Image from page 676 of "The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder" (1981)
Title: The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder
Identifier: easternberingsea00hood
Authors: Hood, D. W. (Donald Wilbur), 1918-; Calder, John A; United States. Office of Marine Pollution Assessment; United States. Bureau of Land Management
Subjects: Oceanography Bering Sea.
Contributing Library: Penn State University
Digitizing Sponsor: LYRASIS Members and Sloan Foundation
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Physical and biological sedimentary structures 1289 HIGH ENERGY (INNER) SHELF LOW ENERGY (OUTER) SHELF
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UJ t- CO < III l- a o CD Figure 70-16. Conceptual model showing importance of physical structures versus biological structures in shelf sediments. Thickness of wedge depicts relative intensity of process from high-energy to low-energy shelf environments. Current and wave fields could be of various sizes depending on current or wave domination of a given shelf. All areas of physical structures would shift seaward with higher energy (see arrow) or toward shore with lower energy. Unidirectional current features on shelves will be more common seaward of nearshore wave structures, but the frequency of structures will relate to current intensity rather than distance seaward (for example, see Fig. 70-7). dates of 1,740 to 5,085 b.p. are found for bulk organic carbon in the top 1-2 cm of modem surface sediment on the northern Bering shelf (Teledyne Isotopes 1-8134, 8135, 8226, Fig. 70-6f). Radiocarbon dating of calcium carbonate of shells again suggests significant biologic mixing of modern shells downward into buried transgressive gravel and sand (Fig. 70-6b, c, h, and i). Fossil surface-dwelling mollusk species are just several hundred years old, even though only those shells buried in older sedi- ment far below the organisms' normal living habitat were dated (M. Rubin, USGS Radiocarbon Lab. W-2462, 2464, 2466, 2467, 2681-2685). In Chirikov Basin, where the transgressive sequences are thin and dating of shells does not appear to be reliable, mixed modem and transgressive foraminiferal assemblages are found throughout the entire transgressive se- quences (Figs. 70-8a and d; R. Echols, personal communication). Only where high sedimentation rates produce rapid, deep burial, as happens near the modem Yukon subdelta, do radiocarbon dates of shells and organic carbon agree with stratigraphy (M. Rubin, USGS, Radiocarbon Lab. W-26180; Teledyne Isotopes 1-7316, 8134); here unmixed transgressive sequences of microfossils can be detected. Rhoads (1970) points out another aspect of bio- turbation that may have particular geologic signifi- cance for the northeastern part of the Bering shelf. The predominance of deposit feeders cam reduce the bulk density of fine-grained sediment and greatly enhance the potential for erosion. The dominance of deposit feeders in Norton Sound (Figs. 70-10 and 70-11) (Rowland 1972) may contribute to the resuspension of considerable fine-grained sediment
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Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
Image from page 676 of "The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder" (1981)
Title: The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder
Identifier: easternberingsea00hood
Authors: Hood, D. W. (Donald Wilbur), 1918-; Calder, John A; United States. Office of Marine Pollution Assessment; United States. Bureau of Land Management
Subjects: Oceanography Bering Sea.
Contributing Library: Penn State University
Digitizing Sponsor: LYRASIS Members and Sloan Foundation
View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.
Text Appearing Before Image:
Physical and biological sedimentary structures 1289 HIGH ENERGY (INNER) SHELF LOW ENERGY (OUTER) SHELF
Text Appearing After Image:
UJ t- CO < III l- a o CD Figure 70-16. Conceptual model showing importance of physical structures versus biological structures in shelf sediments. Thickness of wedge depicts relative intensity of process from high-energy to low-energy shelf environments. Current and wave fields could be of various sizes depending on current or wave domination of a given shelf. All areas of physical structures would shift seaward with higher energy (see arrow) or toward shore with lower energy. Unidirectional current features on shelves will be more common seaward of nearshore wave structures, but the frequency of structures will relate to current intensity rather than distance seaward (for example, see Fig. 70-7). dates of 1,740 to 5,085 b.p. are found for bulk organic carbon in the top 1-2 cm of modem surface sediment on the northern Bering shelf (Teledyne Isotopes 1-8134, 8135, 8226, Fig. 70-6f). Radiocarbon dating of calcium carbonate of shells again suggests significant biologic mixing of modern shells downward into buried transgressive gravel and sand (Fig. 70-6b, c, h, and i). Fossil surface-dwelling mollusk species are just several hundred years old, even though only those shells buried in older sedi- ment far below the organisms' normal living habitat were dated (M. Rubin, USGS Radiocarbon Lab. W-2462, 2464, 2466, 2467, 2681-2685). In Chirikov Basin, where the transgressive sequences are thin and dating of shells does not appear to be reliable, mixed modem and transgressive foraminiferal assemblages are found throughout the entire transgressive se- quences (Figs. 70-8a and d; R. Echols, personal communication). Only where high sedimentation rates produce rapid, deep burial, as happens near the modem Yukon subdelta, do radiocarbon dates of shells and organic carbon agree with stratigraphy (M. Rubin, USGS, Radiocarbon Lab. W-26180; Teledyne Isotopes 1-7316, 8134); here unmixed transgressive sequences of microfossils can be detected. Rhoads (1970) points out another aspect of bio- turbation that may have particular geologic signifi- cance for the northeastern part of the Bering shelf. The predominance of deposit feeders cam reduce the bulk density of fine-grained sediment and greatly enhance the potential for erosion. The dominance of deposit feeders in Norton Sound (Figs. 70-10 and 70-11) (Rowland 1972) may contribute to the resuspension of considerable fine-grained sediment
Note About Images
Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.