Overview of Indiana Bedrock Geology 6 - Bedrock geology.pdf · Department of Geological Sciences | Indiana University (c) 2012, P. David Polly Paleontology and Geology of Indiana

Department of Geological Sciences | Indiana University(c) 2012, P. David Polly Paleontology and Geology of Indiana

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P. David PollyDepartment of Geological SciencesIndiana UniversityBloomington, Indiana 47405 [email protected]

Indiana bedrock geology

Overview of Indiana Bedrock Geology

mailto:[email protected]

mailto:[email protected]

Objectives


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1. Indiana’s bedrock geological map

2. Cross-section of bedrock geology in Indiana

3. Large and small scale geological maps

4. William Smith and the first geological map

5. Stratigraphic column of Indiana

6. Stratigraphic terminology

7. David Dale Owen and geology of the Mississippi Basin

8. Overview of events represented in Indiana’s rocks


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About geological maps

• Regions are color-coded by the age of the rocks

• Small scale maps (i.e., ones that cover large areas) are simplified by combining rock units into larger and larger age categories

• Bedrock geology consists of rock units that are lithified and extend below the surface (in most cases)

• Bedrock geology is distinguished from surficial geology, which consists of rock, dust, mud, sand, soils, and other lithic debris that has been left on the surface of the bedrock by rivers, streams, wind, glaciers, etc. Map of Indiana Showing Bedrock Geology. 1990.

Drafted by Kimberly Sowder. Indiana Geological Survey.


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Map of Indiana Showing Bedrock Geology. 1990. Drafted by Kimberly Sowder. Indiana Geological Survey.

Bedrock geological map


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Cross section (west to east) of Indiana’s major rock units

Map of Indiana Showing Bedrock Geology. 1990. Drafted by Kimberly Sowder. Indiana Geological Survey.


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Youngest (320 mya) Pennsylvanian

Oldest (360 mya) Earlier Mississippian

Edwardsville Fm. (Borden River Delta)

Salem Limestone and others (Shallow tropical seas)

Limestones Sandstones, Shales, and Coals (Nearshore seas and Terrestrial Swamps)

Bedrock Geology of Indiana. 2002. H. H. Gray (data compiler). Indiana Geological Survey.

Bedrock geology of Monroe County


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Canal lock in Essex, England

William Smith monument in

Churchill, England

British canals

Wm. Smith (1769-1839)

William Smith and the first geological map


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William Smith’s 1815 Geological Map

William Smith’s Observations

• Different types of rock were not distributed randomly

• Different types of rock could be mapped as units

• If a rock unit lay on top of another in one area, it did in other areas as well

• Sedimentary rock units each had unique fossils that were not found in other units


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19th Century canals in North America


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Indiana Geological Survey

Stratigraphic columns are the “keys” to geological maps


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TerminologyChronostratigraphic units – units of time. Periods in the basic geological timescale are chronostratigraphic units, as are units measured in millions of years ago. From large to small these units are called eons, eras, periods, epochs, and ages. For example, “the first land plants evolved during the Silurian Period”. This sentence makes no reference to any particular rocks, only to a time in the Earth’s past.

Time-stratigraphic units – units of rock that belong to a certain time period. Groupings of rock layers based on their geological age are time-stratigraphic units. From larger to smaller these units are called systems, series, and stages. Temporal groups of rocks usually have a corresponding time unit with the same name. For example, “The Silurian System in Indiana was formed during the Siluran Era”.

Lithological units – mappable units of rocks that have similar age and the same general lithology. Groupings of rock layers as you see them in the ground. Usually rocks that are grouped together this way formed in the same environment (such as the delta of a particular ancient river). Formations are the basic lithological unit. Formations are divided into members and beds, and grouped into groups. Example, “The Borden Group contains the Edwardsville Formation and is Mississippian in age”.


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Stratigraphy in Indiana

David Dale Owen (1807-1860)

• Stratigrapher and geologist, Dale Owen was a son of Robert Owen, the socialist utopian who founded New Harmony, Indiana.

• Dale Owen conducted the first geological survey of Indiana, Kentucky, Arkansas, Iowa, Minnesota and Wisconsin

• In 1860, Owen’s museum in New Harmony was the largest west of the Appalachians.

New Harmony

Ground sloth skeleton from Owen’s Museum, shown here in it’s later home at Indiana University


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Ordovician

Silurian

Devonian

Mississippian

Pennsylvanian

Youngest (300 mya)

Oldest (470 mya)

Bedrock Geology of Indiana. 2002. H. H. Gray (data compiler). Indiana Geological Survey.

Bedrock Geology Overview

Early fishes

First land plants

First land animals

Coal swamps


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Glacial Till

Surficial and Bedrock Geology of Indiana. 2002. H. H. Gray (data compiler). Indiana Geological Survey.

Quaternary geology

The Quaternary

Mammal-like Reptiles

Early dinosaurs

Late dinosaurs

Early mammals

Late mammals

Documents

Overview of Indiana Bedrock Geology 6 - Bedrock geology.pdf · Department of Geological Sciences | Indiana University (c) 2012, P. David Polly Paleontology and Geology of Indiana