Southeast Bering Sea Research Articles

Sources and dispersal patterns of clay minerals in surface sediments from the continental-shelf areas off Alaska

The Three mineral suites were recognized in the Gulf of Alaska. The glaciomarine sediments of fjords and the eastern shelf consist typically of the primary phyllosilicates, micas, and chlorites, derived locally from argillite, graywacke, and metavolcanics under conditions of mild chemical weathering. More glycol-expandable clay minerals (GECM) in the north Gulf substantiate clay supply to that region primarily from the Yakataga and Poul Creek Formations, and to a lesser extent from the Copper River. The northern Gulf clay-mineral suite is transported to central Prince William Sound and northeast Kodiak Shelf by the Alaska coastal current. In the western Gulf, clay minerals adjacent to the Alaska Peninsula are derived principally from the Susitna River via Cook Inlet, whereas those of the outer shelf presumably have their provenance in Kodiak Island and the Katmai Ash submarine deposit. In the southeast Bering Sea, a progressive northwestward decrease in GECM, from 65% to 11%, is caused by a gradually decreased sediment export from the Alaska Peninsula and the Aleutians, with a possible minor increase in illite from the Kuskokwin River. The Yukon River is the predominant clay source for the north Bering Sea, as signified by an abrupt increase in that area of GECM (20% to 35%) and of kaolinite/chlorite ratios. Clay mineralogy indicates that the central Chukchi Sea is the major repository of the Yukon clays, suggesting that clay-mineral stratigraphic studies have implications for interpretation of the Quaternary paleogeography of “Beringia.” In the Beaufort Sea nearshore, influence of different fluvial inputs and their dispersals by currents are sharply defined. The lack of a definite pattern to the distribution of clay minerals in the outer continental shelf may be due to haphazard transport of clays by ice rafting and/or reworking and redistribution of sediments resulting from ice gouging of the sea substrate. Movement of sediment to the west in the Alaskan portion of the inner shelf of Beaufort Sea is evident. An apparent seaward increase in illite/GECM ratio in the Colville Delta is tentatively ascribed to regeneration of degraded illite-micas by K + fixation in saline waters. An isolated area of sediment rich in expandable clay minerals in the central Beaufort Shelf presumably is relict.

Oceanography of the eastern Bering Sea ice‐edge zone in spring1

The ice‐edge region of the southeast Bering Sea was studied in terms of the hydrographic regime, phytoplankton biomass, and primary productivity during the springs of 1975 through 1977. The results showed that a phytoplankton bloom occurs at the ice edge just as the spring ice‐decay period begins, and that this accounts for a significant proportion of the annual carbon input over the shallow shelf. The bloom is intensified in time and space by the influence of the ice edge on the physical structure of the water column. Specifically, melting ice seems to increase the stability of the water column, near and under the ice, by lowering the salinity. Frontal structure in salinity and temperature are apparent at the ice edge and are attributed to the melting ice but also, at times, to wind‐driven Ekman‐type upwelling.These data are also related to recent short term (ca. months‐year) climatic fluctuations that seem to control the seasonal position of the ice‐edge zone relative to the shelf break. In “cold” years, the ice edge comes southward to the shelf break and overlies the more nutrient‐rich Alaska Stream/Bering Sea source water. In “warm” years, the ice‐edge zone does not reach this nutrient‐rich water. This may be important to the biology of the ice‐edge ecosystem.

An analysis of the influence of ice on spring phytoplankton population structure in the southeast Bering Sea1

Phytoplankton populations in the southeast Bering Sea were examined with respect to the influence of ice on population structure. Techniques of numerical analysis were applied to the data collected from 109 stations over a 3‐year period. Two major groups were present in spring—an ice‐edge group and a shelf‐break group. Our results suggest that the ice‐edge spring bloom is a distinct but short‐lived community, and that ice flora may act as an inoculum early in the spring bloom.

On Lateral Water Mass Interaction—A Case Study, Bristol Bay, Alaska

Abstract Salinity-temperature-depth data obtained on several spring and summer cruises during 1976 and 1977 from outer Bristol Bay in the southeast Bering Sea indicate the existence of a zone, between two well-defined water masses, where details of the interaction process are observable. This interaction zone is approximately 100–150 km wide and is characterized by a plethora of mid-water-column finestructure, in both temperature and salinity, that exhibit a hierarchy of vertical scale sizes. Vertical mixing energy within the zone appears low, which results in persistence of interleaving signatures induced by horizontal interaction of the two adjacent water masses. Such interaction probably occurs between all laterally juxtaposed water masses of nearly the same density; outer Bristol Bay allows enhanced examination of the process because of the broad lateral extent of the transition zone.

