Indiana University Research & Creative Activity January 1998 Volume XX Number 3


Transforming Geological Field Work

Brian Keith and Todd Thompson have a book that they want "lumpers" and "splitters" to cut in half, get dirty, and hose off. It is the Corebook of Pennsylvanian Rocks in the Illinois Basin, the first publication that offers an easy to-use identification and labeling system for both scientists and energy explorers. It works like a field guide for birds, only it is for use with cores. And it could make a big difference even for people who never see the book.

Imagine having a well drilled in your back yard to explore for coal. In the report, the driller describes the subsoils and types of bedrock in the core sample. But the driller uses terminology that causes the mining company not to notice that your property has valuable mineral deposits. Such a scene has occurred more than once in prospecting for oil, gas, water, and coal; but with the development and publication of the Corebook by scientists from the Indiana Geological Survey (IGS), such misadventures might fade away.

"Coal companies have few geologists on their staffs," said Brian Keith, a senior scientist at the IGS and an associate professor of geological sciences at Indiana University Bloomington, who led the team that completed the Corebook. "They have a lot more drillers than geologists, and most of those were trained by the previous driller, who was trained by the driller previous to him, and so on. Many of the features the geologists wanted to see weren't being reported by the drillers because they just didn't know what to look for or how to report it." But by creating a standardized system for reporting on the contents of core samples, and by teaching drillers and others how to use the system in a series of all-day, hands-on workshops, an IGS team has made it possible for virtually anyone to identify and describe the contents of most core samples in the Illinois-Kentucky-Indiana area. The team includes Keith; Todd Thompson, an associate scientist; Maria Mastalerz, a coal geologist/sedimentologist; Erik Kvale, a research scientist; and Norman Hester, a professor of geological science at IUB, state geologist, and the director of the Survey.

The coding system the team devised is intuitive and simple, beginning with the bedrock's major characteristic (sandstone, limestone, shale, coal, etc.), then describing finer characteristics of the stone. An example of an often overlooked but critical feature is "disturbed bedding," which, prior to the existence of the Corebook, would often not be reported. "If there's disturbed bedding at a site, even if there's a nice coal seam under it, it's likely that the (underground) mine's roof is going to collapse," Thompson says. "Either you can't mine there or you have to surface mine it." Conversely, at another site, a driller might have failed to find coal and filed a discouraging report, overlooking a bedrock characteristic described in the Corebook as "rooted."

"Coals form when you have a swamp, and the vegetation falls down and accumulates as peat. The roots go down into the soil underneath and those are preserved in the rock," Keith explains. "Sometimes the coal gets removed locally (by a storm, erosion, or other natural condition) before the overlying rocks were deposited on it, so you don't get any coal. But the fossil remains of the roots are preserved. This tells you that the coal may be present nearby."

Little standardization existed in exploration before the IGS team set out to create the Corebook. One scientist, John Ferm, created a numerical system years ago that is widely used in some areas, but it was difficult for a driller or geologist to remember which rocks went with which code numbers. Under the Corebook system, Ferm's rock 547 is now called Ssmr (sandstone, massive, rooted); this coding is more intuitive, with letters for the type of rock followed by letters for adjectives that clarify its specific characteristics.

In addition to its codes and charts, which correlate rock types with Ferm's system and narrative descriptions, the Corebook includes 73 full-color photographs of core and coal samples from the Illinois basin (southern Indiana, much of Illinois, and northern and western Kentucky). The samples were selected for the book as most representative of sedimentary rocks from the Pennsylvanian age (the dominant coal-producing era about 300 million years ago).

The technical aspects of producing the Corebook proved challenging. The photographs had to have perfect color resolution, and the book had to be rugged. Readers can rearrange the pages, which are bound in a looseleaf notebook, add modules, and remove pages. The paper itself is waterproof and almost impossible to tear. "This stuff is almost indestructible," Thompson says, inviting an onlooker to attempt to rip it. "It's like trying to open a package of crackers these days. You just can't do it!" In the field, Thompson explains, "we get dirty. But you can come back to the lab and spray this book with a hose. We also set it up so that one half of each page is for the drillers and the other for the geologists; that way the user can cut the book in half, so that if you only use one half, it fits in your back pocket."

To increase use of the book, which was published in 1996, the Geological Survey is conducting a series of workshops for drillers, other geologists, state mining and reclamation officials, and students. The workshop participants practice identification of actual core samples. Each workshop requires the five Survey geologists as instructors and 1,200 pounds of rock, transported to the teaching site. The workshops have been extremely popular.

"There are two kinds of people at these workshops," Thompson says. "We call them 'lumpers' and 'splitters.' Splitters say, 'There's a stack of thirteen blocks, each of equal size.' Lumpers say, 'There's a concrete block wall.'" In the workshops, lumpers will describe several feet of similar looking core as one rock type, while splitters will name each increment of the same core segment that looks slightly different as a different rock type. "Neither one is right or wrong," Keith adds. "We want them to understand the implications of whether you're a lumper or a splitter. Everything depends on how much information you want or need to know in a given sample, and that depends on the overall purpose of why the core hole is being drilled in the first place."

Beyond the concept of a flexible book and hands-on workshops, the Geological Survey staff now offers a computer program that further streamlines the often tedious field and laboratory work of describing samples. Called "Stratigraphic Column Generator," Thompson's program enables a field geologist or driller to type only the depth of the sample and the letter codes matching the Corebook into a notebook computer. With that information, the program generates a visual column at any selected scale to match the sample. In the office, researchers can compile the information as a database with other applications, such as the Geographic Information System (see p. 28) being developed by colleagues at the Survey.

The workshops, Corebook, (available through IGS for $85), and the Column Generator program form an accessible set of new tools that can dramatically en hance the work of field geologists, company analysts, and students. "It would have been amazing to have had all this in my geology classes," Thompson says.--Michael Wilkerson





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