Distinguishing storm or fire events in historic sediments
description
Transcript of Distinguishing storm or fire events in historic sediments
![Page 1: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/1.jpg)
Distinguishing storm or fire events in historic sediments Willy Amidon, Eric Butler
![Page 2: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/2.jpg)
Introduction
• Lake sediments record past events
• Coring allows study of these records
Previous work
Brown (2000), Noren (2001) used long (6m) cores to reconstruct paleoclimate and environment
- identified coarse, inorganic sediment layers
- interpreted as storm events
OUR PURPOSE: Distinguish fire events from storm events
![Page 3: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/3.jpg)
Goals
Use short cores (< 40cm) to:
• Quantify historic charcoal levels
• Identify historic/prehistoric boundary
• Interpret any “storm” layers found
• Refine lab techniques
![Page 4: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/4.jpg)
Methods of analysis
• Visual logs
- Changes in color, density, grain size, debris
• Loss on Ignition (LOI)
- Identifies trends in organic carbon content
• Charcoal analysis
- Elemental analyzer quantifies elemental carbon (charcoal)
![Page 5: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/5.jpg)
![Page 6: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/6.jpg)
Coring method
• Gravity cores from canoe
• Extrude in the field
• Cores separated into 1 cm intervals
![Page 7: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/7.jpg)
Sample preparation
• Dry samples & weigh
• Digest in nitric acid
- removes organic carbon
• Rinse & dry, weigh
• Elemental analyzer
- measures elemental carbon (charcoal)
![Page 8: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/8.jpg)
Results
• Incomplete digestion (SY)
• Incomplete washing (SY, OG)
![Page 9: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/9.jpg)
Alternate methods
• Visual log on OG core
• LOI on OG core
Results
• Correlation between LOI and organic material
• Suggests a storm/fire layer?
• May also represent logging
10 12 14 16 18 20
30
25
20
15
10
5
Loss-on-ignition (%)
![Page 10: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/10.jpg)
Coming soon
• Elemental analysis on rewashed samples
- % charcoal content
• Hopeful correlation with LOI and visual log
- Does increase in charcoal correlate with decrease in LOI & color change?
![Page 11: Distinguishing storm or fire events in historic sediments](https://reader036.fdocuments.net/reader036/viewer/2022083006/56813d11550346895da6cd04/html5/thumbnails/11.jpg)
Future work
• Apply procedure to longer cores
• Pb210 dating of macrofossils (wood chips)
• Analyze & compare more short cores