Department of Geology and Geography
|Paleoecology of southwestern Louisiana:|
|...||My Ph.D. dissertation at Louisiana State
University was a paleoecological study of southwestern Louisiana. Travelers
on Interstate 10 between Lafayette and Lake Charles pass through a region
of rice fields which was originally a natural tall grass prairie. I like
grasslands, and the idea of looking for changes in the southern prairie-forest
ecotone appealed to me. Under Dr. Kam-biu Liu's direction, I started my
study using pollen, went to the University of
Minnesota to learn phytoliths in order to refine
the pollen data, and eventually included diatoms
because they were in my phytolith samples. My dissertation research was
supported primarily by the National Science Foundation, the Association
of American Geographers, and the Robert West Fund of the LSU Geography
and Anthropology Department.
|The Southwestern Louisiana Prairie|
|Publications on southwestern Louisiana include:|
|Fearn, M.L. 1995. Louisiana's Cajun Prairie: Holocene History of a Southern Grassland. Ph.D. dissertation. Louisiana State University, Baton Rouge, Louisiana.|
Pollen, phytoliths, and charcoal suggest that the grassland island has neither expanded nor contracted over the last 6000 years and that fire has contributed to its maintenance. Pinus, Quercus, and Taxodium have been components of southwestern Louisiana's vegetation for the entire period of record with a minor increase in pine from 2000 to 1000 B.P.
High pollen concentrations followed by an Ambrosia rise and a drop in Taxodium and Pinus mark the settlement horizon. Low pollen influx after settlement indicates high rates of erosion and clastic input to the lakes. A crash in the diatom flora of Lake Arthur probably relates to maximum pollution of the estuary by agricultural chemicals.
The use of phytoliths in sediment to distinguish the source of Gramineae pollen is a promising new technique. Dramatic increases in Gramineae pollen accompanied by high percentages of rondel shaped phytoliths document expanding marsh vegetation around Lake Arthur and Prien Lake as rising sea level initiated drowning of the low gradient rivers by 5000 B.P.
Radiocarbon dates on peat samples indicate relative sea
level of -5.5 m by 6000 B.P. followed by slow steady rise at a rate of
9 cm/100 years up to present times. Freshwater diatom assemblages between
4500 and 3000 B.P. coincide with westward progradation of the Mississippi
River's Teche Delta Complex, and an abrupt shift to brackish/marine diatom
flora at 3000 B.P. signals abandonment of the Teche system.
|Fearn, M.L. 1998. Phytoliths in sediment as indicators of grass pollen source. Review of Palaeobotany and Palynology 103: 75-81.|
Keywords: Phytoliths, pollen, grasslands, marshes, Louisiana
|Fearn, M.L. In review. Holocene history of Louisiana’s tallgrass prairie outlier.|
|See also: Presentations
with Published Abstracts
|Mimi Fearn Home
University of South Alabama
Last modified: 5/26/99