Characterization of organic matter in the Yegua formation (Brazos County, Texas) : relation to microbial processes and depositional environment /
in sediments, and VOAS and neutral sugars were analyzed in groundwaters to characterize sedimentary and dissolved organic carbon (DOC). Geochemical and microbiological evidence indicate viable microorganisms which produce or consume VOAs. Acetic and propionic acids in mudstones range from 200 - 1270...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733039611&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | in sediments, and VOAS and neutral sugars were analyzed in groundwaters to characterize sedimentary and dissolved organic carbon (DOC). Geochemical and microbiological evidence indicate viable microorganisms which produce or consume VOAs. Acetic and propionic acids in mudstones range from 200 - 1270 and 20 - 38 []. In contrast, acetic and propionic acids in sands are 50 - 200 and < 20 [] VOA analyses and laboratory incubations suggest production of VOAs in mudstones, and consumption of VOAs by sulfate reducing bacteria (SRB) in sands. Assuming that SRB completely respire the acetate transported into the aquifer (5.4 [], the [] production rate is 9.2 []. This value is within the range for deep aquifers, but 103 to 105 times slower than near-surface microbial processes. This slow mineralization of organic matter (OM) and a loose commensalism between the microbial communities probably accounts for their long-term survival. Sedimentological and geochemical evidence indicate depositional cycles represented as parasequences separated by exposure surfaces. Organic petrography and geochemistry indicate presence of terrestrial and marine OM in transgressive sediments. In contrast, regressive sediments contain only terrestrial OM. These differences relate to contrasting OM sources and depositional styles on the shelf . The study suggests that organic geochemistry data combined with sedimentology provide greater resolution in distinguishing stratigraphic boundaries. High, intermediate, and low molecular weight (HMW,IMW, and LMW) DOC, VOAs, and neutral sugars were analyzed. DOC ranges from 1 - 6 [], with 1MW and HMW DOC as major fractions. VOAs comprise 3 - 20% and neutral sugars 0.8 - 6.7% of DOC. Acetic acid ranges from 1.0 - 4.1 [] in shallow versus 0.37 - 0.52 [] in deeper groundwaters. Neutral sugars range in concentration from 0.6 to 2.7 []. Neutral sugars in shallow groundwaters are more diagnostically altered as indicated by high moles fucose+rhamnose and low neutral sugar yield. Bulk [] of DOC and HMW DOC ranges from -24 to -32%., and LMW DOC ranges from -32 to -34%c. In contrast, soil-zone OM [] is higher (-16 to -19%4. Moreover, the carbon isotopes imply a predominantly [] source for DOC. |
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| Item Description: | Vita. "Major Subject: Geology". |
| Physical Description: | xii, 95 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 85-94). |