Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska
Includes bibliographical references (pages 92-98) California State University, Northridge. Department of Geology. Analysis of 201 surface samples from the continental shelf of southeastern Bristol Bay, Alaska, has yielded an interpretation of the processes responsible for the distribution of sedimen...
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Language: | English |
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California State University, Northridge
1983
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Online Access: | http://hdl.handle.net/10211.3/128747 |
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ftcalifstateuniv:oai:dspace.calstate.edu:10211.3/128747 |
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openpolar |
institution |
Open Polar |
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California State University (CSU): DSpace |
op_collection_id |
ftcalifstateuniv |
language |
English |
topic |
Geology--Alaska Bristol Bay (Alaska) Sediment |
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Geology--Alaska Bristol Bay (Alaska) Sediment Johnson, Elizabeth A. Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska |
topic_facet |
Geology--Alaska Bristol Bay (Alaska) Sediment |
description |
Includes bibliographical references (pages 92-98) California State University, Northridge. Department of Geology. Analysis of 201 surface samples from the continental shelf of southeastern Bristol Bay, Alaska, has yielded an interpretation of the processes responsible for the distribution of sediment composition and texture {mean grain size, standard deviation, skewness, and kurtosis) in the region. The area had been previously described by Sharma {1974, 1975, 1979) and Askren (1972) as a classical graded shelf or one where sediment mean grain size becomes smaller with increased water depth. With the increase in number of samples studied and the increased sample density of this report, it is apparent that the previously described classically graded condition does not exist. Generally, the southeastern Bristol Bay shelf exhibits regional trends of a decrease in sediment-mean-grain-size and an increase in standard deviation, skewness, and kurtosis with increasing water depth. This scheme, however, is disturbed by areas of high variation in sediment textural measures. The pattern seems to be a relict of Pleistocene low-sea level graded outwash plain deposition which has subsequently been modified by wind-generated ocean waves and local ocean currents. During Pleistocene low-sea levels, the termini of Alaskan mainland continental glaciers were located near the present-day Bristol Bay shoreline. As sea level rose, the outwash plain deposits were covered by water. Submerged outwash plain deposits were further modified by hydrologic processes. Today, wind-generated waves, through progressive sorting, are entraining and transporting the relict outwash plain deposits and present day input. Some day they may reach a position of equilibrium between the hydraulic forces and the grain size, shape, and density. On a more local scale, ocean currents produced by a combination of high velocity tidal currents, storm-generated wind waves, water mass constriction, helical flow, and the Coriolis effect have produced currents which have scoured the shelf. Scours are a common feature and their effect on the regional sedimentation pattern is one of disruption. The scouring process selectively erodes surficial sediment, concentrating coarse mateial and removing fines, while leaving adjacent areas relatively undisturbed. Presently, the igneous terrain of the Alaska Peninsula and Unimak Island appears to be the only source of sediments seen in the study area. Surficial sediments have relatively high amounts of titaniferrous magnetite, basaltic hornblende, and volcanic rock fragments. The euhedral and angular nature of the sand grains indicates a short distance of transport. The rate of deposition on the shelf is low, due to an absence of any large sediment input into the area. Assuming a low sedimentation rate, sediments obtained from the uppermost 25 em of the shelf are both Holocene and Pleistocene in age. |
author2 |
Molina, Bruce F. Geological Sciences Gutstadt, Allan Squires, Richard |
format |
Thesis |
author |
Johnson, Elizabeth A. |
author_facet |
Johnson, Elizabeth A. |
author_sort |
Johnson, Elizabeth A. |
title |
Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska |
title_short |
Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska |
title_full |
Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska |
title_fullStr |
Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska |
title_full_unstemmed |
Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska |
title_sort |
textural and compositional sediment characteristics of the southeastern bristol bay continental shelf, alaska |
publisher |
California State University, Northridge |
publishDate |
1983 |
url |
http://hdl.handle.net/10211.3/128747 |
genre |
glaciers Alaska |
genre_facet |
glaciers Alaska |
op_relation |
http://hdl.handle.net/10211.3/128747 |
op_rights |
