Slashdot Mirror

← Back to Stories (view on slashdot.org)

World's Largest Fossil Forest, and One of the Oldest

Posted by kdawson on from the like-insects-in-amber dept.

solitas writes in with news from last week of the discovery of a fossilized forest in Illinois. The forest was found in the ceiling of a working coal mine, 250 feet below the surface. It was drowned 300 million years ago in an earthquake, its discoverers speculate — here is a graphic of its formation. Geologists are excited because the huge fossilized forest, over 25 square miles in extent, preserves trees and other plants upright, as they grew.

5 of 245 comments (clear)

  1. Some background information for folks. by slashdotsyncline · · Score: 5, Informative

    Hi,

    One of the authors here (Scott Elrick - geologist from the Illinois State Geological Survey). I would be happy to answer questions from folks... or at least try!

    I can start by giving a basic overview of the discovery, what we found, and how it is important (to paleobotanists that is).

    The location of the fossils is just to the south and west of Danville, IL, itself about 30 miles to the east of the University of Illinois, Urbana-Champaign (say hi to HAL when you come to visit). The forest was found directly above the Herrin coal seam in the Riola and Vermillion Grove coal mines, owned by Black Beauty coal (a subsidiary of Peabody Energy). The mines cover approximately 15 square miles and the study area was about 4 square miles... actually 1000 hectares. (I'm rounding up the square miles)

    Okay, so what's so cool? If you are a geologist and read the headlines that have been popping up about the story, you may have scoffed and shook your head saying, "What do they mean largest fossil forest? A coal seam is nothing but the fossil remnants of a fossil forest. And a coal seam like the Colchester coal extended from Pennsylvania all the way to Oklahoma!" And you are correct! (This is my first exposure to the modern day media... and its been an eye opener! Give them credit, they do a pretty god job overall)

    What is 'largest' about this fossil forest story is that it is the largest STUDY of a mostly entact fossil forest. Specifically one that is looking at the ecology of that forest. The largest study before this that looked at the overall ecology was about 25 hectares.. say about 1/10th of a square mile. So this study is an order of magnitude greater. The meat of the matter here is that we had an opportunity to examine a fossil forest at just a wonderfully huge scale and as a result were able to see subtle changes in the make-up of the forest as we walked the multiple miles of passageways in the mine.

    The analogy is that previous studies were like blindfolded people examining an elephant. Each person has a wonderfully detailed and accurate description of his or her patch of the elephant, and when they compare notes a decent group consensus exists as to what the elephant probably looks like... but nobody has a chance to see the whole elephant. Our study is where we get to step back from the elephant a bit and take a pretty good peak under the blindfold at the whole animal. (I wont go so far as to say we are able to clearly see the whole thing as that is stretching the analogy. The point being it is an important and exciting step forward, but not necessarily a monstrous revelation!)

    A couple of things to highlight.

    First, the part that I find the coolest about work like this. In much of geologic science (field aspects more so), geologists look at vast spreads of time in small geographic slices. For example, standing at the rim of the Grand Canyon and peering across to the other side, your eye takes in millions of years of geologic time... but you are only able to see a thin 'slice' of each unit in profile. What does a particular rock unit look like 500 feet into the side of the canyon walls? The only way to find out is to drill a hole and take a core sample.

    Geologic research, or in this case paleontological research, in an underground mine such as these coal mines is orthogonal to the norm above! At these mines, looking up at preserved trees and ferns in the mine ceiling, we were looking at single slice of time, a T(0) event, over a huge (relatively speaking) geographic area. That means that we were able to get a snapshot in time look at the forrest landscape of 300 million years ago. It's the 'worms eye' view of a fossil forest.

    I should point out that the 'discovery' of this fossil forest was a gradual process. One of the responsibilities of the Illinois State Geological Survey is to try to understand the geology of the state of Illinois... and for us in the coal section that means coworker John Nelson and I (also one of the aut

    1. Re:Some background information for folks. by slashdotsyncline · · Score: 4, Informative

      An excellent question Assassin bug,

      I've had a few emails on the very topic.

      Howard Falcon-Lang and Bill Dimichele did find Eurypterid parts and pieces for certain and in some 'hashy' areas we may have found insect parts but it was hard to tell. Truthfully, the study area was so dang large that we were forced to really 'make tracks' to cover what we could, I am certain short-changing areas of interest such as your own in favor of the dominant plant fossils. I think I described the task to one reporter as trying to make a map of all the store fronts in New York city in a few days of walking the city, ending up with your 'chinatown area' ' little italy area' etc..

      A shame now in retrospect that we didn't make more of an effort to look for those other parts of the system... but oh baby did we have a lot of ground to cover!

      We do have representative samples from the mine roof that are currently in the Smithsonian collection, and hopefully Grimalidi can snag some time to give them a look over.

