Masters Theses
Date of Award
12-1988
Degree Type
Thesis
Degree Name
Master of Science
Major
Geology
Major Professor
Paul A. Delcourt
Committee Members
Hazel Delcourt, Stephen Driese, Thomas Broadhead
Abstract
The palynological and sedimentological records preserved in sediment of the Powers Fort Swale, Butler County, Missouri provide the first full-glacial record of vegetational change and the first radiocarbon chronology of late- Quaternary fluvial events in the Western Lowlands physiographic region, Lower Mississippi River Valley. From 18,000 to 14,500 years Before Present (yr B.P.) spruce (Piced) dominated the Lowland forests. About 16,300 yr B.P., the braided Mississippi River shifted most of its flow of glacial meltwater out of the Western Lowlands and eastward into the St. Francis Basin. The remainder of Mississippi River flow maintained a more restricted valley train of braided streams in the Western Lowlands. At about 14,500 yr B.P., late-glacial climatic amelioration and decrease in meltwater influx resulted in the replacement of boreal spruce populations by cool-temperate deciduous taxa dominated by oak (Quercus). Infrequent late-glacial flow of glacial meltwater continued until as late as 11,600 yr B.P. after which the Western Lowlands were shaped by meandering streams with headwaters in the eastern Ozark Plateau.
At 9,500 yr B.P., Holocene vegetation changed from cool-temperate to warm-temperate forests dominated by oak, and was similar in tree composition to the modern bottomland forests of the Western Lowlands. Increase in warm and dry climatic conditions representing the Hypsithermal Interval occurred during the middle Holocene, producing decreases in groundwater level, flood frequency and size of meandering streams, and consequently reduction in the aerial extent of bottomland swamp within Powers Fort Swale. During the middle Holocene, mesic tree taxa were replaced by more xeric oaks and hickories (Carya spp.), and populations of baldcypress (Taxodium distichum) were progressively restricted to the inundated portions of the swale.
With the late-Holocene increase in regional precipitation and consequent rise in groundwater level at 4,500 yr B.P., xeric-adapted oaks and hickories were replaced by mesic taxa such as elm (Ulmus), and baldcypress expanded with the standing-water margin to form a closed-canopy forest over the swale. Increase in both flood frequency and magnitude of nearby meandering streams produced disturbed alluvial environment inhabited by abundant willow (Salix) trees. Around 600 yr B.P., Powers Phase Indians occupied uplands at the margin of Powers Fort Swale and cultivated corn producing a prehistoric ragweed (Ambrosia type) rise and the first occurrence of corn (Zea mays) in the fossilpollen record.
Recommended Citation
Royall, P. Daniel, "Late-Quaternary paleoecology and paleoenvironments of the Western Lowlands, southeast Missouri. " Master's Thesis, University of Tennessee, 1988.
https://trace.tennessee.edu/utk_gradthes/13327
