People have been studying what exists beneath Illinois’ surface since the 1830s. This research exists as mountains of careful observations, combined with numerous individual research projects, distilled into three seminal scientific reports published decades ago on paper — crowning achievements of many a career at the Illinois State Geological Survey.
Now freed from the book shelf, the collected knowledge of Illinois’ geologic past has been digitized, and released online as ILSTRAT – an interactive resource for the public, industry, and government to understand the rocks beneath our feet. Organized as an editable online database, or wiki, ILSTRAT brings to life the best scientific consensus of how Illinois was built – from the ground down.
Did you know?
- In Illinois, we walk around on a relatively thin "skin" of unconsolidated sand, soils, silts, and glacial deposits that can range in thickness from a few feet to a few hundred feet.
- Illinois also has a “basement.” These are Precambrian rocks older than 542 million years, formed before complex multicellular lifeforms began to appear on Earth. They are found starting 1,500 feet deep in Jo Daviess County, but plummet continuously southward to the area around Shawnee National Forest where they are found 14,000 feet below the surface.
- Ever heard of Cook County? ILSTRAT tells us that under its ”skin” of glacial sediments, the bedrock is mostly 420 million- to 440 million-year-old dolomites composed of the remnants of ancient tropical reefs formed when Illinois was at the equator!
Geologists study rock layers to locate water and other valuable resources that form over millions of years. These collected studies also helped work out our understanding about how the Earth formed and was changed by climate and movements of the earth’s crust. More than 500 distinct geologic ‘units’ have been identified so far in Illinois.
Geologists have discovered a lot about Illinois in the 40 years since the publication of the reports used initially to build ILSTRAT. But without a major paper publication to gather them all together, those revisions and revelations remain scattered in presentations, papers, and notebooks of individual investigators. Many of these pending updates await capture in ILSTRAT by those same investigators, and going forward it will spur regular updates as a ready repository for new discoveries to advance the scientific picture. In effect, ILSTRAT provides both a baseline for understanding the stratigraphy of Illinois, and more importantly, a framework to update and build to the future.
“Geologists are constantly making new discoveries and refining our understanding of rock layers,” said ISGS Geologist Scott Elrick. Geologist Jennifer Obrad, who did much of the heavy lifting in editing ILSTRAT, offered two examples of major pending additions to the database. First is an extensive update of Pennsylvanian rocks (323 million to 299 million years ago) by John Nelson and others. The second is a compendium of fossils characteristic of the Platteville Dolomite (485 million to 444 million years ago) by Dennis Kolata.
ILSTRAT joins a group of other scientific resources at ISGS intended to burst the academic bubble by being accessible to the public. Visual (linked to Google maps), searchable, and mobile (phone accessible), these databases offer rich information for specialists, students, hikers, and hobbyists.
- Are you standing on top of a coal mine? Check ILMINES.
- Is there a water aquifer down below? ILWATER is the place to go.
- Where is the nearest oil or gas field? ILOIL has the answers.
The newcomer, ILSTRAT, represents an encyclopedic reference to provide a scientific touchstone for our geologic data. It also can flexibly accommodate multimedia material that can make data points more informative and accessible. For example, Google maps connectivity may be added to increase its ease of use for visualizing geographic extents of geologic units.
Because ILSTRAT is a living repository for the scientific community, industry, and the public, geologists at other colleges, other state geologic surveys and industry can propose updates of information, logs, and pictures. Even knowledgeable amateurs could help improve the database with their observations. For instance, the discovery of a fossil in an area between two units could help better refine a formation’s age, or the type of biota that once lived there.
The products of the latest geological technology — such as surface mapping with lasers, subsurface modeling with magnetism, and state-of-the-art 3D mapping — will all become important new pieces of data for ILSTRAT in describing and cataloging the hidden world beneath our feet.
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