    2. Re:Some background information for folks. by slashdotsyncline · · Score: 4, Informative

      Assassin bug asked nearly the same thing. We did find Eurypterid (http://en.wikipedia.org/wiki/Sea_scorpion) pieces mixed in with the plant fossils and there is the possibility of some insect parts (legs, etc..) in some of the 'hashier' areas of the roof.

      But, as I mentioned to Assassin bug, we had a LOT of territory to cover in fairly short amount of time, so we had to concentrate on the dominant plant fossils.

      Your speculation on the moveable critters in the system 'getting the heck out of dodge' when the ground dropped out from underneath them may well be true. I would hope that at least some died and stayed put! Time (to collect data) was our enemy here.

      I should probably have mentioned this before, but we are very thankful that Peabody Energy allowed us into the mine to study and record this wonderful fossil forest. It costs them man power and time to shepard us in their mines and they have been very supportive of our efforts. Truthfully, without them extracting the coal in the first place, we would never have been able to see the steady unveiling (10 years time!) of this 300 million year old snapshot in time.

    3. Re:Some background information for folks. by slashdotsyncline · · Score: 5, Informative

      Yes!

      We should have a website with detailed pictures and explanatory text online this by this Friday at the Illinois State Geological Survey home page:

      www.isgs.uiuc.edu

      look for a link on the 'recent news' portion.

      (now guess what I get to do all day tomorrow...)

    4. Re:Some background information for folks. by slashdotsyncline · · Score: 5, Informative

      Hi Richard!

      It's a pleasure to be posting. I have been a super-ultra-long-time-gets-the-funny-all-your-base -jokes lurker for just about forever.

      Part one of your question is asking if the catastrophic event of earthquake induced flooding be destructive to forest-floor plants. A very good question.

      To answer that I'll steal some text that will be going on the website this Friday as written by Bill DiMichele to describe the ground cover plants and follow up afterward:

      "Ground cover plants:

      Plants inferred from their growth forms to have been ground cover are not common at Riola. This suggests that the soil surface may have been inhospitable to the growth of small plants, perhaps due to flooding.

      One plant in particular, Sphenophyllum, was widespread throughout the mine but rare. Sphenophyllum (Images 51 & 52) is a sphenopsid, the same higher-level group that includes the horsetails. Like that group of plants, it has "node-internode" construction and its leaves and branches are borne in whorls. In this instance, however, the leaves are wedge-shaped, a distinctive attribute of these plants. Some Sphenophyllum species have hooks or barbs on their leaves, suggesting that they too formed thickets or tangles, and perhaps may have climbed other trees for support.

      Another potential ground cover plant, a possible small fern or seed plant, is Sphenopteris (Image 53), which is rare in the Riola mine. Sphenopteris is characterized by small fronds that have small, variously lobed pinnules."

      One reason to believe that the flooding, while catastrophic in the sense that it was sudden, may not have been particularly violent is the lack of strong linear orientation of both plants and logs, nor any preferred 'piling' of leaf litter and debris up against upright tree stumps. I personally would imagine the flooding of the forest to be in the multiple minutes category and not the 'large imposing' violent wave category. As Bill writes above, the ground surface may not have been conducive to thick luxuriant cover, but I also wonder to what degree the Sphenophyllum 'hooks and barbs' may have rooted them in place under flooding duress!

      The second part of your question asks about the importance of smaller life being critical to an understanding of forest ecology.

      You got that right! In modern forests the importance of 'smaller life' is undeniable.

      In geology we are often forced by lack of data to fill in the gaps as best as we are able to infer. Or we are required to 'complete the puzzle' with the available puzzle pieces. Along those lines, much of the picture of these 300 million year old peat mires comes about through many many many individual finds and discoveries. A few insects here... an amphibian there... ground cover plants here... massive monster of tree there... a complete coal ball collection detailing plant diversities and general ecologies here... glimpses of many of these individuals (but not all unless you've got good karma) together in one spot there... etc.. Put all the individual puzzle pieces together and a cohesive picture starts to form.

      For this particular study I feel pretty confident in saying that we are almost certainly missing big chunks of 'the little stuff'. For example, we may have seen some insect parts, but we can't be sure. Did they get swept away? Fly away? Hard to know. We are absolutely missing the entire ecological picture here and in that sense the answer to your question is a disappointing, "Nope, we don't have it all, so we don't have the honest to gosh whole picture"

      But what this study does provide is some confirmation that the picture we have theorized about... i.e. we think the Pennsylvanian peat mire ecology looks like 'X' is correct. That the subtle variations in forest ecology that you would see walking down a hiking trail in your nearby state park ("Hmm, first I saw maples, and 300 feet later I saw a few oaks, and then the maples thinned out and the oaks were dominant"