Stratigraphic evidence of human-induced disturbance of Missouri Ozarks streams

Conference · Mon Mar 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5011341

Jacobson, R B; Pugh, A L; McKenney, R A ^[1]

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1. Geological Survey, Rolla, MO (United States)

Long-term residents of the Missouri Ozarks consistently report that small Ozarks streams (less than 4,000 square kilometers drainage area) have been filling with gravel during the last 60 to 80 years. As part of a multidisciplinary study to evaluate the origins and effects of gravel aggradation, the stratigraphic record of alluvial processes in Ozarks streams has been investigated to determine the nature and magnitude of sedimentologic changes preceding European settlement and post-dating subsequent land-use changes. Synthesis of data collected during previous studies and a regional reconnaissance-level stratigraphic study indicate that alluvium has been deposited episodically in Ozarks streams since the middle Holocene. Periods of deposition occurred around 7 ka BP (thousands of years before present), 4.6 to 4.0 ka BP, 2.2 to 1.6 ka BP, 1.1 to 0.9 ka BP, and during the last 100 years. In general, alluvial units dating from before 1.6 ka BP are characterized by fining-upward sequences of coarse gravel to silt-loam, inset laterally against one another. Episodic deposition of alluvium during the period 7.0 to 1.6 ka BP is indicative of the natural background rate of alluvial disturbance, presumably caused by persistent climatic anomalies. Distinct sedimentologic changes and increased charcoal content in deposits dating from 1.1 ka BP to 1800 A.D., are interpreted as evidence of an increased sediment supply, perhaps as a result of increased frequency of forest fire. The shift to deposition of mostly sand and gravel after 1800 A.D. indicates that a substantial disturbance of the hydrologic and sediment budgets, or both, of Ozarks streams accompanied land-use changes after European settlement.

• OSTI ID: 5011341
• Report Number(s): CONF-9303210--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:3
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540310 -- Environment
Aquatic-- Basic Studies-- (1990-)
58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ALLUVIAL DEPOSITS
DEPOSITION
DEVELOPED COUNTRIES
GEOLOGIC DEPOSITS
GEOLOGY
MISSOURI
NORTH AMERICA
STRATIGRAPHY
USA