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Geology and geography section. (Abstracts of Papers Presented at the 111th Meeting).

IMPLICATIONS OF CARBON AND OXYGEN ISOTOPIC RATIOS IN PALEOZOIC CHERT AND HOST CARBONATE ROCKS IN THE VICINITY OF CHATTANOOGA, TENNESSEE. Habte Giorgis Churnet, The University of Tennessee, Chattanooga, Chattanooga, Tennessee. Variation of Carbon isotopic ratios in carbonate deposits of the Chattanooga area is consistent with secular variation reported in the literature for the Paleozoic of other regions. Heavy oxygen isotope enrichment in Paleozoic chert nodules of the Chattanooga area is much lower than that determined in Cenozoic chert bearing carbonates elsewhere. In fact, the Mississippian carbonate host rock is slightly more enriched than the chert in the Fort Payne Formation, and likely indicates disequilibrium conditions and/or contamination of the silicifying fluid. Oxygen isotopic ratios in Middle Ordovician and Mississippian carbonates are within the range of secular variations in temperature reported in the literature for these age rocks. However, Oxygen isotopic ratios in Cambrian to Ordovician Kn ox Group chert nodules and in the host carbonates are quite low. Three possible explanations include: (1) the [delta] [O.sup.18] values of the diagenetic solutions or the Cambrian Ocean are very low, (2) the Oxygen isotopic ratios are not well preserved, or (3) the diagenetic solutions are of a higher temperature. Presence of breakthrough breccia in Chattanooga similar in setting to telethermal Mississippi Valley Type deposits elsewhere in the Knox Group is indicative of involvement of fluids of higher temperatures. Calculations yield temperatures up to 53[degrees]C (on ice free basis) for Knox Group at Chattanooga, which would have been too hot for an ocean in which brachiopods survived. It is more likely that warmer fluids diagenetically altered the Knox Group carbonate rocks. Likewise, silicification not only in the Knox Group but also in the Middle Ordovician carbonates (48-58[degrees]C) was from warm fluids. Silicification of the Mississippian Fort Payne is at a higher temperature (41[degrees]C) than the host carbonate diagenetic temperature of 13[degrees]C (on modern [delta] [O.sup.18.sub.w]) basis. It appears that the chertification temperatures are least estimates of the diagenetic fluid temperatures owing to contamination by the oxygen ratio of the protolith. These tentative interpretations are based on a minimum of one sample from each deposit mentioned above.

THE MALONE COLLECTION. Malcolm T. Sadler and James X. Corgan, Austin Peay State University, Clarksville Tennessee. Every day scores of visitors to the Clarksville Public Library walk past a display of 700 marine organisms. In the display, labels discuss the classification, variability, and ecology of marine life, while some labels identify books and Internet resources that aid in interpreting animals and plants. Clarksville's Customs House Museum has 1900 additional identified specimens in storage. These specimens will be used in exhibits such as "The Rocky Shore" and in kits that stress identification skills. Kits will serve youth groups and senior citizens. Dr. F. J. Malone and his family, creators of The Malone Collection, were at a United States Navy facility on Andros Island, Bahamas in 1974. Collecting natural history specimens became a hobby, but specimens were never identified. Every town has collectors of butterflies, minerals, etc. These items can be lost when a collector dies. Yet science teachers can curate collections. In this case, personal treasures are becoming a community resource.

PROVENANCE OF THE PEORIA LOESS IN THE NORTHERN MISSISSIPPI EMBAYMENT. David N. Lumsden, Joseph W. Galluzzi, Patrick A. Drouin, and Charles H. Lumsden, The University of Memphis, Memphis, Tennessee. The Peoria Loess caps two regionally prominent topographic highs in the Northern Mississippi Embayment (NME), Crowley's Ridge, Arkansas and the Chickasaw Bluffs, Tennessee. Changes that took place in the pathway of the Mississippi-Missouri-Ohio river system in the NME during Late Wisconsinan suggest that the proximal source of wind-deflated silt for the Peoria varied substantially in the interval of its deposition (circa 22,000 to 10,000 years BP). The basic question we asked is: "Can XRD of bulk samples be used to define mineralogical variations within the Peoria Loess, thereby providing a basis for interpretation of its provenance and depositional history?" We focused on feldspar and dolomite mineralogy in samples from five exposures along Crowley's Ridge and five along the Chickasaw Bluffs. Samples from Minnesot a, Illinois, and Iowa provided insight into source area compositions. The Peoria Loess in the NME contains an average of 5--7% Nafeldspar ([d.sup.002] = 3.18--3.20A) and 2-4% K-feldspar ([d.sub.220] = 3.23 --3.25A). The feldspar proportion varies randomly from location to location and is essentially similar on both features. Below the modern soil dolomite varies from 6--13% at seven locations, is absent at two locations and is present in the two basal samples at one other. The silt-sized dolomite grains have a similar nearstoichiometric composition and abraded appearance, wherever present. Neither feldspar nor dolomite abundance varies systematically with depth, except for the absence of dolomite in the modern soil. The similarity in abundance and composition of feldspar and dolomite in the Peoria Loess of both Crowley's Ridge and the Chickasaw Bluffs makes mineral-based subdivision difficult. The uniform abundance of dolomite below the modern soil suggests that soils did not have a chance to form during Peor ia deposition.

* Student author.
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Author:Lumsden, David
Publication:Journal of the Tennessee Academy of Science
Article Type:Brief Article
Geographic Code:1USA
Date:Jan 1, 2002
Words:857
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