News from the Indiana Geological and Water Survey
February 2023

Core to map: Scouting for outcrops

Editor’s note: The E-Geo News has been walking readers through the various steps required to turn physical data such as core samples into a functional geologic map. This is the fourth installment in this series; core collection was covered in September, core describing in November, and lab analysis in December.

It’s a warmish, sunny, January Tuesday, and Research Geologist Isaac Allred is on a working lunch. His office: The tucked-away trails of Hemlock Cliffs nature preserve in Crawford County. His objective: finding the point in this bedrock valley where two distinct ages of rock converge.

IGWS geologist Isaac Allred explores the contact between the Stephensport and Buffalo Wallow groups under a waterfall at Hemlock Cliffs in Crawford County. | Sara Clifford, IGWS

Rock hammer in hand, he finds what he’s looking for less than a mile in, clambering up and under a waterfall in a shallow canyon and recording the “meeting” with a photo. Tar Springs Formation sandstone above us, Glen Dean Limestone below us, this a group contact, a data point important to structural engineers, natural resource seekers (building stone; aggregates like gravel and sand; oil and gas; and water), zoning directors, and others.

On the other end of the trail, Valerie Beckham-Feller and Don Tripp work their way up from underneath another sun-dappled waterfall with a pole and a sighting device, measuring how many “Dons” it takes to get from the base of the Tick Ridge Sandstone Member of the Tar Springs Formation to its contact with the Glen Dean Limestone. (Answer: 14 Dons, or about 71.4 feet of layer thickness.) Thicknesses of formations—of sandstone, shale, and limestone—within rock unit groups are other major data points plotted on bedrock maps.

IGWS researchers Don Trip and Valerie Beckham-Feller measure the thickness of the Tick Ridge Sandstone Member at Hemlock Cliffs in Crawford County. | Sara Clifford, IGWS

When making a map, IGWS geologists not only gather new subsurface data through core drilling; they also pore through legacy data gathered over the past 100-plus years by other Survey geologists, as well as by oil and gas exploration companies. This area of the state—the Jasper quad—has been of limited commercial interest, so the team working on a new map through the U.S. Geological Survey’s STATEMAP program has primarily been verifying and adding to data collected by their predecessors—Clyde Malott, Henry Gray, and others—between the 1920s and ‘50s.

The Jasper team plotted places they wanted to visit on a digital map—some to verify data collected with less precise methods, some to gather new data in areas where the stratigraphy had been projected rather than measured. When some of this legacy data was collected, field geologists used a clinometer (an instrument to measure slope), a barometer, and a known altitude, like at a county courthouse, to plot locations and extrapolate thicknesses. In Crawford County, Tripp opened an app—which auto-locates him on GPS if he’s in service—entered notes about the elevation; the rock unit (group, formation, and member); anything notable he saw in samples, like fossils; and synced the program when he got back to the office. All that information then flows into a database that feeds the mapping software.

Of course, he takes paper notes, too, drawing diagrams of outcrops and noting details such as grain size, color, texture, thickness, and rock type. Even rocks within the same stratigraphic unit can vary from place to place because of changes they may have undergone after they were deposited, like the chemical qualities of the local groundwater that soaked into them over millions of years. Because of this, the Salem Limestone, for instance, could look different in Lawrence County than it does in Harrison County. Field visits help to inform and constrain these ranges of physical attributes.

“Engineers hate us because we’re not exact, but that’s just the nature of the game,” Tripp said.

Being attuned to the details of nature—from canyons and cliffs to sand grains and shells—is part of it, too. While vehicles whizzed by them on a highway shoulder, Allred, Beckham-Feller, and Tripp took turns with hand lenses and samples they’d chipped from a roadcut, searching for “forams” (foraminifera), gastropods, and other tiny fossils that give clues as to the rock’s age and stratigraphic placement.

“That’s, I think, the beauty of geology, is this lifetime search for answers about the Earth,” Allred said. “It’s like putting together a 1,000-piece puzzle. But every single piece can be valuable. … And we continually leverage technology and tools so we can frame this image in better detail.”

Glacial history of the Flatwoods revisited

A new paper published in late January in the Indiana Journal of Earth Sciences builds on research first published more than a century ago about the glaciation of the southern Midwest.

“Quaternary Stratigraphy and Geomorphic History of the Flatwoods Region of Owen and Monroe Counties, Indiana,” by Peter Jacobs, Henry Gray, Henry Loope, Jose Luis Antinao, and Robin Rupp, compiles generations of field observations and sampling, starting in the late 1800s with a survey by IU professor John Collett. The area was sweepingly revisited by IU professor Clyde Malott when he was an IU graduate student in “The Flatwoods Region of Owen and Monroe Counties in Indiana,” published in 1915. That paper was rereleased and annotated by IGWS geologist Gray in 1979; then-doctoral student Jacobs revisited the area in 1994 with a focus on soils; and IGWS researchers Loope, Antinao, and Rupp added new lab and field data to the collection over the past five years.

