

Fossil roots in tuffites & bentonite deposits, Southern Germany

Yesterday I joined #FossilFriday on Twitter. It made me realize how many images of fossil roots I actually have. I am not a palaeontologist, most of them will never make it into a publication. So, let's share here! All images were taken during my doctoral research in bentonite mines in Southern Germany. The Mid-Miocene bentonite deposits of the Upper Freshwater Molasse are often associated with so called "Harte Platte" (English: hard plate) - a descriptive term for hard clay of little economic value. The hard clays are usually composed of partially altered tuffites, silified bentonite or sandstone-like horizons, and are common in deposits of a thickness of roughly 3 meters and more. While the hard clays are economically useless, their reduced shrink-swell capacity and stiffer composition is probably the reason for an often excellent preservation of fossil root features! Unfortunately, I lack the in depth palaeobotanical expertise to identify the plants they are from. However, based on their large size they must once have been quite impressive trees or shrubs that, based on the literature on depositional settings, grew in wetland settings. I also have a number of thin-sections and SEM images of well-preserved root features that I use as side-notes in an upcoming publication. But if anyone knows if it is possible to use root morphology to do more than "tree" or "shrub" let me know! The upside is always at the top of each image.

This is the image I used for #FossilFriday depicted a loam-filled root mold. It is one of the largest root molds I found.

This down-ward branching examples is part of a finely bedded, almost laminated tuffite. The tiny circular objects are sectional views of more "roots". These examples were replaced by silica.

More branching root features. Filled with a mix of loam and carbonates.

Cross-section of silica-rich root trace with central root channel? Diameter ~ 1.5 cm.

Fe-Mn-stained roots about 1 cm in diameter.

Almost vertical loam-filled root features in an almost 4 m thick tuffite.

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