Abstract
Speleothem based timing for prairie incursion in southeastern Minnesota and northeastern Iowa and its implication on temperature vs. changes in E-T balance during the mid-Holocene
Abstracts with programs - Geological Society of America, Vol.30(7), p.114
Geological Society of America, 1998 annual meeting
1998
Abstract
The carbon isotopic record for speleothems from Spring Valley Caverns in southeastern Minnesota indicates that prairie arrived in this region at approximately 7800 YBP. In contrast, the carbon isotopic record in speleothems from Cold Water Cave in northeastern Iowa, 40 km (25 mi.) southeast of Spring Valley, indicates that prairie arrived in this area at approximately 5900 YBP. The data indicates that the arrival of prairie in northeastern Iowa was delayed by over 2000 years relative to southeastern Minnesota. However, the change from prairie to savanna is initiated in both sites at approximately 3400 to 3500 YBP and complete by 2100 to 2200 YBP. The oxygen isotopic record for the Spring Valley speleothems shows a major (nearly 2 per mil) increase that is similar in timing (approximately 100 years later) to that of the carbon isotopic record. The oxygen isotopic record for Cold Water Cave speleothems is highly variable with one speleothem exhibiting a major increase in 18-O and two others remaining unaffected or even showing a small decrease during the middle Holocene. Though an increase of nearly 2 per mil in the oxygen isotopic record for a single speleothem in Cold Water Cave had been previously interpreted to reflect mostly a temperature change, the long lived difference between Cold Water Cave and Spring Valley Caverns speleothems suggests that the observed 2 per mil 18-O enrichments are a result of pre-infiltration evaporative effects on the isotopic composition of vadose water and not the result of a temperature increase. Though a minor (1 degrees C) temperature increase might have accompanied the mid-Holocene vegetation change, it is masked by major changes in E-T balance that affect the isotopic composition of vadose fluids. The increased evaporation is a consequences of the rapid removal of tree cover (canopy) over the caves that buffered evaporative effects, coupled with changes in seasonality of precipitation.
Details
- Title: Subtitle
- Speleothem based timing for prairie incursion in southeastern Minnesota and northeastern Iowa and its implication on temperature vs. changes in E-T balance during the mid-Holocene
- Creators
- Luis A Gonzalez - University of Iowa, Department of Geology Iowa City, IA USA United StatesRhawn F DennistonRichard G BakerMark K Reagan
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.30(7), p.114
- Conference
- Geological Society of America, 1998 annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 1998 annual meeting
- Language
- English
- Date published
- 1998
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240803802771
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