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ftcalifstateuniv:oai:dspace.calstate.edu:10211.3/128747 2023-05-15T16:22:37+02:00 Textural and compositional sediment characteristics of the Southeastern Bristol Bay Continental Shelf, Alaska Johnson, Elizabeth A. Molina, Bruce F. Geological Sciences Gutstadt, Allan Squires, Richard 1983-05 http://hdl.handle.net/10211.3/128747 en eng California State University, Northridge http://hdl.handle.net/10211.3/128747 http://scholarworks.csun.edu/xmlui/handle/10211.2/286 By signing and submitting this license, you the author grant permission to UniversityName Graduate Studies to submit your thesis or dissertation, and any additional associated files you provide, to RepositoryName, the institutional repository of the UniversityName, on your behalf.You grant to RepositoryName the non-exclusive right to reproduce and/or distribute your submission worldwide in electronic or any medium for non-commercial, academic purposes. You agree that RepositoryName may, without changing the content, translate the submission to any medium or format, as well as keep more than one copy, for the purposes of security, backup and preservation. You represent that the submission is your original work, and that you have the right to grant the rights contained in this license. You also represent that your submission does not, to the best of your knowledge, infringe upon anyone's copyright. If the submission contains material for which you do not hold copyright, or for which the intended use is not permitted, or which does not reasonably fall under the guidelines of fair use, you represent that you have obtained the unrestricted permission of the copyright owner to grant RepositoryName the rights required by this license, and that such third-party owned material is clearly identified and acknowledged within the text or content of the submission. If the submission is based upon work that has been sponsored or supported by an agency or organization other than the UniversityName, you represent that you have fulfilled any right of review or other obligations required by such contract or agreement. RepositoryName will clearly identify your name(s) as the author(s) or owner(s) of the submission, and will not make any alterations, other than those allowed by this license, to your submission. Geology--Alaska Bristol Bay (Alaska) Sediment Thesis 1983 ftcalifstateuniv 2022-04-13T11:14:26Z Includes bibliographical references (pages 92-98) California State University, Northridge. Department of Geology. Analysis of 201 surface samples from the continental shelf of southeastern Bristol Bay, Alaska, has yielded an interpretation of the processes responsible for the distribution of sediment composition and texture {mean grain size, standard deviation, skewness, and kurtosis) in the region. The area had been previously described by Sharma {1974, 1975, 1979) and Askren (1972) as a classical graded shelf or one where sediment mean grain size becomes smaller with increased water depth. With the increase in number of samples studied and the increased sample density of this report, it is apparent that the previously described classically graded condition does not exist. Generally, the southeastern Bristol Bay shelf exhibits regional trends of a decrease in sediment-mean-grain-size and an increase in standard deviation, skewness, and kurtosis with increasing water depth. This scheme, however, is disturbed by areas of high variation in sediment textural measures. The pattern seems to be a relict of Pleistocene low-sea level graded outwash plain deposition which has subsequently been modified by wind-generated ocean waves and local ocean currents. During Pleistocene low-sea levels, the termini of Alaskan mainland continental glaciers were located near the present-day Bristol Bay shoreline. As sea level rose, the outwash plain deposits were covered by water. Submerged outwash plain deposits were further modified by hydrologic processes. Today, wind-generated waves, through progressive sorting, are entraining and transporting the relict outwash plain deposits and present day input. Some day they may reach a position of equilibrium between the hydraulic forces and the grain size, shape, and density. On a more local scale, ocean currents produced by a combination of high velocity tidal currents, storm-generated wind waves, water mass constriction, helical flow, and the Coriolis effect have produced currents which have scoured the shelf. Scours are a common feature and their effect on the regional sedimentation pattern is one of disruption. The scouring process selectively erodes surficial sediment, concentrating coarse mateial and removing fines, while leaving adjacent areas relatively undisturbed. Presently, the igneous terrain of the Alaska Peninsula and Unimak Island appears to be the only source of sediments seen in the study area. Surficial sediments have relatively high amounts of titaniferrous magnetite, basaltic hornblende, and volcanic rock fragments. The euhedral and angular nature of the sand grains indicates a short distance of transport. The rate of deposition on the shelf is low, due to an absence of any large sediment input into the area. Assuming a low sedimentation rate, sediments obtained from the uppermost 25 em of the shelf are both Holocene and Pleistocene in age. Thesis glaciers Alaska California State University (CSU): DSpace |