At least 70 core or outcrop sites and more than 20,000 data points were used to develop the stratigraphy and chronology and to reconstruct the topography of this bedrock valley that was buried during glaciation.

“While much has been learned about the Flatwoods region over the past 145 years, many questions still remain,” the authors wrote. “Most important is determining the age of the glacial sediments and how glaciation of the Flatwoods fits within the geologic framework of Indiana and North America.” Luminescence dating, which IGWS researchers can now do in-house, provided new data to address those questions. A deep test hole southeast of Spencer provided a 175-foot record from the surface to the base of the buried bedrock valley—other data that had been missing from the collection.

“While sediment records indicate an early glacier did impact the Flatwoods region,” the authors concluded, “and the loess and soil stratigraphy is more complete and complicated than Malott envisioned, we note that more than 100 years ago, Malott was essentially correct in his assessment that the sediment fill and geomorphology in the Flatwoods region is largely related to a single glaciation—a glaciation now numerically dated to the Illinois Episode.”

Read the research at this link.

Figures showing location of the Flatwoods study areas.

New StoryMap published

Between the 16th and 19th centuries, “cabinet” was a common term for a room of natural history, religious, or artistic collections. Filled with objects collected during expeditions or trading voyages, these "cabinets of curiosity" were the precursor to museums in Europe and the United States. A new, interactive StoryMap published in the Indiana Journal of Earth Sciences walks readers through the Indiana Geological and Water Survey’s own “cabinet of curiosity”: The Learning Lab.

IGWS Collections Intern Amanda Wollenweber, who’s worked in the Learning Lab for the past year, created this digital publication as her capstone project while completing a master’s degree in museum curatorship. She hopes the StoryMap will enable people in a wider radius from Bloomington to be able to enjoy and explore all the geologic objects the Learning Lab holds.

“When (IGWS Education and Outreach Coordinator) Polly (Sturgeon) did that preconstruction survey in 2019, 60 percent of people indicated they would only travel 50 miles or less to visit museums,” Wollenweber said. “We're hoping it (the StoryMap) will be an exhibit people can view if they cannot visit physically, or something to read that introduces the space or gives visitors extra information if they want to know more about the space.”

The StoryMap also provides a great introduction to geologic concepts like how depositional environment, glaciation, and other earth processes are reflected in sedimentary rock features; how fossils form; how chemical composition affects the crystal shape of minerals; and how scientists use the fossil record to study extinctions and climate changes.

View the StoryMap at this link.

2022 by the numbers

The Indiana Geological and Water Survey is a research institute, but it's also a public service institute. Education, through the collection of geologic specimens and data and the dissemination of scientific information, is a central part of our mission. Here's a snapshot of how we carried out that mission over the past year:

Staff and outreach news

• The Indiana Board of Licensure for Professional Geologists, chaired by IGWS Director Todd Thompson (pictured at right signing licenses), had its semiannual meeting Jan. 19 in Indianapolis. The board approved 11 applicants for professional licensing. Members also discussed the development of continuing education rules that were mandated by Public Law 108-2022; more information will be shared as it becomes available.

• IGWS researcher Valerie Beckham-Feller was elected treasurer of the Eastern Section of the American Association of Petroleum Geologists (AAPG) late last year. This is a progressive office term whereby she’ll serve as treasurer in year 1 (fall 2022-fall 2023), secretary in year 2, vice president in year 3, and president in year 4.

• IGWS researchers Ginger Davis and Jose Luis Antinao spoke to well drillers attending a continuing education workshop in Columbus on Jan. 10. Davis’s topic was “Indiana Geology: Descriptions, library, and resources available”; Antinao’s topic was “Geological Processes Relevant to Groundwater Investigations in Indiana.” Davis, along with IGWS researcher McKailey Sabaj, repeated the “Indiana Geology” talk at another well drillers’ workshop in Brownsburg Jan. 17.

• University Collections featured an American mastodon mandible from the IGWS Learning Lab for its Object of the Month in January.

• The IGWS’s range of research is displayed on two large panels hanging in Indiana Statehouse tunnels through the end of March (one example below).

Contact us

The Indiana Geological and Water Survey, a longstanding institute of Indiana University, conducts research; surveys the state; collects and preserves geologic specimens and data; and disseminates information to contribute to the mitigation of geologic hazards and the wise stewardship of the energy, mineral, and water resources of Indiana.

• To join the monthly E-Geo News mailing list, please click here.

• To ask a question of IGWS staff or suggest an E-Geo News topic, email scliffo@iu.edu.