Geology topics

Research about eastern Tennessee

Source-linked reports with geographic coverage including eastern Tennessee.

3 recordsLinked to original sources

USGS2024

Limited evidence of late Quaternary tectonic surface deformation in the eastern Tennessee seismic zone, USA

The ~300-km-long eastern Tennessee seismic zone (ETSZ), USA, is the second-most seismically active region east of the Rocky Mountains. Seismicity generally occurs below the Paleozoic fold-and-thrust belt within the Mesoproterozoic basement, at depths of 5–26 km, and earthquake magnitudes during the instrumental record have been moment magnitude ( M w )≤4.8. Evidence of surface deformation may not exist or be difficult to detect because of the vegetated and soil-mantled landscape, landslides, locally steep topography, anthropogenic landscape modification, or long, irregular recurrence intervals between surface-rupturing earthquakes. Despite the deep seismicity, analog models indicate that accumulation of strike-slip or oblique-slip displacement at depth could be expected to propagate upward through the Paleozoic section, producing a detectable surficial signal of distributed faulting. To identify potential surface deformation, we interrogated the landscape at different spatial scales. We evaluated morphotectonic and channel metrics, such as channel sinuosity and catchment-scale hypsometry. Additionally, we mapped possible fault-related topographic features on 1-m lidar. Finally, we integrated our observations with available bedrock and Quaternary surficial mapping and subsurface geophysical data. At a regional scale, most morphotectonic and channel metrics have a strong lithologic control. Within smaller regions of similar lithology, we observe changes in landscape metrics like channel sinuosity and catchment-scale hypsometry that spatially correlate with new lineaments identified in this study and previously mapped east–west Cenozoic faults. These faults have apparent left-lateral offsets, are optimally oriented to slip in the current stress field, and match kinematics from recent focal mechanisms, but do not clearly preserve evidence of late Pleistocene or Holocene tectonic surface deformation. Most newly mapped lineaments might be explained by either tectonic or non-tectonic origins, such as fluvial or karst processes. We also re-evaluated a previously described paleoseismic site and interpret that the exposure does not record evidence of late Pleistocene faulting but instead is explained by fluvial stratigraphy.

Tennessee↗

USGS1986

Water-quality appraisal of NASQAN stations below impoundments, eastern Tennessee

The National Stream Quality Accounting Network (NASQAN) is a network of stations at which systematic and continuing water-quality data are collected. Major objectives of this U.S. Geological Survey program are (1) to depict areal variability of streamflow and water-quality conditions nationwide on a year-by-year basis and (2) to detect long-term changes in streamflow and stream quality. Several NASQAN stations in East Tennessee are downstream from impoundments which have a significant effect on water quality. NASQAN data obtained from the Tennessee River below Watts Bar Dam and the Clinch River below Melton Hill Dam were compared to water-quality data from the basins upstream. The comparison indicates that NASQAN data obtained below impoundment may not be adequate to describe a composite picture of water quality in the accounting unit. Detention time of storage in the impoundments is believed to moderate the range of constituent values observed at the NASQAN stations. Data obtained upstream and downstream from Watts Bar Dam indicate that the water sampled at the NASQAN station comes from stratified layers of the impoundment and is not representative of an integrated sample of water from the impoundment. Values of total recoverable iron suggest that, because of adsorption to sediments in impoundments, some constituents are not accurately described by sampling below impoundments. Relations between water-quality constituents and flow at stations on the Clinch River and Tennessee River are not well defined due to regulation. Direct load computations for many constituents were therefore not possible, which diminished the utility of data from these NASQAN stations to account for quantity versus quality of the water. Load computations were only possible for ionic constituents through use of a continuous specific-conductance record as an intermediary. Compensation for the effects of discharge prior to application of the Seasonal Kendall test for trends could not be done and identification of trends in water-quality constituents caused by some process (source) change was not possible. Some water-quality trends indicated by data from the Clinch and Tennessee Rivers might reflect the decreasing trend in discharge during the 1972-82 water years. Thus the stations below Watts Bar Dam and below Melton Hill Dam do not adequately meet the NASQAN objective to detect and assess long-term changes in stream quality.

Tennessee↗

USGS1986

Evaluation of coal-mining impacts using numerical classification of benthic invertebrate data from streams draining a heavily mined basin in eastern Tennessee

Coal-mining impacts on Smoky Creek, eastern Tennessee were evaluated using water quality and benthic invertebrate data. Data from mined sites were also compared with water quality and invertebrate fauna found at Crabapple Branch, an undisturbed stream in a nearby basin. Although differences in water quality constituent concentrations and physical habitat conditions at sampling sites were apparent, commonly used measures of benthic invertebrate sample data such as number of taxa, sample diversity, number of organisms, and biomass were inadequate for determining differences in stream environments. Clustering algorithms were more useful in determining differences in benthic invertebrate community structure and composition. Normal (collections) and inverse (species) analyses based on presence-absence data of species of Ephemeroptera, Plecoptera, and Tricoptera were compared using constancy, fidelity, and relative abundance of species found at stations with similar fauna. These analyses identified differences in benthic community composition due to seasonal variations in invertebrate life histories. When data from a single season were examined, sites on tributary streams generally clustered separately from sites on Smoky Creek. These analyses compared with differences in water quality, stream size, and substrate characteristics between tributary sites and the more degraded main stem sites, indicated that numerical classification of invertebrate data can provide discharge-independent information useful in rapid evaluations of in-stream environmental conditions.

Tennessee↗