Stratigraphy of the quaternary terraces of the Brazos River in the Texas A&M University-Riverside Campus Area, Brazos County, Texas /
Brazos County, Texas, four terraces of the Brazos River have been mapped. The lithostratigraphic and soils geomorphic study of the deposits forming the second higher terrace shows that this terrace complex is basically comprised of three different alloformations, and it has been designated as the (R...
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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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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733039221&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Brazos County, Texas, four terraces of the Brazos River have been mapped. The lithostratigraphic and soils geomorphic study of the deposits forming the second higher terrace shows that this terrace complex is basically comprised of three different alloformations, and it has been designated as the (Riverside Terrace Complex' in this study. The oldest, alloformation-3, is seen to underlie both the (Riverside Terrace' and the fourth terrace mapped to the east of the campus, and is comprised of two distinct channel depositional sequences. It is believed that the formation of this alloformation may have involved multiple cut and fill episodes that occurred prior to the Wisconsinan period. The formation of alloformation-2 involved several degradation-aggradation cycles occurring in response to the intermediate type glacial and intersticial climatic and sea-level conditions that characterized the Wisconsinan period. During the warmer and drier waning glacial and intersticial stages the river laterally accreted its valley entrenched and widened in the preceding glacial stage. With the advent of the next intermediate glacial episode, the increasing discharge then overflowed the channel restricted by its deposits. The river then entrenched and widened the valley in preparation for the next aggravation phase. A radiometric age determined from concrete nodules in the upper soils suggests middle Wisconsinan culmination of this episode of terrace formation. The alloformation-2, occurring as a sandy and muddy soil disconformably overlying the overbank deposits of alloformation-2 at the TAMU Geotechnical Clay and RS-5 porthole sites, is inferred to have resulted from middle-late Wisconsinan age overbank flooding that preceded the entrenchment and widening of the Deweyville phase channel. Two of the cores contained distinct anomalous gravelly-clay deposits underlying the gravelly-sand to sand fining upward channel deposits. The presence of these deposits at the base of otherwise fining upward sequences provides an additional component to the classic fining upward model for channel deposits. These thank slump deposits' most probably were emplaced by bank failures occurring at or shortly after the beginning of the waning flood stage, which allowed for their preservation under the channel deposits laid down by the receding river. |
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| Item Description: | Vita. "Major Subject: Geology". |
| Physical Description: | xi, 147 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 89-103). |