Shales are my passion.  They constitute approximately two thirds of the sedimentary column on Earth, and are nonetheless the least understood sedimentary rock type. The lion's share of the sedimentary rock record consists of shales and mudstones. Although still only a footnote in most soft rock curricula, there are a number of very good reasons to study shales and mudstones.
    First, in order to read the rock record correctly and at the highest detail possible, we have to learn how to "read" shales. Understanding their deposition is key to the reconstruction of past oceans, landscapes, climates, and climatic cycles. Yet, whereas students of sandstones and carbonates have been able to learn a great deal about the deposition of these rocks from studying bedforms and sedimentary structures in the context of experimental data and direct observations in modern environments, the situation is not as fortunate when we examine our current knowledge concerning shales and mudstones. The situation is changing rapidly, however, driven in part by the flume research that we are conducting at IU.
    Second, regardless whether they contain a fraction of a percent or several ten percent of organic matter, mudstones and shales are the source of the hydrocarbons that fuel the world economy. Furthermore, the seals that keep hydrocarbons in their reservoir, protect groundwater resources, and contain dangerous industrial waste products are all made of the same stuff - shales and mudstones. And finally, the technological advances in horizontal drilling and hydraulic fracturing have made it feasible to exploit the vast hydrocarbon reserves (gas and even liquids) that are stored in carbonaceous shale units in the US and elsewhere. This new reality has changed the study of shales from an academic past time to a matter of utmost economic importance.
The Economist Shale Gas & Oil Bonanza USA               The Economist - Long Term Impact of Shale Gas USA
    Third, shales are not restricted to the planet Earth. Several years ago evidence of layered rocks that show differential weathering of soft vs hard strata was discovered on Mars (Malin, M.C., and Edgett, K.S., 2000, Sedimentary rocks of early Mars, Science, v. 290, p. 1927-1937). Considering that much of the Martian sediments were derived from weathering of basalts, it is not a stretch to expect that the soft weathering intervals of Martian stratigraphy are clay dominated and consist of rocks that on Earth would be called mudstones. The 2004 MER rovers also brought us images of sediment layers that are so fine grained that they are probably mudstones, and images of flaky weathering sediments that on Earth would most likely be identified as a shale or shaley siltstone. Finally the latest rover to explore Mars, Mars Science Lab/Curiosity that touched down in August 2012, has located bona fide mudstones just 450 m distant from its landing site and is now en route to a location where we hope to find more mudstones and also sedimentary sulfate/evaporite deposits. At the moment the rover is traversing rough terrane to reach that locality, probably in the Fall of 2014. 
Image of flaky weathering rock (center) on Mars. If this were on Earth, the rock would most likely turn out to be a shale or shaley siltstone. Image from NASA web site, Spirit Rover, Sol 40. Image of "soft grinding" Mars sediments with molds of evaporite minerals. The resistance is suggestive of mudrocks. Image from NASA web site, Opportunity Rover, sol 36. Layered strata on Mars as seen with the Mars Orbiter Camera (MOC). Recessive weathering layers may bed mudstones. Image from MSSS web site.
Approaching a sandstone/mudstone contact in Yellowknife Bay (Gale Crater on Mars) with the Curiosity Rover. The harder sandstones form an overhang above the more readily eroded mudstones below. NASA/JPL/MSSS A closer view of the escarpment. Notice the white veins (filled with anhydrite) in the softer eroding mudstones. The veins give the appearance of a hydrofractured mudstone. NASA/JPL/MSSS Just the mudstones in the bottom of Yellowknife Bay. They are bedded and have resistant ledges as well as tiny concretions. NASA/JPL/MSSS

In addition to finding mudstones on Mars, the suggestion that the Hyugens probe that touched down on Titan on January 5th 2005 came to rest on a surface that consists of a mix of wet clay and ice boulders gives us hope that there are more mudstones to be found in the solar system, and possibly elsewhere. To "boldly go where no one has looked before" (to paraphrase a line from Star Trek), has been a very rewarding approach to my studies of shales and it seems that the best is yet to come. Basically I think that shales are fascinating rocks, and that there is much we can learn from them about planetary history and geologic processes. Recent funding success is making it possible now to pursue sophisticated petrographic studies by means of a state of the art environmental SEM, and experimental sedimentology with flumes specifically designed for working with muds.

My research is characterized by a holistic approach to shales, and consists of an integration of field studies (facies, stratigraphy) and lab studies (thin sections, electron microscopy, geochemistry) in order to understand the various factors that are involved in the formation of shales. Shales that I had an opportunity to study with this approach range in age from Proterozoic to Eocene and come from the Proterozoic Belt Supergroup of Montana, the Cambrian Wheeler Shale of Utah, the Ordovician Athens Shale of Alabama, the Devonian Chattanooga Shale of Tennessee, the Triassic Moenkopi Formation of Utah, the Posidonia Shale of Germany, the Mancos Shale of Utah, and the Green River Formation of Wyoming. In addition to my broad interest in shales, I am also curious about the formation of sedimentary mineral deposits and the diagenesis of sediments. (image at left  adapted from A. Matter's web site).

You can find information on research results from past projects on the Shale Studies page of this web site.

Currently I pursue five major research projects. 

  • Experimental Mudstone Deposition: Our NSF funded flume lab (currently with three 11x3m racetrack flumes) has enabled us to greatly expand this area of research and make substantial progress in our understanding of depositional processes.
  • Sequences and Parasequences in Shales: A study of the way in which shale successions are packaged and organized, and the process that are behind the outcomes we see in the rock record. One of our "laboratories" to do this are the extensive Devonian black shales in the eastern US (Chattanooga Shale, TN & KY; New Albany Shale, IN).  But we also have ongoing studies of Ordovician (Utica Shale) and Permian (Wolfcamp, TX) carbonaceous Shales. 
  • Quartz Cathodoluminescence: A study of quartz grains with SEM-CL (scanned cathodoluminescence) in order to detect provenance signatures and to utilize them for provenance studies of mudstones and shales as well as the differentiation of detrital from diagenetic quartz.
  • Microbe - Mudstone interactions: We want to understand how microbial activities affect rheology and early diagenesis of freshly deposited muds. An Environmental SEM for this research has been funded by NSF.
  • Mars Science Lab/Curiosity: Working on the MSL Science Team to direct rover activities and explore the rocks we encounter while we drive aross the floor of Gale Crater.  NASA and administered by Malin Space Science Systems.


To wish is little: We must long with utmost eagerness to gain our end.



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© Jürgen Schieber, IU Bloomington Department of Geosciences
Last updated: January 20, 2014.