Multichannel CDP seismic reflection data acquired

The National Geophysical and Solar‐Terrestrial Data Center has recently acquired more than 3400 nautical miles of multichannel common depth point (CDP) seismic reflection data in Alaskan offshore waters.CDP seismic sections are available for a number of survey lines in the Gulf of Alaska, Cook Inlet, and the southeast Bering Sea. In general, the following formats are available: sections and location maps, in sepia or black line; velocity profiles and observer logs, on 35‐mm microfilm; and technical report, shot‐point locations, on microfiche.

Bristol Bay: Model Contemporary Graded Shelf

A veneer of contemporary sediments covers the continental shelf in the Bristol Bay region of the southeast Bering Sea. The continental shelf is broad, covering an area of 1,500,000 sq/km, and has a relatively smooth bottom and a gentle slope of about 2.4 percent. Nearshore sediments are extremely poorly sorted gravelly sands which grade to well-sorted fine sands in the central bay. The far offshore sediments are extremely poorly sorted muddy sands. The mean size of the sediments generally decreases with increasing depth and distance from the coast. An overall decrease in the weight percent of total heavy mineral contents also is observed from the coast to the outer bay. The mineralogy of the sand reflects a complex provenance--sedimentary, high-grade metamorphic and igneo s sources in the north and east, and a volcanic source in the south. The heavy mineral dispersal pattern presumably is influenced by fluvial and marine currents. The general paucity of clay minerals and the dominance of feldspars in the less than 2-micron fractions of Bristol Bay sediments indicate the absence of intense chemical weathering in the source areas. Organic carbon content in the sediments is uniformly low (0.5 percent), and is closely related to the amount of clays in the sediments. On the basis of scatterplots of grain-size parameters, the Bristol Bay shelf can be delineated into two broad depositional environments, the inner and the outer shelves. Textural differences in the two environments are believed to be caused by storm-generated waves. These waves may be as great as 200 m long and are believed to elutriate the silts and clays from sediments up to a depth of 80 m. Grading of the shelf also is achieved principally by these waves that bring about a net seaward movement of nearshore sediments.

Recent Sedimentation on Southern Bering Shelf: ABSTRACT

A veneer of contemporary sediments covers the entire continental shelf in the Bristol Bay region of the southeast Bering Sea. This broad shelf, covering an area of 1.5 × 105 sq km has a relatively smooth bottom and gentle slope of about 1:4,000. Nearshore sediment is gravelly, coarse sand which grades to fine sand offshore. In general, the mean size of the sediment is related to the depth. The nearshore and offshore heterogenous sediments are very poorly sorted whereas homogeneous sand in the center is well sorted. The mineralogy of sand is diverse, reflecting the complex sources: sedimentary, metamorphic, and igneous terrane of the hinterland in the north and east, and typically volcanics from the Aleutian Islands in the End_Page 2503------------------------------ south. The general paucity of clay minerals and dominance of feldspars in size fraction The sediment character and distribution in Bristol Bay reflects two distinct sedimentary environments of deposition. Sediments on the shallow shelf are controlled by the storm-generated-wave drift currents, are moderately well sorted, and are devoid of silt and clay. In protected bays, and at water depths prohibiting elutriation by storm waves, the silt-clay content in sediments increases significantly. Local influences of fluvial, tidal, and wind-driven currents on sediments are also apparent. Long waves generated by frequent storms roil shelf sediments with a net seaward movement. The absence of silt and clay sediments and abundance of fine sand on the shelf and seaward prograding blankets of mud near the slope reflect midstage of shelf grading. Sedimentation in Bristol Bay shelf ma well be an analogue to the widespread, uniform epicontinental clastic deposits that were formed in the past. End_of_Article - Last_Page 2504------------

Peculiarities of ichthyofauna distribution in the South-east Bering Sea (In Russian; Eng. summary) : Shuntov, V. P., 1963 Zool. Zh., 42 (5): 704–715

Peculiarities of ichthyofauna distribution in the South-east Bering Sea (In Russian; Eng. summary) : Shuntov, V. P., 1963 Zool. Zh., 42 (5): 704–715